a r X i v :c o n d -m a t /0103480v 1 [c o n d -m a t .s u p r -c o n ] 23 M a r 2001
Electron Dynamics in Nd 1.85Ce .15CuO 4+δ:Evidence for the Pseudogap State and
Unconventional c-axis Response
E.J.Singley,D.N.Basov
Department of Physics University of California San Diego,La Jolla,CA 92093-0319
K.Kurahashi ?,T.Uefuji,K.Yamada
Institute for Chemical Research,Kyoto University,Uji 611-0011,Japan
Infrared re?ectance measurements were made with light polarized along the a-and c-axis of both superconducting and antiferromagnetic phases of electron doped Nd 1.85Ce .15CuO 4+δ.The results are compared to characteristic features of the electromagnetic response in hole doped cuprates.Within the CuO 2planes the frequency dependent scattering rate,1/τ(ω),is depressed below ～650cm ?1;this behavior is a hallmark of the pseudogap state.While in several hole doped compounds the energy scales associated with the pseudogap and superconducting states are quite close,we are able to show that in Nd 1.85Ce .15CuO 4+δthe two scales di?er by more than one order of magnitude.Another feature of the in-plane charge response is a peak in the real part of the conductivity,σ1(ω),at 50-110cm ?1which is in sharp contrast with the Drude-like response where σ1(ω)is centered at ω=0.This latter e?ect is similar to what is found in disordered hole doped cuprates and is discussed in the context of carrier localization.Examination of the c-axis conductivity gives evidence for an anomalously broad frequency range from which the interlayer super?uid is https://www.doczj.com/doc/1d7966594.html,pelling evidence for the pseudogap state as well as other characteristics of the charge dynamics in Nd 1.85Ce .15CuO 4+δsignal global similarities of the cuprate phase diagram with respect to electron and hole doping.
I.INTRODUCTION
The family of high temperature superconductors A 2?x Ce x CuO 4,where A is a rare earth ion (Nd,Pr,Sm,Eu),has historically been considered an exception among copper oxides.Like all cuprates the basic build-ing blocks of the structure are the CuO 2layers.An im-portant di?erence is that in the superconducting phases of A 2?x Ce x CuO 4lack the apical oxygen above the in-plane copper atom found in most hole doped cuprates.The charge carriers in A 2?x Ce x CuO 4are electrons rather than holes as in all other cuprate families.1,2These mate-rials have a relatively low T c and early microwave mea-surements suggested the order parameter was s -wave 3in contrast with the d -wave symmetry established for hole doped compounds.However,more recent microwave measurements 4,5,along with photoemission 6,and phase sensitive experiments 7indicate that the order parameter in Nd 1.85Ce .15CuO 4+δ(NCCO)and Pr 1.85Ce .15CuO 4+δmay in fact be d -wave.The most comprehensive infrared work on superconducting NCCO by Homes et al.8found weak electron-phonon coupling below T c ,suggesting that NCCO,like other cuprates,is not a phonon-mediated su-perconductor.However,in contrast to other cuprates the in-plane super?uid was found to be anomalously large for a low T c material,causing NCCO to deviate signi?cantly from universal Uemera plot 9.These results leave the nature of the relation between electron and hole doped cuprates ambiguous.
Previous doping dependent infrared studies have found that the evolution of spectral weight from the insulting parent compounds through the superconducting phases
is similar in both electron and hole doped cuprates.10–12Doping ?rst moves spectral weight from above the charge transfer gap to the mid-infrared,and then to the Drude peak at ω=0.This implies that whether doped with electrons or holes the Mott-Hubbard insulator shows the same gross features in the electronic conductivity.De-tailed studies on a variety of hole doped cuprates reveal a partial gap (pseudogap)in the spectrum of the low en-ergy excitations.13The pseudogap state is recognized as one of the key characteristics of the (hole doped)cuprates and is believed to be intimately connected to the origin of high-T c superconductivity.14So far,there have been no reports for a similar pseudogap region on the elec-tron doped side of the phase diagram.15With this in mind it is critical to determine whether there are prin-cipal di?erences in the fundamental interactions de?ning carrier dynamics and superconductivity in electron and hole doped Mott-Hubbard insulators.In short the ques-tion ”Is NCCO a high temperature superconductor?”17needs to be re-visited.
In this work we have determined the optical constants of Nd 1.85Ce .15CuO 4+δfor both the as grown antiferro-magnetic (AF)phase and oxygen reduced superconduct-ing (SC)samples.Special attention is paid to the low energy (ω<100meV)physics.Through an analysis of the in-plane scattering rate,1/τ(ω),we ?nd compelling evidence for a pseudogap in the electron doped materials.The doping and temperature dependence of the pseudo-gap is shown to mirror the behavior found in hole doped cuprates.Another important result is concerned with the non-monotonic behavior of σ1(ω)in the far-infrared which is similar to that of disordered hole doped cuprates
and suggests charge carrier localization.We have also examined the interlayer c-axis conductivity of NCCO.A sum rule analysis demonstrates that nearly all of the in-terlayer super?uid is accumulated from an energy scale in excess of8?,where?is the superconducting gap. This paper is organized in the following manner.Sec-tion II gives a brief overview of the experimental pro-cedures.The raw R(ω)data and the Kramers-Kronig generatedσ1(ω)for both the a-and c-axis of the SC and AF samples are presented in Section III.Section IV fol-lows with a discussion of the key results.In sub-section IV-A we establish the existence of a pseudogap through the analysis of the in-plane scattering rate and discuss the implications of this result.Next,evidence for local-ization in the cuprates is presented in sub-section IV-B, and we elaborate on the impact of localization on both the DC and AC transport properties.Finally,sub-section IV-C discusses the energy scale related to the interlayer super?uid response.We conclude by summarizing our results in section V.
II.EXPERIMENTAL PROCEDURE
Single crystals of NCCO were prepared by the traveling-solvent-?oating-zone method.18The as-grown crystals are not superconducting,but show antiferromag-netic order with T N=125K-160K.19Superconduc-tivity is achieved by deoxygenating the crystals.This process removes a small amount of apical oxygen atoms which are absent in the ideal T’structure.20
The near normal re?ectance was measured in polarized light from the far-infrared(FIR)to the near-ultraviolet.
A Fourier transform spectrometer was used from10cm?1 to18,000cm?1,and a grating monochramotor was used from12,000cm?1to48,000cm?1.After the re?ectance was measured at various temperatures,the sample was coated in-situ with gold or aluminum and the measure-ments were repeated at all temperatures,providing an absolute measure of the re?ectivity.21The error in the absolute value of the re?ectance is below1%.The rel-ative error in the re?ectance measured at di?erent tem-peratures does not exceed0.1%.
To obtain the complex optical constants the Kramers-Kronig relations were used.In order to extend the re?ectance data to higher energies the re?ectance of Pr1.85Ce.15CuO4from6eV to38eV was adopted.22 Above38eV the functional form R∝ω?4was assumed. When extrapolating the re?ectance to zero frequency a Hagen-Rubens model was applied in the normal state, and a two-?uid model in the superconducting state.The error in the re?ectance has been propagated to the optical constants and combined with uncertainties introduced by the extrapolation procedure,and will be discussed in the text.
III.REFLECTIVITY MEASUREMENTS AND KRAMERS-KRONIG ANALYSIS
A.a-axis
Fig.1shows the a-axis re?ectance of the SC(Panel A)and AF(Panel B)samples in the FIR.The292K spectrum of the SC sample shows metallic behavior with a single phonon at300cm?1.There is additional weak structure between400cm?1and700cm?1which grows
in intensity as the sample is cooled.The re?ectance of the SC sample shows a strong temperature dependence in the FIR.By25K the re?ectance is nearly5%above that at room temperature.Between150cm?1and300 cm?1the re?ectance of the SC sample at25K rivals that of such excellent conductors as Cu,Al,and Au yet the DC transport measurements indicate that the sample is a rather poor conductor.23–25The resolution of this am-biguity can be found in the re?ectance data below150 cm?1.Instead of R(ω)approaching1monotonically as ω→0as in a metal,the re?ectance decreases giving rise to a peak in R(ω).As will be demonstrated later, this is a consequence of having poor conductivity atω=0 which greatly increases at?nite frequencies.One?nal peculiarity of the SC sample is the lack of temperature dependence below T c.The superconducting(7K)re-?ectance increased slightly below100cm?1,but at all higher frequencies the spectra was identical to the data at T c(25K)within0.1%.The fact that the sample is truly a bulk superconductor can be con?rmed by Fig.4 were the c-axis re?ectance changes dramatically below T c.
The FIR re?ectance of the AF sample(Panel B)is qualitatively di?erent from it’s SC counterpart.The re-?ectance is lower at all temperatures and drops more quickly with increasing frequency.Notice that the y-axis of the top panel covers only8%while the bottom panel extends from85%-100%.The phonon mode seen at 300cm?1is still clearly visible here.Three other modes that have been previously reported16can also be iden-ti?ed at130,340,and510cm?1.In addition a broad ”hump”structure extending from250-450cm?1is ob-served which grows in intensity as the temperature is low-ered.No downturn in R(ω→0)is observed and at low temperatures R(ω<300cm?1)is nearly independent of frequency.
The right panel of Fig.1(C)shows the a-axis re-?ectance over an extended frequency range for both the SC and AF samples at292K and25K.The dominant feature of R(ω)in both samples is a plasma minimum at ω～11,000cm?1.The re?ectance of the SC sample is ～10%higher than that of the AF sample in the mid-infrared,but drops below it near the plasma minima.In the SC sample R(ω)at25K smoothly joins the room temperature re?ectance before the plasma minimum.In contrast to this behavior,in the AF sample the25K R(ω)curve crosses the292K spectrum at1,000cm?1
and in the low temperature spectrum reveals a partial gap-like depression at ω<4,000cm ?1.This structure has previously been reported by Onose and coworkers.16Fig.2shows the real part of the conductivity,σ1(ω),for the a-axis of the SC sample generated from the R(ω)data in Fig.1.The most prominent feature is the peak in σ1(ω)below 100cm ?1.This should be contrasted with the behavior of conventional metallic systems which can be described by the Drude model:
σD 1(ω)
=
ω2
p τ
ρs /?∞,where ρs ∝
n s /m ?
and n s is the density of paired electrons and m ?is their e?ective mass.The re?ectance can be expressed in terms of the dielectric function as:R(ω)=(√√
ρs =26μm.This value is con?rmed
by an analysis of the dielectric function generated from a Kramers-Kronig transformation of R(ω).Along these same lines we can gain an estimate for the DC conductiv-
ity at T
c directly from R(ω).We model the upturn seen in the re?ectance of the 25K spectrum as ω→0with ?an
d Eq.1.A reasonabl
e assumption for the spectra seen in Fig.5is 1/τ?100cm ?1,therefore there is only one
free parameter,ω2
p τ=σDC ,and we obtain an excellent ?t to the data with σDC =1.5??1cm ?1(dotted line).The right panel of Fig.5shows σ1(ω)obtained from Kramers-Kronig transformation of R(ω)for the SC sam-ple.The frequency range is con?ned to the region below the ?rst phonon mode (ω<120cm ?1).The electronic
contribution to the conductivity is extremely weak.For example,σ1(ω=10cm ?1)=1.5??1cm ?1at 25K,which is the same value as was obtained from the ?t of R(ω)in the left panel.Below T c the temperature dependence of the low frequency conductivity is anomalous;at 10cm ?1σ1(T c )>σ1(T =7K),however by 50cm ?1σ1(T c )has dropped below the conductivity at 7K.Also notice that
σ1(T =19K)is greater than σ1(T c )throughout the en-tire frequency range depicted in Fig.5.
An example of the error in σ1(ω)is shown at 95cm ?1for the T =25K spectrum.The error was calculated by propagating the uncertainty in the re?ectance,and tak-ing into account variations caused by di?erent extrap-olations of the re?ectance to high and low frequencies.For the present analysis it is important to distinguish between absolute and relative errors.The absolute error
is shown by the large bars to be±1??1cm?1.The rel-ative error in the temperature dependence is an order of magnitude smaller and shown by the small bars.
IV.DISCUSSION
A.Electron dynamics in the CuO2plane:Pseudogap
A unique characteristic of the electron doped cuprates is the manner in which superconductivity is induced in the phase diagram.The as-grown crystals of Nd2?x Ce x CuO4+δprogresses from an insulator at x=0 to a metal at x=.21without the appearance of a su-perconducting phase.The superconducting state can only be realized by annealing the as-grown crystals in an oxygen free atmosphere.26While this procedure re-duces the oxygen content by only?1%27the changes inσ1(ω)through out the infrared are signi?cant.What can be drawn from Fig.2and Fig.3is that the AF sam-ple is under doped with respect to the SC sample.To quantitatively compare the di?erences inσ1(ω)Fig.6
showsσSC
1(ω)?σAF
1
(ω)below14,000cm?1.In the SC
sample the mid-infrared absorption is reduced,while the low frequency(ω<1,300cm?1)absorption increases. The inset shows the e?ective spectral weight,N eff(ω)= ω0σ1(ω′)dω′,for both the SC and AF sample.While the low energy spectral weight grows more quickly in the SC sample,N eff(ω)is nearly equal by12,000cm?1(?1.5eV)for the two materials.28This e?ect is similar to the result of Ce doping from x=.12to x=.2in oxygen reduced Pr2?x Ce x CuO4+δ.10The deoxyengenation pro-cess that takes the AF sample into the superconducting phase is similar to the doping processes in hole doped cuprates.Spectral weight is transferred to lower ener-gies which enhances the metallic response and induces superconductivity.
We now turn to the analysis of the evolution of elec-tron dynamics associated with changes of carrier density from the under doped(AF)region to the optimally doped (SC)sample.A useful optical constant within the con-text of this discussion is the frequency dependent scat-tering rate:29
1/τ(ω)=ω2p
σ(ω)
).(2)
In Fig.7we plot1/τ(ω)for both the AF sample(left panel)and the SC sample(right panel).Looking?rst at
the right panel we see that aboveω～650cm?11/τ(ω) varies nearly linearly withω.However,at lower frequen-
cies1/τ(ω)drops faster than this linear trend.The low frequency suppression is strongest at25K,yet persists even at room temperature.The top of the”shoulder”in 1/τ(ω)is chosen as the frequency,Θ,characterizing the low energy depression of1/τ(ω).
Turning to the AF sample we again see the low fre-
quency suppression of1/τ(ω)which is now much more pronounced.In addition,the magnitude of the scatter-ing rate is nearly twice that of the SC sample.However,
the characteristic frequency remains atΘ=650cm?1as in the SC sample.The frequency dependence of1/τ(ω)
also remains nearly linear aboveΘ,30but there is less temperature dependence in this region than found in the SC sample.
Several features of1/τ(ω)described above for NCCO
are characteristic of the pseudogap state in hole doped cuprates.13,29,31,32Fig.8shows typical1/τ(ω)spectrum for under and weakly over hole doped Bi2212.31Exam-ining?rst the under doped compound in the left panel, the most prominent feature is the depression of1/τ(ω) below?700cm?1in both the normal and superconduct-ing state.This depression is absent at292K were the linear high-ωtrend continues to the lowest frequencies, yet is clearly well developed at T>T c.This reduction of the scattering rate has been attributed to the opening of a partial gap,or pseudogap,in the density of states.In Bi2212and other hole doped cuprates the pseudogap has been shown to have the same d x2?y2symmetry and sim-ilar magnitude as the superconducting gap.33Turning to the over doped sample in the right panel we see that the feature in1/τ(ω)is now only observed in the supercon-ducting state.The overall magnitude of the scattering is much smaller,and at high frequencies1/τ(ω)is tempera-ture dependent.The doping dependent trends of1/τ(ω) are consistent with a variety of other measurements:13in the under doped phase a pseudogap opens at a temper-ature T?>T c,with an energy scaleΘ?2?,while the pseudogap is absent above T c in the over doped phase. Looking back at the NCCO data in Fig.7we can see several features that are common to1/τ(ω)in the hole doped cuprates.The onset of the depression in1/τ(ω) remains atΘ=650cm?1,independent of doping.The magnitude of1/τ(ω)is higher in the under doped sam-ples,and the onset of the depression is much sharper.As doping increases the low energy suppression of1/τ(ω)de-creases.In addition a strong temperature dependence is observed across the energy range displayed for the more heavily doped samples.There are a few marked di?er-ences with the NCCO data.First,1/τ(ω)in the su-perconducting state(not shown)is nearly identical to the25K spectrum above150cm?1.This is a result of an anomalously small super?uid density,as will be dis-cussed in the next section.The second main di?erence is that the depression in1/τ(ω)is observed at all tem-peratures,suggesting T?exceeds292K in both the AF and SC samples.This latter result may resolve a long standing discrepancy between the linear temperature de-pendent resistivity of optimally doped hole cuprates34 and the nearly quadratic temperature dependent resis-tivity in NCCO.In the pseudogap state(T
The observation of a pseudogap in NCCO(T c=25
K)with a characteristic temperature T?>300K,has signi?cant implications on our theoretical understand-ing of this phenomenon.In particular,our data sug-gest that the pseudogap may be distinct from the su-perconducting gap.Determining the relationship be-tween the pseudogap and superconducting state has be-come a central problem in the?eld of high temperature superconductivity.14Because many electronic and mag-netic properties such as Fig.8(left panel)and others33 evolve smoothly from the pseudogap to superconducting state,the pseudogap is often considered a precursor of the superconducting gap.In addition,the similarities of the energy scales associated with the pseudogap and su-perconducting states has also been used to support this view.In contrast,in the present experimental work these energy scales are much di?erent.The pseudogap energy scale,Θ,extracted from1/τ(ω)is roughly the same as found in the hole doped cuprates(about5-10%less). However,recent photoemission work6on NCCO indicate that the superconducting gap is as small as2??3meV, more than an order of magnitude smaller thanΘ.These data clearly suggest that in NCCO the pseudogap,as determined from1/τ(ω),is not the same as the super-conducting gap.Whether this conclusion will hold in other cuprate were the two energy scales are very similar will require further study.
A complimentary interpretation of the pseudogap structure in1/τ(ω)may be formulated in terms of charge carriers coupling to a collective mode.36,37At the energy of the mode a new channel of scattering opens for the charge carriers leading to an increase in1/τ(ω).38From an inversion of the1/τ(ω)curve the spectrum of the col-lective mode W(ω)can be estimated;39
W(ω)=1
dω2 ω1
dρ/dT).Conventionally the peak inσ1(ω)is accompa-nied by an activated DC transport.Moreover,the fre-quency of the peak inσ1(ω)agrees well with the acti-vation energy extracted from the resistivity data for2-D electron gas in Si?eld-e?ect transistors.50Neverthe-less,a coexistence of the”metallic”resistivity and the peak inσ1(ω)is a robust result reported for a variety of cuprates.This enigma can be qualitatively understood by considering the complexity of the Fermi surface in the cuprates.58The DC conductivity primarily probes the quasiparticles at the zone diagonal where the d-wave gap has nodes.The optical conductivity is also domi-nated by the nodal regions.However,electronic states at the zone boundaries[(π,0)or(0,π)]are also sam-pled through the IR measurements as evidenced through the observation of the d-wave pseudogap.29,32Accord-ing to recent photoemission results,with the systematic addition of impurities,states develop within the gap at (π,0).59This has recently been con?rmed through the observation of intra-gap resonance’s with scanning tun-neling microscopy.60We believe that these resonance’s may be connected with the peak observed inσ1(ω).At the same time the DC transport is e?ectively shunted by the highly mobile nodal quasiparticles and therefore re-mains relatively insensitive to the dramatic changes close to the zone boundary.
The e?ects of disorder are also expected to be promi-nent in the superconducting state.In a d-wave supercon-ductor disorder leads to pair breaking,61and will there-fore decrease the total amount of super?uid.Infrared studies have shown that with increasing disorder the su-per?uid density(ρs)is systematically depleted while a concomitant growth of the?nite frequency peak inσ1(ω) is observed.51,52In NCCO we also observe an anoma-lously small super?uid density.This can be demon-strated from the following sum rule:62
120
ρs=
by two components:
σs(ω)=σpair(ω)+σreg(ω).(5) The?rst term represents the paired carriers and is given
byσpair
1(ω)=ρsδ(ω=0)/8.The second term corresponds
to unpaired carriers below T c and
is plotted in the right
panel of Fig.5.Whileσpair
1(ω)is outside of the range of
our experiment,the formation ofρs which gives rise to
this term can be seen in the energy loss function,Im(-1/?),plotted in the inset of Fig.5.In a conducting ma-
terial the loss function shows a peak at a frequency pro-portional to the carriers plasma frequency.Looking at
the plot of Im(-1/?)we see that at T=T c(thin black line)the loss function is?at and featureless correspond-
ing to an over-damped plasmon.As the temperature is reduced below T c a sharp resonance develops signaling
the formation ofρs.
The development ofρs must be contrasted with the be-
havior ofσ1(ω)in Fig.5.From the sum rule in Eq.4we see that asρs increases there should be a corresponding
decreases inσ1(ω)at?nite frequencies.What is actu-ally observed is much di?erent.At19K,where the peak
in the loss function indicates a non-zero super?uid den-
sity,σ1(ω)is larger than the normal state curve at all frequencies shown in Fig.5.In fact above50cm?1the absorption is greater at all temperatures in the supercon-ducting state compared to the normal state curve at25
K.In order to better elucidate this behavior we rewrite Eq.4asρs=120
π ∞W c[σN1(ω)?σS1(ω)]dω.(6)?K represents the contribution toδ(0)from the experi-mentally inaccessible integration region.For the c-axis, above120cm?1the electronic component of the conduc-tivity is overwhelmed by the response of the phonons. Therefore the limit of integration is taken as W c=120 cm?1,which corresponds to～8?.6.While the absolute value of W c is small,it is worth noting that in all hole doped cuprates that have been studied,71,72σS1?σN1all ready at2?,and this equality continues throughout the experimentally available range(～20?).
The analysis of Eq.6reveals the energy scale of the electronic states that make up the superconducting con-densate.In order to determine the relative amount of ρs originating fromω>W c we de?ne the normalized missing spectral weight(NMSW)as?K(T)/ρs(T).This ratio gives the fraction of the totalδ-function spectral weight drawn fromω>W c=8?.The NMSW is plotted as a function of reduced temperature in Fig.12.This fraction is close to1below.5T c,but increases well above 1as T→T c.The inequality?K(T)/ρs(T)>1means that in addition to the growth ofρs atω=0,the?nite frequency spectral weight atω
In order to clarify the role of the cut-o?W c in the anal-ysis of the energy scales involved in the formation of the superconducting condensate we repeat our analysis with a model BCS system.In conventional superconductors which follow the BCS formalism the formation ofρs is always accompanied by a decrease in low frequency spec-tral weight at T
In BCS theory,there is only one energy scale in-volved in superconductivity:the superconducting gap,?.However,the data for NCCO suggests that?plays little if any role in determining the region from which ρs is collected.This indicates that there is an addi-tional energy scale which is greater than8?,in cuprate superconductors.70,77
Studies on the doping dependence of the NMSW in Tl2Ba2CuO6+δ79and YBa2Cu3O6+δ72have found this e?ect to be largest in under doped compounds.The conclusion drawn from these experiments is that when the normal state is incoherent,with low spectral weight, the super?uid is derived from high energies.As a more coherent response develops at low frequencies,the su-per?uid is formed from this spectral weight nearω= 0.The incoherent conductivity which drives the source ofρs to higher energies has been linked to the normal state pseudogap.72For technical reasons we were not able to observe a pseudogap in the c-axis conductivity of NCCO.80However,the extremely small values ofσ1(ω) along with the absence of any obvious Drude peak in the interlayer conductivity is consistent with strongly inco-herent transport.The source of the large NMSW shown in Fig.12is likely to be tied to the incoherent conduc-tivity as in the hole doped cuprates.
V.CONCLUSIONS
To conclude we?nd several similarities between NCCO and the hole doped cuprates.The analysis of1/τ(ω)in
the SC sample provides strong evidence for a pseudo-gap in the electron side of the cuprate phase diagram. In addition,the trends seen in the evolution of1/τ(ω) from the under doped AF sample to the optimally doped SC sample closely follow the behavior of the hole doped cuprates.In NCCO the pseudogap energy scaleΘis more than an order of magnitude greater than2?.This result implies that,at least in NCCO,the pseudogap and superconducting gap are not the same.
The peak seen in the in-plane conductivity,along with a low value ofρs is often observed in disordered hole doped cuprates.Disorder in low dimensional materials, such as the cuprates,often results in charge carrier local-ization.However,the non-trivial topology of the Fermi surface in the cuprates may lead to a coexistence of lo-calization features inσ1(ω)with metallic DC transport.
A sum rule analysis of the c-axis conductivity reveals similar trends as is observed in hole doped cuprates. Namely,the spectral weight that is transferred to the delta-function peak atω=0below T c originates from an energy range in excess of8?.This is fundamen-tally di?erent from the behavior of conventional super-conductors,and indicates a large energy scale is involved in superconductivity in both electron and hole doped cuprates.In addition a comparison of the normal and superconducting properties in NCCO clearly places it in the same universality class as the hole doped cuprates as opposed to other conventional layered superconductors. This work was supported by the NSF grant DMR-9875980and the Alfred P.Sloan Foundation.D.N.Basov is a Cotrell Fellow of the Research Corporation.
?Present address:Kohzu Seiki Co.,Setagaya1-8-19, Tokyo,Japan
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47M.A.Ordal,L.L.Long,R.J.Bell,S.E.Bell,R.R.Bell, R.W.Alexander, C.A.Ward,Applied Optics,221099 (1983)
48W.Gotze,P.Wol?e,PRB61226(1972)
49R.S.Kohlman and A.J.Epstein in Handbook of con-ducting polymers Ed.T.A.Skotheim,R.L.Elsenbaumer, J.R.Reynolds(M.Decker,New York1998)p.85
50S.J.Allen,D.C.Tsui,F.DeRosa,PRL351359(1975)
51D.N.Basov,A.V.Puchkov,R.A.Hughes,T.Strach,J.Pre-ston,T.Timusk,D.A.Bonn,R.Liang,W.N.Hardy,PRB 4912165(1994)
52D.N.Basov,B.Dabrowski,T.Timusk,PRL812132(1998) 53An alternative explanation for these results is that the systems are macroscopically inhomogeneous,consisting of metallic and insulating regions.The mixed phase system can give rise to a peak inσ1(ω).49
54C.Weber,D.N.Basov,R.Yoshazki,unpublished 55Other cuprates that have shown low frequency peaks in σ1(ω)in-clude Tl2Ba2CuO6+δ40,under doped La1.86Sr.14CuO441, the three layered compound HgBa2Ca2Cu3O8+δ42,the single layer Bi2Sr2CuO656,and the non-superconducting quasi1-D compound Sr1?x Ca x Cu24O4157.
56S.Lupi,P.Calvani,M.Capizzi,P.Roy,cond-mat/0001244 57T.Osafune,N.Motoyama,H.Eisaki,S.Uchida,S.Tajima, PRL821313(1999)
58Z.-X.Shen,W.E.Spicer, D.M.King, D.S.Dessau, B.O.Wells,Science267343(1995)
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60S.H.Pan,E.W.Hudson,https://www.doczj.com/doc/1d7966594.html,ng,H.Eisaki,S.Uchida, J.C.Davis,Nature403746(2000)
61R.J.Radtke,K.Levin,H.B.Schuttler,M.R.Norman,PRB 48653(1993);M.Franz,C.Kallin,A.J.Berlinsky,PRB 546897(1996)
62M.Tinkham,R.A.Ferrell,PRL2331(1959)
63It should be noted that there are substantial errors in the absolute value ofσ1(ω)near the peak.The absorption is proportional to1-R(ω),which from examination of Fig.1is very small at low temperatures.Therefore our error in the absolute values of R(ω)of±1%causes a large uncertainty inσ1(ω).For example,a reduction of the25K re?ectance by1%cuts the magnitude of the peak inσ1(ω)by50%. However,the relative error which is an order of magnitude smaller is the relevant error when applying Eq.4.Taking this error into consideration Eq.4still accounts for less than5%of the spectral weight corresponding to published values of the penetration depth.
64F.Gollnik,M.Naito,PRB5811734(1998)
65A.A.Nugroho,I.M.Sutjahja, A.Rusydi,M.O.Tjia, A.A.Menovsky, F.R.de Boer,J.J.M.Franse,PRB60 15384(1999)
66S.Chakravarty,A.Sudbo,P.W.Anderson,S.Strong,Sci-ence261337(1993);O.K.Andersen,A.I.Liechtenstein, O.Jepsen, F.Paulsen,J.Phys.Chem.Solids561573 (1995);T.Xiang,C.Panagopoulos,J.R.Cooper,Int.J. of Mod.Phy.B121007(1998)
67A.Pimenov, A.V.Pronin, A.Loidl,U.Michelucci, A.P.Kampf,S.I.Krasnosvobodtsev,V.S.Nozdrin, D.Rainer,cond-mat/0005515
68D.N.Basov,T.Timusk, B.Dabrowski,J.D.Jorgensen, PRB503511(1994)
69S.V.Dordevic, E.J.Singley, D.N.Basov,J.H.Kim, M.B.Maple,E.Bucher,cond-mat/0102455
70J.E.Hirsch,Physica C199305(1992)
71D.N.Basov,S.I.Woods, A.S.Katz, E.J.Singley, R.C.Dynes,M.Xu,D.G.Hinks,C.C.Homes,M.Strongin, Science28349(1999)
72D.N.Basov, C.C.Homes,M.Strongin, E.J.Singley, T.Timusk,G.Blumberg,D.van der Marel,to be published in PRB
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74S.Chakravarty,Eur.Phys.J.B5337(1998); S.Chakravarty,H.-Y.Kee,E.Abrahams,PRL822366
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75L.B.Io?e,https://www.doczj.com/doc/1d7966594.html,lis,Science2851241(1999)
76W.Kim,J.P.Carbotte,PRB62592(2000)
77M.Imada,S.Onoda,cond-mat/0008050
78The parameters used in this calculation are(1/τ)/(2?)= 10,and T=0.W.Zimmermann,E.H.Brandt,M.Bauer,
E.Seider,L.Genzel,Physica C18399(1991)
79A.S.Katz,S.I.Woods, E.J.Singley,T.W.Li,M.Xu,
D.G.Hinks,R.C.Dynes,D.N.Basov,PRB615930(2000) 80The observation of a pseudogap requires the analysis of the frequency dependence ofσ1(ω)throughout the FIR.Over most of this range the electronic contribution toσ1(ω)is overwhelmed by the phonon response,therefore completely masking any changes inσ1(ω)from the electronic channel.
FIG.1.Panel A:a-axis far-infrared re?ectance of the SC sample at T=292,225,150,80,25,and7K.As the temper-ature drops a well de?ned maximum develops at150cm?1. The temperature dependence below T c is con?ned toω<100 cm?1.Panel B:a-axis re?ectance of the AF sample at the above temperatures.Notice that the y-axis covers a broader range than in panel A.The overall re?ectance is lower than that of the SC sample and additional phonon modes are visi-ble.An anomalous structure between250cm?1and450cm?1 is visible at292K and grows in strength as the temperature is reduced.Panel C:high frequency re?ectance of the SC and AF sample at292K and25K.The screened plasma frequency (minimum in R(ω))is the same in both samples.While the 25K and292K spectrum merge smoothly in the SC sample, the25K curve in the AF sample crosses below292K at1,000 cm?1and remains suppressed up to4,000cm?1.
FIG.2.Far-infrared conductivity for the a-axis of the SC sample.At all temperatures there is a?nite frequency peak inσ1(ω).The peak grows in intensity and softens as the temperature is lowered to T c.Below T c the peaks intensity is slightly reduced as it further softens.The inset showsσ1(ω) at25K and292K up to4,000cm?1where the y-axis has been reduced by nearly an order of magnitude.The peak is clearly visible even at292K.The inset shows the canonical pseudogap behavior ofσ1(ω)as seen in the under doped hole cuprates.As the temperature decreases the low frequency peak narrows below a characteristic frequency(?650cm?1).
FIG.3.A-axis conductivity of the AF sample at25K and 292K.Whileσ1(ω)is?at and featureless at292K,a broad resonance develops at25K.In addition the25K spectrum shows a minimum near400cm?1similar to the SC sample. The inset shows a second channel of absorption atω?2,200 cm?1that develops at low temperatures.
FIG.4.(Right Panel)c-axis re?ectance at25K of both the SC(solid lines)and AF sample(dashed-doted line).Above 100cm?1the spectra of both samples are nearly identical. Three strong phonons are observed in the far-infrared.The left panel shows the sub-Terahertz re?ectance at25K and lower temperatures.A slight upturn is seen in the normal state spectra asω→0indicating a?nite electronic contri-bution to the conductivity.As the sample becomes super-conducting the characteristic plasma edge develops due to the screening of the superconducting carriers.(Temperatures shown:T=25,21,19,17,15,12,and7K)
FIG.5.Left Panel:low frequency R(ω)at7K and25K re-ploted on a linear scale.The straight dashed line corresponds to R(ω)calculated with only the contribution of?=17.From the location of the minimum in R(ω)and this value of?we ?ndλc=26μm as described in the text.Additionally using ?and Eq.1we?t(dashed line)R(ω)at25K withσ(ω=0) as the free variable and obtain a best?t withσ(ω=0)=1.5??1cm?1.Right Panel:electronic contribution toσ1(ω)in the SC sample below the?rst phonon.Notice the non-trivial temperature and frequency dependence above and below T c. The inset shows the peak in the loss function due to the de-velopment of the superconducting condensate.
FIG. 6.The a-axis di?erential conductivity,σSC
1
(ω)?σAF
1
(ω)plotted throughout the infrared.The oxy-gen reducing procedure leads to spectral weight transfer from the mid-infrared to lower energies.The inset shows that the total spectral weight below?14,000cm?1.
FIG.7.The in-plane scattering rate(Eq.2)for the SC (right panel)and AF(left panel)samples.Above650cm?1 in the SC sample the frequency dependence is linear.Atω<Θ1/τ(ω)is suppressed faster than a linear extrapolation of the high frequency data.This suppression can be seen at all temperatures,but is most pronounced at T c.In the super-conducting state(not shown)the spectrum is nearly the same as at T=T c.The AF sample shows a similar,but sharper threshold(arrow)also at650cm?1.These spectra should be compared to the1/τ(ω)data for hole doped materials in Fig.8
FIG.8.The in-plane scattering rate is plotted at292K, T c,and10K for under doped Bi2212(left panel)and slightly over doped Bi/Pb2212(right panel)31.In the under doped compound a gap in1/τ(ω)(marked by arrows)opens well above T c,while in the over doped compound the gap only opens in the superconducting state.Above the gap1/τ(ω) is independent of temperature for the under doped system, while it is temperature dependent at all frequencies in the over doped phase.
FIG.9.Left Panel:1/τ(ω)at T?10K for several di?er-ent families of high-T c cuprates.32,40–42All the spectra share a similar low-ωdepression with a nearly linear frequency de-pendence at higher energies.Right Panel:W(ω)derived from 1/τ(ω)using Eq.3.Again,the spectra of W(ω)all have sim-ilar form.
FIG.10.Main Panels:σ1(ω)within the CuO2plane for Bi2?x La x Sr2CuO4with x=.3(top panel)and x=.4(bot-tom panel).54A?nite frequency peak can be seen below100 cm?1in both samples for all temperatures(300K,T c,and 10K shown).The inset show the re?ectance data where clear maximum can be seen near150cm?1for both dopings.
FIG.11.Universal plot showing the correlation between σDC(T=T c)andλ?2c in layered superconductors.68,69The bottom line corresponds to the hole doped cuprates.The top line includes2D organic superconductors,transition metal dichalcogenides,granular metal?lms,and Josephson junc-tions prepared from elemental metals.Our measurements in-dicate that NCCO(star in plot)belongs to the same univer-sality class as the hole doped cuprates.
FIG.12.The normalized missing spectral weight(de-?ned in text),?K(T)/ρs(T),show the fraction of the su-per?uid density collected fromω>8?as a function of re-duced temperature.The inset shows a calculation ofσ1(ω) above and below T c for a BCS superconductor in the dirty limit.The lines at the bottom of the main panel shows how ?K(T)/ρs(T)in this model system depends on the integra-tion limit(W c)in Eq.6.Notice that with W c=8?only7% ofρs is drawn from higher energies.
0.920.940.960.981.00
7K
A.)
T = 25K
T = 292K
R (ω)
103
104
0.0
0.2
0.4
0.6
0.8
1.0
E // a SC
AF
C.)
R (ω)
100
200
300400
500
600
7000.85
0.90
0.95
1.00
B.)
T = 25K
T = 292K
R (ω)
Wave numbers (cm -1)0
100
200300400
20
40
60
80
292 K 225 K 160 K 80 K 7 K 25 K
σ1(ω) (k ?-1c m -1)
Wave numbers (cm -1)
10002000
3000
04
8
292 K
25 K
σ1(ω) (k ?-1c m -1)
Wave numbers (cm -1
)
0200400600800
123456
7825K
292K
σ1(ω) (k ?-1c m -1)
200040006000
0.0
0.51.01.52.080 K 25 K
292 K 225 K 160 K
Wave numbers (cm -1)
σ1(ω) (k ?-1c m -1)
Fig. 1
Fig. 2
Fig. 3
102
103
104
E // c
10
0.0
0.2
0.4
0.6
0.8
1.0
AF
SC
21K
19K 17K 25K
15K
12K 7K
T =
R e f l e c t a n c e
Wave numbers (cm -1)
0.3
THz
1
meV
1000
100
10
020*********
12K
7K
19K 25K
Wave numbers (cm -1)
10
15
200.0
0.2
0.4
I m (-1/ε)
25K
12K 15K 17K 19K 21K 7K
Wave numbers (cm -1)
010*********.0
0.20.4
0.6
0.8
1.0
25K
7K
Wave numbers (cm -1)
R (ω)
THz
1.5
1.2
0.9
0.60.3
1234
5
6
7
8910
σ1 (?
?1
c m -1)
02000400060008000100001200014000
-1
1
2
3
4
5
T = 292K
σ1S C (ω) - σ1A F (ω) (k ?-1c m -1)
4000800012000
0246810
SC
AF
Wave numbers (cm -1)
N e f f (106c m -2)
Fig. 4
Fig. 5
Fig. 6
0500100015000
1000
2000
3000
Θ
T = 292K 225K 160K 80K 25K
T = 292K 225K 160K 80K 25K
Antiferomagnet T N ~ 160K Wave numbers (cm -1)
1/τ(ω) (c m -1)
050010001500
2000
01000
2000
3000
Θ
Superconductor
T c = 25K
1/τ(ω) (c m -1)
0500100015000
1000
2000
3000
Θ
T = 10K
T = T c = 67K
Wave numbers (cm -1)
T = 292K
1/τ(ω) (c m -1)
050010001500
2000
01000
2000
3000
Θ
T = 10K
T = T c = 70K Over-doped Bi/Pb2212
Under-doped Bi2212
T = 292K
1/τ(ω) (c m -1)
01000
05
02000
51001000
05
02000
10
200500100015000
1000
0400800
5T c = 25 K
Nd 1.85Ce .15CuO 4+δ
T c = 36 K
La 1.86Sr .14CuO 4
T c = 94 K YBa 2Cu 3O 6.95
1/τ(ω) (c m -1)
W (ω)
T c = 88 K
Tl 2Ba 2CuO 6+δ
T c = 130 K HgBa 2Ca 2Cu 3O 8+δ
Fig. 7
Fig. 8
Fig. 9
0.0
0.2
0.4
0.6
0.8
1.0
01
2
3
W c =
8?
4?2?1?
?K (T )/ρs (T )
012345678
0.0
0.51.0ρs
W c
ω/2?
σ1(ω)/σ1(0)
10-1
100101102103104105
10-1
100
101
102
103
Conventional layered superconductors
Cuprate superconductors
NCCO
λc (μm )
σ1(T c ) (?-1cm -1)
51015
Bi 2Sr 1.7La .3CuO 4
292K
T c
10K
σ1(ω) (k ?-1c m -1)100
1000
5
10
Bi 2Sr 1.6La .4CuO 4292K
T c
10K
Wave numbers (cm -1)
σ1(ω) (k ?-1c m
-1) 0
200
400
600
800
0.80
0.850.900.95Wave numbers (cm -1)
R (ω)
200
400
600
800
0.80
0.850.900.95
Wave numbers (cm -1)
R (ω)
Fig. 10
Fig. 11
Fig. 12
XPS_Database Fe2p1/2的电子结合能： Energy (eV) Element Chemical bonding Ref 720.1Fe2p1/2 Fe° 4 720.3Fe2p1/2 Fe2B 4 720.4Fe2p1/2 FeB 4 Fe2p3/2的电子结合能： Energy (eV) Element Chemical bonding Ref 706.3Fe2p3/2 FeS2 111 706.4Fe2p3/2 Fe° 73 706.5Fe2p3/2 FeS2 150 iron 224 706.5Fe2p3/2 metallic 706.54Fe2p3/2 Fe 150 706.6Fe2p3/2 Fe2B 111 706.6Fe2p3/2FeS, tail DSJ 234 metal 13 706.6Fe2p3/2 Fe 706.7Fe2p3/2 Fe 111 706.8Fe2p3/2 FeB 111 706.8Fe2p3/2FeS2 - H2O 22j 89 706.8Fe2p3/2 Fe 183 métallique 1 706.8Fe2p3/2 Fe 706.8Fe2p3/2ds le 304 ss avec N2 implanté 218 706.8Fe2p3/2N ds l'acier 304 (bulk) 55 706.8Fe2p3/2 Fe° 156 706.8Fe2p3/2 Fe° 2 706.8Fe2p3/2Fe° in a passive film on SUS316L 65 706.9Fe2p3/2 FeP 150 706.9Fe2p3/2 Fe 89 n°1- 163 -pyrite 706.9Fe2p3/2 FeS2 n°2- 163 -pyrite 706.9Fe2p3/2 FeS2 706.9Fe2p3/2 Fe(m) 84 706.9Fe2p3/2 Fe 89 706.95Fe2p3/2FeS2 - air 11j- 89 iron 224 707Fe2p3/2 metallic 707Fe2p3/2pic XPS alliage Fe24Cr 124 707Fe2p3/2Fe metal in case of sample immersed in a 60°C solution 11 707Fe2p3/2Fe metal with a sample immersed in a room t° solution 11 707Fe2p3/2 Fe° 4 707.1Fe2p3/2FeS2 - air 3j- 89 707.1Fe2p3/2FeS2 - air 30j- 89 707.1Fe2p3/2FeS2 - air 220j - 89 métal 182 707.1Fe2p3/2 pic 707.1Fe2p3/2Fe ds 304 ss nitré 218 707.1Fe2p3/2N ds l'acier 304 (nitré) 55
XPS_Database Li的电子结合能： Energy (eV) Element Chemical bonding Ref 51.9Li1s Li métal après bombardement par l'argon 51 51.9Li1s Li metal ds DEC(LiPF6) et bomb par argon 51 53.3Li1s Li ds Li2O après bombardement par l'argon 51 53.3Li1s Li2Oap immersion ds DEC(LiPF6) et bomb par argon 51 53.6Li1s LiCO3 ou LiOH ds DEC contenant LiClO4 pdt 240 min 51 53.8Li1s Lithium carbide (formed in graphene) 71 54.6Li1s Li2CO3 pour surfaces des feuilles de Li métal 51 54.8Li1s Li 111 54.8Li1sélément naturel (liaison métallique) 147 111 54.9Li1s LiN3 150 55Li1s Li2CO3 111 55Li1s LiPO4 111 55.1Li1s LiCrO2 111 55.2Li1s LiF 150 55.5Li1s LiF 55.6Li1s Li in graphene, can't be deintercalated 71 55.6Li1s LiFaprès immersion ds DEC(LiPF6) 51 111 55.8Li1s LiCl 150 55.9Li1s LiCl 150 56.6Li1s LiBr 111 56.6Li1s LiBr 111 56.9Li1s LiCrO4 57.37Li1s Li ds Li métal 81 60.05Li1s Li ds LiC6 81 1
安规认证有以下测试项目： 1、高压测试： Dielectric Voltage withstand test高压测试为一种国际安规认证机构所要求的必测项目，产品须于出厂前座百分比的测试，它对产品而言，为品质的保证及电气安全性的指标，其测试方式是将一高于正常工作电压的异常电压加在产品上测试，并且这个电压须持续一段时间，最后判定只要无绝缘崩溃情形，即可算是通过此测试 2、绝缘阻抗测试 Insulation resistance test绝缘阻抗于相关的两点施加直流电压，最高可达1000伏特，通常使用单位为欧姆，可判定良品及不良品 3、接地阻抗测试 Ground bond test接地阻抗测试为测试产品的接地点，对产品的外壳或者金属部分，施加一个恒流电源来测试两点间的阻抗大小，一般产品规定测试25安培，阻抗不得大于0.1欧姆，而CSA则要求量测40安培检测，可检测出接地点螺丝未锁紧，接地线径太小，接地线路断路等问题 4、泄露电流测试 T ouch current test是指当设备供应电流时，流经设备金属可接触部分经人体至接地部分或可接触部分的电流。 5、输入测试： 安规输入测试目的是考察产品设计时考虑输入是否满足产品在正常工作时，输入电路是否能够承受产品工作时需要的电流。在产品标准里面规定是：最大功耗的输入电流不能大于产品标称值的110%。这个标称值也是告诉用户该产品安全工作需要的最小电流，让用户在使用这个设备前要准备这样的电气环境。 6、安全标识的稳定性测试： 对用户使用安全的警告标识，必须是稳定可靠的，不能因为使用一段时间后，变得模糊不清，而导致用户错误使用，而导致危险，或直接导致危险发生。所以需要测试这个稳定性。在安全标准里面规定是：用水测试15S，然后用汽油测试15S，标识不能模糊不清。 7、电容放电测试： 对一个电源线可以插拔的设备，其电源线经常会被拔出插座，拔出插座的电源插头，经
XPS_Database Na的电子结合能： Energy (eV) Element Chemical bonding Ref 981.4Na1s NaF 'fume particules' 25 1070.3Na1s hydroxysodalite 150 1070.5Na1s hydroxysodalite 111 1070.6Na1s Na2C2O4 150 SeO3 150 1070.6Na1s Na2 111 1070.6Na1s Na2SeO3 150 1070.7Na1s NaAsO2 MoO4 150 1070.7Na1s Na2 111 1070.7Na1s NaAsO2 1070.8Na1s NaOAc 111 1070.8Na1s Na2C2O4 111 1070.8Na1sélément naturel (liaison métallique) 147 1070.8Na1s metal 159 150 H2PO2 1070.9Na1s Na PO4 150 1070.9Na1s Na3 TeO4 150 1070.9Na1s Na2 1070.9Na1s Na2 SnO3, 3 H2O 150 150 1070.9Na1s NaOOCH 1070.9Na1s NaOAc 150 1070.9Na1s NaMoO4 111 150 S2O4 1071Na1s Na2 SO4 150 1071Na1s Na2 1071Na1s Na2 CrO4 150 thioglycollate 150 1071Na1s Na 150 1071Na1s NaF 1071.1Na1s Na2 WO4 150 150 1071.1Na1s Na BiO3 benzene-sulphonate 150 1071.1Na1s Na 111 1071.1Na1s Na2S2O4 111 1071.1Na1s Na2SO4 111 1071.1Na1s NaF 111 1071.1Na1s NaTeO4 1071.1Na1s Na2SnO3.H2O 111 111 1071.1Na1s Na3PO4 1071.1Na1s NaOAc 111 111 1071.1Na1s NaOOCH 1071.2Na1s NaNO3 150 1071.2Na1s Na2 SO3 150 111 1071.2Na1s Na2CrO4 thioglycollate 111 1071.2Na1s Na 1071.2Na1s NaH2PO2 111 150 1071.3Na1s Na2CO3
对“结合能”的几点辨析 湖北省恩施高中 陈恩谱 结合能的概念，是《原子核》一章的一个教学难点，学生普遍错误的将“结合能”理解成原子核具有的能量——以为原子核的比结合能大，就是平均每个核子具有的能量越大；另一方面，在理解核能释放的过程时，无法从结合能的角度理清思路——他们不知道把自由核子作为分析问题的等效中间状态，因此必然无法将结合能与核能释放联系起来；而课本在介绍比结合能时，也没能够将核子平均质量曲线做一个介绍，从而对理解能力较差的学生提出了较高的要求，使他们始终不得其门而入。为了解决这些问题，笔者结合多年的教学探索，特在此对相关问题作一辨析，期与同行交流，望各位批评指正。 一、结合能的概念 1、结合能的定义 结合角度定义：自由核子结合成原子核的过程中释放出来的能量，叫做该原子核的结合能。 分解角度定义：将原子核分解成自由核子时所需要的最小的能量，叫做该原子核的结合能。 由能量守恒可知，上述两个定义是一致的。注意，大于结合能的能量，当然可以将原子核分解成自由核子。 2、类比化学键键能理解结合能 一个化学键的键能，比如H-H 共价键的键能，是指两个自由的氢原子形成H-H 共价键时释放出来的能量，也就是将H-H 共价键拆开时所需要的最小的能量。这和原子核的结合能概念是一样的，因此，我们可以将化学键键能称之为化学键的结合能，而原子核的结合能，也可以称之为核键键能。 3、一个结论 一个原子核的基础上，再结合一些核子，从而形成更大的原子核时，将进一步释放能量，因此，原子核越大，其结合能（也就是结合过程中释放出来能量）更越大。 二、比结合能的概念 1、定义：原子核的结合能与原子核内核子数的比值，叫做比结合能，也叫作平均结合能。通俗一点儿理解，就是在结合成原子核的过程中，平均每个核子释放出来的能量。 2、比结合能曲线与平均核子质量曲线 （1）比结合能曲线 不同的原子核，其比结合能不一样。右图为不同原子核的比结合能随 原子序数变化的大致曲线，其中，56 26Fe 原子核的比结合能最大。 （2）平均核子质量曲线 比结合能，就是平均每个核子释放出来的能量，释放出来的越多，平 均每个核子剩下的能量就越少，由2E mc 可知，平均每个核子的质量也 就越小，如右图所示，其中，56 26Fe 原子核的平均核子质量最小。 3、一个结论 比结合能越大，意味着拆开每个核子所需要能量更多，拆开原子核更 困难，因此，原子核的比结合能越大，原子核越稳定。由前述两个曲线可 以看出，5626Fe 原子核在所有原子核中是最稳定的。 注意，并不是原子核的结合能越大越稳定，而是比结合能越大，原子核越稳定；原子核太大时，原子核的结合能尽管很大，但原子核却会变得很不稳定，很容易发生衰变。 三、核能的释放 1、从平均核子质量角度看核能释放 释放能量，意味着释放质量，因此，释放能量的核反应，整个体系的质量会减小，即存在质量亏损，但是总的核子数并不变化（质量数守恒），E Z m Z m Z
安规及安规认证申请流程简介 一.安规简介 1.定义 为了保证人身安全,财产,环境等不受伤害和损失,所做出的规定. 2.安规所涉及的要求: a.电击 b.火灾 c.电磁辐射 d.环境污染 e.化学辐射 f.能量冲击 g.化学腐蚀 h.机械伤害和热伤害 3.世界主要安规体系 a.I E C体系----以欧盟为代表 b.U L体系----以美国为代表 尽管这两个体系各自独立,但现在有互相承认,走向一致的趋势. 4.安规认证 安规认证其实是一种技术壁垒,世界各国为了限制别国的产品进入本国,都对安规有不同要求,而且是带有强制性
的. 常见的安规认证 a.U L-美国 b.T U V,V D E,G S-德国 c.C C C-中国 d.P S E-日本 e.C E-欧盟 f.K E T I-韩国 g.--丹麦 h.--挪威 i.--芬兰 j.--瑞典 另外,还有澳大利亚,新西兰,新加坡等国. 二.安规认证的申请流程 1.向安规机构递交申请资料. 2.安规认证机构会在承诺的时间内给予是否接受申请的答覆. 3.安规机构接受申请後,申请人开始送样接受安规测试. 4.如果样品通过安规测试,安规认证机构安排工厂检查(U L叫I P I),如果未通过测试,则退回申请人,申请人对未通过测试的项目进行改善,然後再重新送样测试,如果第
二次未通过,则需要重新申请. 5.工厂检查通过,安规认证机构颁发认证证书或安规标志 使用授权书,申请人可以在获得认证的产品使用认证机构 的标志. 如果工厂检查未通过,认证机构会给申请人一段时间进行 整改,整改结束後进行复查,复查若未通过,则须重新申请. 6.以後认证机构对获得认证的产品转入跟踪检查,U L一般是一年四次,C C C是每年一次,其他认证机构的周期也大都为1年1次.跟踪检查主要检查产品的一致性,但象 C C C,T U V等还对品质系统进行审查. 三.电子产品的安规基本要求 1.耐压(抗电强度)-防止电击伤害 2.绝缘电阻-防止电击伤害 3.接地电阻-防止电击伤害 4泄漏电流-防止电击伤害 5.电磁兼容-抗电磁干扰能力和对其他电子产品的影响 6.耐火阻然-防止火灾危险 7.机械结构-防止机械结构缺陷引起的损伤,灼伤等. 8.能源冲击-防止因为大电流引起火灾或电弧灼伤 四.电子产品在制程中的安规要求
XPS_Database Zn的电子结合能： Energy (eV) Element Chemical bonding Ref 1045Zn2p1/2Cu Zn alpha, béta 178 178 1045.1Zn2p1/2 ZnO 1045.9Zn2p1/2 ZnI2 62 1046.2Zn2p1/2 ZnCl2 62 1046.4Zn2p1/2 ZnBr2 62 Zn的电子结合能： Energy (eV) Element Chemical bonding Ref 88.4Zn2p3/2Cu Zn alpha, béta 178 1020.7Zn2p3/2 ZnP2 150 1021.2Zn2p3/2 Zn 111 1021.4Zn2p3/2 ZnTe 150 1021.4Zn2p3/2 ZnS 150 acethylacetonate 111 1021.4Zn2p3/2 Zn 1021.4Zn2p3/2 ZnO 157 1021.5Zn2p3/2 ZnAl2O4 150 1021.6Zn2p3/2 ZnF2 150 1021.6Zn2p3/2 ZnO 111 1021.6Zn2p3/2 ZnTe 111 1021.6Zn2p3/2ZnO ds P2O5 ZnO/P2O5 = 1.2 molar 252 1021.6Zn2p3/2 Zn(Met)2 235 1021.62Zn2p3/2 Zn 150 1021.8Zn2p3/2 ZnSe 150 1021.9Zn2p3/2 ZnO 150 1021.9Zn2p3/2 ZnS 111 1021.9Zn2p3/2 Zn 111 1021.9Zn2p3/2hemimorphite (Zn silicate) 111 1022Zn2p3/2 ZnSe 111 1022Zn2p3/2Cu Zn alpha, béta 178 1022Zn2p3/2élément naturel (liaison métallique) 147 1022.1Zn2p3/2 ZnO 178 1022.2Zn2p3/2 ZnF2 111 1022.2Zn2p3/2 ZnO 111 1022.2Zn2p3/2ZnO ds P2O5 ZnO/P2O5 = 0.4 molar 252 1022.3Zn2p3/2 ZnI2 150 1022.3Zn2p3/2ZnO ds P2O5 ZnO/P2O5 = 1 molar 252 1022.4Zn2p3/2ZnO ds P2O5 ZnO/P2O5 = 1,5 molar 252 1022.4Zn2p3/2ZnO ds P2O5 ZnO/P2O5 = 2 molar 252 1022.8Zn2p3/2 ZnSO4 150 1022.8Zn2p3/2 ZnI2 111 1023Zn2p3/2 ZnBr2 111 1023Zn2p3/2 ZnCl2 62
安全距离要求 所谓安全距离，就是为保护人在使用电子产品的时候，危险电压带电部分与人不能轻易接触到，也不能让它来引起危险导致威胁人身安全。 因此必须在一般情况下，安全距离是在产品设计中最重要的部分之一。检查安全距离从设计阶段开始。结构检查人员会首先检查PCB板上的安全距离（最好拿空的PCB板用透明薄尺或游标卡尺来测量），之后，就是检查危险电压带电部分与其它部分（如外壳、安全电压 部分等）距离等等。总之，一切关乎与安全的部分都要测量，特别重点会在电源部分。 具体参考各种安全标准： IEC60950\ IEC60065\UL60950\GB8898\GB4943等 以下引自其他文章： 安全距离包括电气间隙（空间距离），爬电距离（沿面距离）和绝缘穿透距离 1、电气间隙：两相邻导体或一个导体与相邻电机壳表面的沿空气测量的最短距离。 2、爬电距离：两相邻导体或一个导体与相邻电机壳表面的沿绝绝缘表面测量的最短距离。 电气间隙的决定： 根据测量的工作电压及绝缘等级，即可决定距离 一次侧线路之电气间隙尺寸要求，见表3及表4 二次侧线路之电气间隙尺寸要求见表5 但通常：一次侧交流部分：保险丝前L―N≥2.5mm，L.N PE（大地）≥2.5mm，保险丝 装置之后可不做要求，但尽可能保持一定距离以避免发生短路损坏电源。 一次侧交流对直流部分≥2.0mm 一次侧直流地对大地≥2.5mm （一次侧浮接地对大地） 一次侧部分对二次侧部分≥4.0mm，跨接于一二次侧之间之元器件 二次侧部分之电隙间隙≥0.5mm即可 二次侧地对大地≥1.0mm即可 附注：决定是否符合要求前，内部零件应先施于10N力，外壳施以30N力，以减少其距离，使确认为最糟情况下，空间距离仍符合规定。 爬电距离的决定： 根据工作电压及绝缘等级，查表6可决定其爬电距离 但通常：（1）、一次侧交流部分：保险丝前L―N≥2.5mm，L.N 大地≥2.5mm，保险丝 之后可不做要求，但尽量保持一定距离以避免短路损坏电源。 （2）、一次侧交流对直流部分≥2.0mm （3）、一次侧直流地对地≥4.0mm如一次侧地对大地 （4）、一次侧对二次侧≥6.4mm，如光耦、Y电容等元器零件脚间距≤6.4mm要开 槽。 （5）、二次侧部分之间≥0.5mm即可 （6）、二次侧地对大地≥2.0mm以上 （7）、变压器两级间≥8.0mm以上 3、绝缘穿透距离： 应根据工作电压和绝缘应用场合符合下列规定：
1.0Bi6p1 3.9 Pt 5d10.0P 3p 18.0At 6s 24.0Kr 4s 34.0K 3s 44.0Ra 6s 5 2.0Tm 5s 65.7V 3s 1.0Ce4f 4.0 Ir 5d10.0Ti 4s 18.0Ce 5p 24.0Sn 4d 35.0Re 5p3 44.0U 6s 5 2.3Yb 5s 66.0Ni 3p 1.0Co3d 4.0Pm 4f 10.0V 4s 18.0Pr 5p 25.0Th 6p1 35.2Mo 4p 44.4Y 4s 5 2.6Fe 3p 66.0Pt 5p1 1.0Cr3d 4.5Ag 4d10.0Zr 5s 18.1Hf Ntv Ox 26.0Bi 5d3 35.2W Na2WO445.0Ta 5p1 5 3.0Sn loss 67.8Ta 5s 1.0Fe3d 4.8Dy 5d10.5Bi 6s 18.2 C 2s 26.0He 1s 35.3Y loss 45.1As 2O3 53.4Os 4f5 68.0Ra 5d 1.0Ga4p 5.0 B 2p10.7Cd 4d5 18.4Sr 4p 26.0Rn 6s 35.8W O3 45.5As Ntv Ox54.0Os 5p1 68.0Tc 4s 1.0Hf5d 5.0 Br 4p11.0Kr 4p 18.7Ga 3d5 26.1Lu 5p 36.0Ce 5s 45.7Ge loss 54.2Se CdSe68.5Br 3d5 1.0In 5p 5.0Ca 3d11.0Rn 6p 18.8Ga 3d 26.8Ta 2O5 36.0Gd 5s 46.0Re 5p1 54.5Se GeSe68.5Br KBr 1.0Na3s 5.0 Er 4f 11.0Sc 4s 18.9Ga 3d3 26.8Zr 4p 36.6Sr 4s 46.3Ga loss 54.9Se 3d5 68.8Cd 4p 1.0Os5d 5.0Po 6p11.1Cs 5p3 19.0Eu 5p 27.0Br 4s 36.7V 3p 46.8Re 2O7 54.9Li 1s 69.0Br 3d 1.0Pb6p 5.3Se 4p11.6Cd 4d3 19.0Nd 5p 28.2Sc 3p 37.0W 5p3 46.8W 5p1 54.9Li OH 69.5Br 3d3 1.0Sn5p 5.5 Cl 3p1 2.0Cs 5p 19.0Pb 5d5 28.6In loss 37.5Hf 5p1 47.0Mn 3p 54.9Se 3d 70.0Re loss 1.2Yb4f7 5.8Au 5d12.0Po 6s 19.0Ra 6p 28.8Rb 4s 38.0Pm 5s 47.0Rh 4p 55.2Se GeSe271.0Pt 4f7 1.4Pd4d 6.0Ta 5d12.0Te 5s 19.0Sm 5p 29.0Dy 5p1 38.0Pr 5s 47.9Ru 4p 55.3Li CO3 71.8Mg loss 1.4Rh4d 6.0 Y 4d1 2.0Tl 5d5 19.1Ga Sb fract29.0Er 5p 38.3Sn loss 48.0Dy 5s 55.6Nb 4s 72.6Pt 4f 2.0Cd5p 6.2Hg 5d12.6Cs 5p1 19.4Ga AlAs etch29.0Lu 5p 39.0Eu 5s 48.0Rn 5d 55.7Se 3d3 72.7Al 2p3 2.0Mg3s 6.9Eu 4f 1 3.0Tl 5d 19.5N 2s 29.1Ge 3d5 39.0Nd 5s 48.0Sb loss 56.8Au 5p3 72.9Al 2p 2.0Mo4d 7.0 O 2p1 3.2Rb 4p 19.7Ga P fract 29.2 F 2s 39.0Tc 4p 48.5 I 4d 56.8Lu 5s 73.1Tl 5p3 2.0Nb4d 7.0Sm 4f 13.2Rb 4p 19.7Ga As fract29.4Ge 3d 39.5Tm 5p 49.5Ho 5s 57.4Er 5s 73.2Al 2p1 2.0Nd4f 7.0Sn 5s1 4.0Ne 2p 20.0U 6p 29.5Ho 5p1 40.0At 5d 49.5Mg CO3 58.0Ag 4p 73.8Al N 2.0Ni 3d 7.0Xe 5p14.0Sc 3d 20.2Zn loss 29.7Ge 3d3 40.0Ba 5s 49.6Mg(OH)258.0Fr 5d 74.0Au 5p1 2.0Pr 4f 7.1Lu4f714.2Hf 4f7 20.5Gd 5p 30.2Ge Se 40.0In loss 49.6Mg 2p3 58.0Hg 5p3 74.2Cr 3s 2.0Sb5p 7.1Tb 4f 15.0Fr 6p 20.7Ga 2O3 30.3Na 2p 40.0Tb 5s 49.7Mg O 58.1W loss 74.3Al 2O3 2.0Sc4p 7.7Gd 4f 15.0H 1s 21.0Pb 5d3 30.9Nb 4p 40.1Te 4d 49.8Mg 2p 58.2Ti 3s 74.3Al2O3-nH2O 2.0Tc4d 7.8Dy 4f 15.0Hf 4f 21.6Ta 4f7 30.9Pb loss 40.2Re 4f7 49.9Mg 2p1 58.3Te loss 74.4Pt 4f5 2.0Ti 3d 8.0 At 6p15.0Rb 4p1 21.8Tb 5p 31.0Hf 5p3 41.0Ne 2s 50.0Mg CO3 58.6Ag 4p 74.4Al (OH)3 2.0V 3d 8.0 S 3p15.0Tl 5d3 22.0Dy 5p3 31.0Po 5d 41.0Sm 5s 50.0Sr loss 58.9Y loss 74.9Cu 3p 2.0Yb 4f 8.3Ho 4f 15.7Cl 3s 22.0Pm 5p 31.3W 4f7 41.2Re 4f 50.3Zr 4s 59.0Co 3p 74.9Se loss 2.0Zr 4d 8.3Lu 5d15.9Hf 4f5 22.3Ar 3s 31.5Ge Se2 41.4Re Ntv Ox 50.4Mg NtvOx159.2As loss 75.0Cs 4d5 2.5Yb4f58.4Lu2O315.9 I 5s 22.7Ta 4f 31.7Sb 4d 41.5As 3d5 50.7Os 4f7 60.8Ir 4f7 75.1Pt O2-nH2O 2.6Te5p 8.5Tm4f716.0K 3p 2 3.0Cs 5s 32.1Ga loss 41.8As 3d 50.7Pd 4p 61.0Mg loss 75.1W 5s 2.8Cu3d 8.6Lu4f516.0P 3s 2 3.1O 2s 32.3W 4f 42.0As S 50.7Sc 3s 62.0Ir 4f 75.5Al Ntv Ox 2.8Mn3d 8.9 Ar 3p16.0S 3s 23.3Ho 5p3 32.4Ti 3p 42.0Th 6s 50.9Mg reoxid62.0Ir O2 76.0Cs 4d 2.8Re5d 9.0 F 2p16.9In 4d 2 3.3Y 4p 32.6Ta 5p3 42.1Ca 3s 51.0Ir 5p3 62.0Ir 5p1 77.8Ni loss 2.8Si 3p 9.0Ru 4d17.0La 5p 23.4Ta S2 33.0La 5s 42.1Cr 3p 51.0Mg NtvOx262.0Mo 4s 78.3In 4p 2.8W 5d 9.0Sb 5s17.0Th 6p3 2 3.5Ca 3p 33.2Ge O2 42.2As 3d3 51.4Os 4f 62.0Xe 4d 79.0Cs 4d3 3.0Ge4p 9.0 Si 3s17.0Xe 5s 23.5Yb 5p 33.4Lu 5p 42.7Re 4f5 51.5Pt 5p3 62.3Hf 5s 80.0Ru 4s 3.0 I 5p 9.1As 4p17.1Hf O2 23.8Bi 5d 33.5W 4f5 42.7Ta loss 51.5Mg reoxid62.7Ir Ntv Ox80.7Rh 4s 3.0Pb6s 9.7Zn 3d17.7Pb 5d 2 4.0Ta 4f5 33.8Ge Ntv Ox43.0As 2S3 51.7Re loss 63.3Na 2s 81.0Hg 5p1 3.2Bi6p310.0Ba 5p17.9Ga InAs (ar)24.0Bi 5d5 34.0Fr 6s 44.0Os 5p3 51.9Mg NtvOx363.8Ir 4f5 81.8Re 5s
XPS_Database Ni的电子结合能： Energy (eV) Element Chemical bonding Ref 215 869.6Ni2p1/2 Ni Ni的电子结合能： Energy (eV) Element Chemical bonding Ref 851.4Ni2p3/2ds le 304 ss avec N2 implanté 218 851.4Ni2p3/2 Ni11 218 851.95Ni2p3/2 AuNi 150 852Ni2p3/2Ni (16 min)/Al2O3/Al 229 852.1Ni2p3/2 Ni 111 métallique 118 852.3Ni2p3/2 Ni 852.4Ni2p3/2 Ni 215 852.48Ni2p3/2 Ni 150 852.5Ni2p3/2 Ni 247 852.5Ni2p3/2Ni métal ( 10puis-6 torr) 78 852.5Ni2p3/2Ni métal ( 250°C -1h ) 78 852.5Ni2p3/2Ni, Ni foil polishing and Ar+ etching 101 852.6Ni2p3/2 NiS 150 852.6Ni2p3/2Ni, Ni foil polish and Ar+ etching, + O2 at 200°C/1h 101 852.6Ni2p3/2Ni, Ni foil polishing + water immersion/28h 101 Ni 229 852.7Ni2p3/2 bulk metal 13 852.7Ni2p3/2 Ni 852.8Ni2p3/2 Ni2Si 150 852.8Ni2p3/2 Ni-21Cr-8Fe 183 852.8Ni2p3/2 Ni 183 852.8Ni2p3/2Ni° in a passive film on SUS316L 65 852.9Ni2p3/2 Ni2P 150 852.9Ni2p3/2 2 min Ni deposit : Ni dispersed on Al2O3 229 852.9Ni2p3/2Ni, Ni foil polishing and Ar+ etching+H2S 400°C/1h 101 853Ni2p3/2 NiB 150 853Ni2p3/2Ni (7 min)/Al2O3/Al annealed to 800K for 30 min 229 853Ni2p3/2Ni metal with a sample immersed in a 60°C solution 11 853Ni2p3/2Ni metal with a sample immersed in a room t° solution 11 853Ni2p3/2NiS/Ni3S2 -Ni foil polish in H2O/28h+H2S 400°C/1h 101 853Ni2p3/2Ni Polish +Ar+,+O2 -200°C/1h+400°C/2h30mn+H2S 400°C/1h 101 853.1Ni2p3/2NiOads ( 10puis-6 torr) 78 853.1Ni2p3/2NiOads ( air 15min ) 78 853.3Ni2p3/2élément naturel (liaison métallique) 147 853.5Ni2p3/2 NiO 111 853.55Ni2p3/2 Al3Ni 150 853.6Ni2p3/2 NiI2 111 853.9Ni2p3/2 Ni(C5H5)2 111 853.9Ni2p3/2 Ni(PPh3)2 111
对一个电源线可以插拔的设备， 其电源线经常会被拔出插座， 拔出插座的电源插头， 经 安规认证有以下测试项目: 1、高压测试: Dielectric Voltage withsta nd test 高压测试为一种国际安规认证机构所要求的必测项目，产品须于出厂前座百分比的测 试，它对产品而 言，为品质的保证及电气安全性的指标, 其测试方式是将一高于正常工作电 压的异常电压加在产品上测试， 并且这个电压须持续一段时间， 最后判定只要无绝缘崩溃情 形，即可算是通过此测试 2、绝缘阻抗测试 In sulatio n resista nee test 绝缘阻抗于相关的两点施加直流电压，最高可达 判定良品及不良品 3、接地阻抗测试 Ground bond test 接地阻抗测试为测试产品的接地点， 对产品的外壳或者金属部分， 施加一个恒流电源来 测试两点间的阻抗大小，一般产品规定测试 25安培，阻抗不得大于 0.1欧姆，而CSA 则 要求量测40安培检测，可检测出接地点螺丝未锁紧，接地线径太小，接地线路断路等问题 — 4、泄露电流测试 Touch current test 是指当设备供应电流时，流经设备金属可接触部分经人体至接地部 分或可接触 部分的电流。- 5、输入测试: 输入电路是 否能够 承受产品工作时需要的电 流。 在产品标准里面规定是：最大功耗的输入电流不能大于 产品标称值的110%。这个标称值也是告诉用户该产品安全工作需要的最小电流，让用户在 使用这个设备前要准备这样的电气环境。 6、安全标识的稳定性测试: 对用户使用安全的警告标识， 必须是稳定可靠的，不能因为使用一段时间后， 变得模糊 不清，而导致用户错误使用，而导致危险，或直接导致危险发生。所以需要测试这个稳定性。 在安全标准里面规定是：用水测试 15S ，然后用汽油测试 15S ，标识不能模糊不清。~ 1000伏特，通常使用单位为欧姆，可 安规输入测试目的是考察产品设计时考虑输入是否满足产品在正常工作时,
XPS_Database S的电子结合能： Energy (eV) Element Chemical bonding Ref 2478.5S1s H2S 243 243 2483.7S1s SO2 243 2490.1S1s SF6 S的电子结合能： Energy (eV) Element Chemical bonding Ref 161.5S2p NiS, Ni foil polishing and Ar+ etching+H2S 400°C/1h 101 161.6S2p NiS, Ni foil polishing + in H2O/28h+H2S 400°C/1h 101 161.6S2p NiS, Ni foil Polish+Ar+,O2 oxydations/T°C+H2S 400°C/1h 101 161.8S2p(S)2- in Co foil polish- Ar+ etch, +H2S -400°C/2h 101 162.9S2p(S2)2- or SH -Co foil polish- Ar+ etch, +H2S -400°C/2h 101 163S2p(S2)2-, Ni Polish +Ar+O2 oxydations/T°C+H2S 400°C/1h 101 163.1S2p(S2)2-, Ni foil polishing and Ar+ etching+H2S 400°C/1h 101 163.1S2p(S2)2-, Ni foil polish+ in H2o/28h+H2S 400°C/1h 101 S的电子结合能： Energy (eV) Element Chemical bonding Ref 107.3S2p3/2 PbS 89 160S2p3/2 sulphides 186 -air3'- 89 160.3S2p3/2 PbS 160.5S2p3/2 PbS 111 160.55S2p3/2PbS - H2O 19j- 89 160.55S2p3/2 PbS 89 160.7S2p3/2 p-NaSC6H4NO2 111 160.7S2p3/2vieillissement à l'air de la galène pdt 3mn 89 160.9S2p3/2PbS -air 220j- 89 160.95S2p3/2vieillissement à l'eau de la galène pdt 19j 89 161S2p3/2 FeS 111 161.2S2p3/2 KFeS2 111 161.2S2p3/2RSNa ou RSK 245 161.2S2p3/2 S(2-) monosulfide 234 3'- 89 -air 161.25S2p3/2 CuFeS2 161.3S2p3/2 CuFeS2 89 161.3S2p3/2vieillissement à l'air de la galène pdt 220j 89 161.4S2p3/2 Na2SSO3 111 161.4S2p3/2 Ni(SPh)2(dppe) 235 161.5S2p3/2 ZnS 150 161.5S2p3/2 Na2S 111 161.5S2p3/2 CuFeS2 3j- 89 -air 161.5S2p3/2S (ads) / Mo(110) - S strongly bound 103 161.6S2p3/2CuFeS2 - H2O 22j- 89 161.6S2p3/2 Mo(NO)(S2CN(C2H5)2)3 235
XPS_Database Co2p3/2的电子结合能 Energy (eV) Element Chemical bonding Ref 777.7Co2p3/2 CoB 111 777.8Co2p3/2 Co 111 777.9Co2p3/2 CoS2 150 777.9Co2p3/2Co -Co foil polishing and Ar+ etching 101 métal 247 778Co2p3/2 Co 778Co2p3/2Co-Sx, Co foil polishing +in H2O/63h+H2S -400°C/2h 101 778.1Co2p3/2 Co2B 111 778.1Co2p3/2Co-Sx, foil ecth+O2-200°C/30mn+400°C/30mn+H2S-400°C/2h 101 778.12Co2p3/2 Co 150 778.2Co2p3/2 CoP 150 778.2Co2p3/2Co° in Co-Cr alloy 65 778.2Co2p3/2Co foil polish- Ar+ etch, +H2S -400°C/2h 101 metal 13 778.2Co2p3/2 Co 778.5Co2p3/2 CoSe 150 778.8Co2p3/2 Co(C5H5))2 111 779.2Co2p3/2 Co2O3 111 779.2Co2p3/2 CoFe2O4 111 dibuthyldithiocarbamate 111 779.5Co2p3/2 Co 779.6Co2p3/2 CoOOH 111 779.8Co2p3/2 Co3O4 111 779.8Co2p3/2 CoMn2O4 111 779.9Co2p3/2 Co(salen) 111 779.9Co2p3/2 CoCr2O4 111 779.9Co2p3/2 Co2O3 247 779.9Co2p3/2 CoFe2O4 247 780Co2p3/2 CoO 111 780Co2p3/2 ZnCo2O4 111 780Co2p3/2 Co(N4-(CH3)4ethylenediamide)(NO3)2 111 780Co2p3/2 CoO 247 780Co2p3/2 CoOOH 247 780.1Co2p3/2 CoOOH 150 780.1Co2p3/2 Co(OH)2 111 780.1Co2p3/2 Co3O4 157 780.1Co2p3/2 CoO 13 780.2Co2p3/2 CoO 150 780.2Co2p3/2 Co(CO)3NO 111 780.2Co2p3/2 CoO 157 780.2Co2p3/2 Co(Met)2 235 780.3Co2p3/2 CoAl2O4 111 780.3Co2p3/2 Co3O4 155 780.3Co2p3/2Co-Ox -Co foil polishing + water immersion/24h 101 780.4Co2p3/2Co foil polish- Ar+ etch, +O2 -200°C/30 mn+400°C/30mn 101
电子产品的安全距离及其相关安全要求 Document number【AA80KGB-AA98YT-AAT8CB-2A6UT-A18GG】
话题：电子产品的安全距离及其相关安全要求所谓安全距离，就是为保护人在使用电子产品的时候，危险电压带电部分与人不能轻易接 触到，也不能让它来引起危险导致威胁人身安全。 因此必须在一般情况下，安全距离是在产品设计中最重要的部分之一。检查安全距离从设 计阶段开始。结构检查人员会首先检查PCB板上的安全距离（最好拿空的PCB板用透明薄尺 或游标卡尺来测量），之后，就是检查危险电压带电部分与其它部分（如外壳、安全电压 部分等）距离等等。总之，一切关乎与安全的部分都要测量，特别重点会在电源部分。 具体参考各种安全标准： IEC60950\ IEC60065\UL60950\GB8898\GB4943等 以下引自其他文章： 安全距离包括电气间隙（空间距离），爬电距离（沿面距离）和绝缘穿透距离 1、电气间隙：两相邻导体或一个导体与相邻电机壳表面的沿空气测量的最短距离。 2、爬电距离：两相邻导体或一个导体与相邻电机壳表面的沿绝绝缘表面测量的最短距离。 电气间隙的决定： 根据测量的工作电压及绝缘等级，即可决定距离 一次侧线路之电气间隙尺寸要求，见表3及表4 二次侧线路之电气间隙尺寸要求见表5 但通常：一次侧交流部分：保险丝前L—N≥2.5mm，L.N PE（大地）≥2.5mm，保险丝 装置之后可不做要求，但尽可能保持一定距离以避免发生短路损坏电源。 一次侧交流对直流部分≥2.0mm 一次侧直流地对大地≥2.5mm （一次侧浮接地对大地） 一次侧部分对二次侧部分≥4.0mm，跨接于一二次侧之间之元器件 二次侧部分之电隙间隙≥0.5mm即可 二次侧地对大地≥1.0mm即可 附注：决定是否符合要求前，内部零件应先施于10N力，外壳施以30N力，以减少其距离， 使确认为最糟情况下，空间距离仍符合规定。 爬电距离的决定： 根据工作电压及绝缘等级，查表6可决定其爬电距离 但通常：（1）、一次侧交流部分：保险丝前L—N≥2.5mm，L.N?大地≥2.5mm，保险丝 之后可不做要求，但尽量保持一定距离以避免短路损坏电源。 （2）、一次侧交流对直流部分≥2.0mm （3）、一次侧直流地对地≥4.0mm如一次侧地对大地 （4）、一次侧对二次侧≥6.4mm，如光耦、Y电容等元器零件脚间距≤6.4mm要开 槽。 （5）、二次侧部分之间≥0.5mm即可 （6）、二次侧地对大地≥2.0mm以上 （7）、变压器两级间≥8.0mm以上 3、绝缘穿透距离：