Electrical and structural properties of MgB2 films prepared by sequential deposition of B a

Ferroelectric and piezoelectric properties of tungsten substituted SrBi 2Ta 2O 9ferroelectric ceramicsIndrani Coondoo *,S.K.Agarwal a ,A.K.Jha ba Superconductivity and Cryogenics Division,National Physical Laboratory,Dr K.S.Krishnan Road,New Delhi 110012,India bDepartment of Applied Physics,Delhi College of Engineering,Bawana Road,Delhi 110042,India1.IntroductionDefects in crystals significantly influence physical and various other properties of materials [1].For instance,as it is well known,doping by other elements leads to significant changes in the electrical properties of silicon.Historically,‘‘defect engineering’’has been developed in the field of semiconducting materials such as compound semiconductors as well as in diamond,Si and Ge [2–4].Subsequently,the concept of defect engineering has been applied to other functional materials,and the significant improve-ment in material properties have been achieved in high transition-temperature superconductors [5],amorphous SiO 2[6],photonic crystals [7]and also in the field of ferroelectrics,such as BaTiO 3,Pb(Ti,Zr)O 3(PZT),etc.[8,9].Various structural and electrical properties of bismuth layer-structured ferroelectrics (BLSF)are also strongly affected on deviation from stoichiometric composi-tions and defects have been recognized as a crucially important factor [10–13].It has been found that in BLSF small changes in chemical composition result in significantly altered dielectric and ferroelectric properties including dielectric constant and remanent polarization.In SrBi 2Ta 2O 9(SBT)and SrBi 2Nb 2O 9(SBN),orthor-hombic structural distortions with non-centrosymmetric spacegroup A 21am cause spontaneous ferroelectric polarization (P s )along a axis [14,15].SBT,a member of the BLSF family,has occupied an important position among the Pb-free ferroelectric memory materials [16–18].Tungsten (W 6+)has recently been investigated as a dopant for bismuth titanates and lanthanum doped bismuth titanates,in which the remanent polarization was observed to enhance when a small amount of Ti 4+was substituted by W 6+[19,20].With the objective to improve structural,dielectric and ferroelectric proper-ties,the hexavalent tungsten (W 6+)was chosen as a donor cation for partial replacement of the pentavalent tantalum (Ta 5+)SBT.In this report,the effect of tungsten substitution in SBT (SBTW),on the microstructural,ferroelectric and piezoelectric properties is reported.The results including the improvement in polarization properties have been discussed.2.ExperimentalSamples of compositions SrBi 2(W x Ta 1Àx )2O 9(SBWT),with x =0.0,0.025,0.050,0.075,0.10and 0.20were synthesized by solid-state reaction method taking SrCO 3,Bi 2O 3,Ta 2O 5and WO 3(all from Aldrich)in their stoichiometric proportions.The powder mixtures were thoroughly ground and passed through sieve of appropriate size and then calcined at 9008C in air for 2h.The calcined mixtures were ground and admixed with about 1–1.5wt%polyvinyl alcohol (Aldrich)as a binder and then pressed at $300MPa into disk shaped pellets.The pellets were sintered at 12008C for 2h in air.Materials Research Bulletin 44(2009)1288–1292A R T I C L E I N F O Article history:Received 3October 2008Received in revised form 5December 2008Accepted 6January 2009Available online 15January 2009Keywords:A.CeramicsC.X-ray diffractionD.FerroelectricityA B S T R A C TTungsten substituted samples of compositions SrBi 2(W x Ta 1Àx )2O 9(x =0.0,0.025,0.050,0.075,0.10and 0.20)were synthesized by solid-state reaction method and studied for their microstructural,electrical conductivity,ferroelectric and piezoelectric properties.The X-ray diffractograms confirm the formation of single phase layered perovskite structure in the samples with x up to 0.05.The temperaturedependence of dc conductivity vis-a`-vis tungsten content shows a decrease in conductivity,which is attributed to the suppression of oxygen vacancies.The ferroelectric and piezoelectric studies of the W-substituted SBT ceramics show that the remanent polarization and d 33values increases with increasing concentration of tungsten up to x 0.05.Such compositions with low conductivity and high P r values should be excellent materials for highly stable ferroelectric memory devices.ß2009Elsevier Ltd.All rights reserved.*Corresponding author.Present address:Liquid Crystal Group,National Physical Laboratory,Dr K.S.Krishnan Road,New Delhi 110012,India.Tel.:+919810361727;fax:+911125170387.E-mail address:indrani_coondoo@ (I.Coondoo).Contents lists available at ScienceDirectMaterials Research Bulletinj o ur n a l h o m e p a g e :w w w.e l se v i e r.c om /l oc a t e /m a t r e sb u0025-5408/$–see front matter ß2009Elsevier Ltd.All rights reserved.doi:10.1016/j.materresbull.2009.01.001X-ray diffractograms of the sintered samples were recorded using a Bruker diffractometer in the range 108 2u 708with CuK a radiation.The sintered pellets were polished to a thickness of 1mm and coated with silver paste on both sides for use as electrodes and cured at 5508C for half an hour.Electrical conductivity was performed using Keithley’s 6517A Electrometer.The polarization–electric field (P –E )hysteresis measurements were done at room temperature using an automatic P –E loop tracer based on Sawyer–Tower circuit.Piezoelectric charge co-efficient d 33was measured using a Berlincourt d 33meter after poling the samples in silicone–oil bath at 2008C for half an hour under a dc electric field of 60–70kV/cm.3.Results and discussion3.1.Structural and micro-structural studiesThe phase formation and crystal structure of the ceramics were examined by X-ray diffraction (XRD),which is shown in Fig.1.The XRD patterns of the samples show the characteristic peaks of SBT.The peaks have been indexed with the help of a computer program–POWDIN [21]and the refined lattice parameters are given in Table 1.It is observed that a single phase layered perovskite structure is maintained in the range 0.0 x 0.05.Owing to the same co-ordination number i.e.6and the smallerionic radius of W (0.60A˚)in comparison to Ta (0.64A ˚),there is a high possibility of tungsten occupying the tantalum site.The observance of unidentified peak of very low intensity in the compositions with x >0.05indicates the solubility limit of W concentration in SBT.The unidentified peak is possibly due to tungsten not occupying the Ta sites in the structure as the intensity of this peak is observed to increase with tungsten content.Composition and sintering temperature influences the micro-structure such as grain growth and densification of the specimen,which in turn control other properties of the material [11,13].The effects of W substitution on the microstructure have been examined by SEM and the obtained micrographs are shown in Fig.2.It shows the microstructure of the fractured surface of the studied samples.It is clearly observed that W substitution has pronounced effect on the average grain size and homogeneity of the grains.Randomly oriented and anisotropic plate-like grains are observed in all the samples.It is also observed that the average grain size increases gradually with increasing W content.The average grain size in the sample with x =0.0is $2–3m m while that in the sample with x =0.20the size increases to $5–7m m.3.2.Electrical studiesThe electrical conductivity of ceramic materials encompasses a wide range of values.In insulators,the defects w.r.t.the perfect crystalline structure act as charge carriers and the consideration of charge transport leads necessarily to the consideration of point defects and their migration [22].Many mechanisms were put forward to explain the conductivity mechanism in ceramics.Most of them are approximately divided into three groups:electronic conduction,oxygen vacancies ionic conduction,and ionic and p-type mixed conduction [22].Intrinsic conductivity results from the movement of the component ions,whereas conduction resulting from the impurity ions present in the lattice is known as extrinsic conductivity.At low temperature region (ferroelectric phase),the conduction is dominated by the extrinsic conduction,whereas the conduction at the high-temperature paraelectric phase ($300–7008C)is dominated by the intrinsic ionic conduction [23,25].Fig.3shows the temperature dependence of dc conductivity (s dc )for the undoped and doped SBT samples.The curves show that the conductivity increases with temperature.This is indicative of negative temperature coefficient of resistance (NTCR)behavior,a characteristic of dielectrics [22].It is observed in Fig.3that throughout the temperature range,the dc conductivity of the doped samples are nearly two to three orders lower than that of the undoped sample.Two predominant conduction mechanisms indicated by slope changes in the two different temperature regions are observed in Fig.3.Such changes in the slope in the vicinity of the ferro-paraelectric transition region have been observed in other ferroelectric materials as well [23,24].In addition,it is also observed (Table 2)that the activation energy calculated using the Arrhenius equation [22]in the paraelectric phase increase from $0.80eV for the undoped sample to $2eV for the doped samples.The X-ray photoemission spectroscopic study has confirmed that when Bi 2O 3evaporates during high-temperature processing,vacancy complexes are formed in the (Bi 2O 2)2+layers [26].As a result,defective (Bi 2O 2)2+layers are inherently present in SBT.The undoped SBT shows n-type conductivity,since when oxygen vacancies are created,it leaves behind two trapped electrons [27]:O o !12O 2"þV o þ2e 0(1)where O o is an oxygen ion on an oxygen site,V o is a oxygen vacant site and e 0represents electron.The conductivity in the perovskites can be described as an ordered diffusion of oxygen vacancies [28].Their motion is manifested by enhanced ionic conductivity associated with an activation energy value of $1eV [26].These oxygen vacancies can be suppressed by addition of donors,since the donor oxide contains more oxygen per cation than the host oxide it replaces [29].It has been reported that conductivity in Bi 4Ti 3O 12(BIT)can be significantly decreased,up to three orders of magnitude with the addition of donors,such as Nb 5+and Ta 5+at the Ti 4+sites [23,30].A few other studies on layered perovskites have also reported a decrease inconductivityFig.1.XRD patterns of SrBi 2(W x Ta 1Àx )2O 9samples sintered at 12008C.Table 1Lattice parameters of SrBi 2(W x Ta 1Àx )2O 9samples.Concentration of W a (A ˚)b (A ˚)c (A ˚)0.0 5.5212 5.513924.92230.025 5.5214 5.520225.10790.05 5.5217 5.519925.05850.075 5.5191 5.504525.05670.10 5.5142 5.506125.0850.205.51335.493925.0861I.Coondoo et al./Materials Research Bulletin 44(2009)1288–12921289with addition of donors [23,24,31].In the present study,the Ta 5+-site substitution by W 6+in SBT can be formulated using a defect chemistry expression as WO 3þV o!Ta 2O 512W Ta þ3O o (2)It shows that the oxygen vacancies are reduced upon the substitution of donor W 6+ions for Ta 5+ions.Hence,it is reasonable to believe that the conductivity in SBT is suppressed by donor addition.As per the above discussion,the high s dc observed in the undoped SBT (Fig.3)can be attributed to the motion of oxygen vacancies.As already discussed,the doped samples show reduced conductivity because the transport phenomena involving oxygen vacancies are greatly reduced.The high E a value of $1.75–2eVcorresponding to the high-temperature region in the doped ceramics is consistent with the fact that in the donor-doped materials,the ionic conduction reduces [32].The activation energy E a in the low temperature ferroelectric region (Table 2)corre-sponds to extrinsic conduction.At lower temperatures the extrinsic conductivity results from the migration of impurity ions in the lattice.Some of these impurities may also be associated with lattice defects.Pure SBT has large number of Schottky defects (oxygen vacancies)in addition to impurity ions whereas in the doped samples,due to charge neutrality,there is relatively less content of oxygen vacancies.Thus,in the doped samples the conductivity in the low temperature region is largely due to the impurity ions only.This explains the high activation energy in pure SBT in the low temperature region compared to doped samples (Table 2).In the high-temperature region,the value of E a in the doped samples is observed to increase with W concentration up to x =0.05but beyond that,it decreases (Table 2).The decrease in the activation energy for samples with x >0.05suggests an increase in the concentration of mobile charge carriers [33].This observation can be ascribed to the existence of multiple valence states of tungsten.Since tungsten is a transitional metal element,the valence state of W ions in a solid solution most likely varies from W 6+to W 4+depending on the surrounding chemical environment [34].When W 4+are substituted for the Ta 5+sites,oxygen vacancies would be created,i.e.one oxygen vacancy would be created for every two tetravalent W ions entering the crystal structure,whichFig.3.Variation of dc conductivity with temperature in SrBi 2(W x Ta 1Àx )2O 9samples.Fig.2.SEM micrographs of fractured surfaces of SrBi 2(W x Ta 1Àx )2O 9samples with (a)x =0.0,(b)x =0.025,(c)x =0.050,(d)x =0.075,(e)x =0.10and (f)x =0.20Table 2Activation energy (E a )in the high-temperature paraelectric region and low temperature ferroelectric region;Curie temperature (T c )in SrBi 2(W x Ta 1Àx )2O 9samples.Concentration of W E a (high temp.)(eV)E a (low temp.)(eV)T c (8C)0.00.790.893110.025 1.920.593080.05 1.960.543250.075 1.940.543380.10 1.860.573680.201.740.54390I.Coondoo et al./Materials Research Bulletin 44(2009)1288–12921290explains the increase in the concentration of mobile charge carriers which ultimately results in an decrease in the E a beyond x>0.05. Hence it is reasonable to conclude that W ions in the SBWT exists as a varying valency state,i.e.at lower doping concentration they exist in hexavalent state(W6+)and at a higher doping concentra-tion,they tend to exist in lower valency states[8].The P–E loops of SrBi2(Ta1Àx W x)2O9are shown in Fig.4.It is observed that W-doping results in formation of well-defined hysteresis loops.Fig.5shows the compositional dependence of remanent polarization(2P r)and the coercivefield(2E c)of SrBi2(Ta1Àx W x)2O9samples.Both the parameters depend on W content of the samples.It is observed that2P rfirst increases with x and then decreases while2E cfirst decreases with x and then increases(Fig.5).The optimum tungsten content for maximum2P r ($25m C/cm2)is observed to be x=0.075.It is known that ferroelectric properties are affected by compositional modification,microstructural variation and lattice defects like oxygen vacancies[10,35,36].In hard ferroelectrics, with lower valent substituents,the associated oxide vacancies are likely to assemble in the vicinity of domain walls[37,38].These domains are locked by the defects and their polarization switching is difficult,leading to an increase in E c and decrease in P r[38]. On the other hand,in soft ferroelectrics,with higher valent substituents,the defects are cation vacancies whose generation in the structure generally increases P r.Similar observations have been made in many reports[38–41].Watanabe et al.[42]reported a remarkable improvement in ferroelectric properties in the Bi4Ti3O12ceramic by adding higher valent cation,V5+at the Ti4+ site.It has also been reported that cation vacancies generated by donor doping make domain motion easier and enhance the ferroelectric properties[43].Further,it is known that domain walls are relatively free in large grains and are inhibited in their movement as the grain size decreases[44].In the larger grains, domain motion is easier which results in larger P r.Also for the SBT-based system,it is known that with increase in the grain size the remanent polarization also increases[45,46].Based on the obtained results and above discussion,it can be understood that in the undoped SBT,the oxygen vacancies assemble at sites near domain boundaries leading to a strong domain pinning.Hence,as observed,well-saturated P–E loop for pure SBT is not obtained.But in the doped samples,the suppression of the oxygen vacancies reduces the pinning effect on the domain walls,leading to enhanced remanent polarization and lower coercivefield.Also,the increase in grain size in tungsten added SBT,as observed in SEM micrographs(Fig.2)contribute to the increase in polarization values.In the present study,the grain size is observed to increase with increasing W concentration.However, the2P r values do not monotonously increase and neither the E c decreases continuously with increasing W concentration(Fig.5). The variation of P r and E c beyond x>0.05,seems possibly affected by the presence of secondary phases(observed in XRD diffracto-grams),which hampers the switching process of polarization [47–50].Also,beyond x>0.05the increase in the number of charge carriers in the form of oxygen vacancies leads to pinning of domain walls and thus a reduction in the values of P r and increase in E c is observed.Fig.6shows the variation of piezoelectric charge coefficient d33 with x in the SrBi2(Ta1Àx W x)2O9.The d33values increases with increase in W content up to x=0.05.A decrease in d33values is observed in the samples with x!0.075.The piezoelectric coefficient,d33,increases from13pC/N in the sample with x=0.0to23pC/N in the sample with x=0.05.It is known that the major drawback of SBT is its relatively higher conductivity,which hinders proper poling[51].High resistivity is therefore important for maintenance of poling efficiency at high-temperature[52,53].The W-doped SBT samples show an electrical conductivity value up to three orders of magnitude lower than that of undoped sample(Fig.3).The positional variation of2P r and2E c in SrBi2(W x Ta1Àx)2O9samples.Fig.6.Variation of d33in SrBi2(W x Ta1Àx)2O9samples.Fig. 4.P–E hysteresis loops in SrBi2(W x Ta1Àx)2O9samples recorded at roomtemperature.I.Coondoo et al./Materials Research Bulletin44(2009)1288–12921291decrease in conductivity upon donor doping improve the poling efficiency resulting in the observed higher d33values.Moreover, since the grain size increases with W content in SBT,it is reasonable to believe that the increase in grain size will also contribute to the increase in d33values[54].The decrease in the value of d33for samples with x!0.075is possibly due to the presence of secondary phases as observed in diffractograms[1,51,55]and the increase in oxygen vacancies for samples with x>0.05.4.ConclusionsX-ray diffractograms of the samples reveal that the single phase layered perovskite structure is maintained in the samples with tungsten content x0.05.SEM micrographs reveal that the average grain size increases with increase in W concentration. The temperature dependence of the electrical conductivity shows that tungsten doping results in the decrease of conductivity by up to three order of magnitude compared to W free SBT.All the tungsten-doped ceramics have higher2P r than that of the undoped sample.The maximum2P r($25m C/cm2)is obtained in the composition with x=0.075.The reduced conductivity allows high-temperature poling of the doped samples.Such compositions with low loss and high P r values should be excellent materials for highly stable ferroelectric memory devices.The d33value is observed to increase with increasing W content up to x0.05.The value of d33 in the composition with x=0.05is$23pC/N as compared to$13 pC/N in the undoped sample.AcknowledgmentsThe authors sincerely thank Prof.P.B.Sharma,Dean,Delhi College of Engineering,India for his generous support and providing ample research infrastructure to carry out the research work.The authors are thankful to Dr.S.K.Singhal,Scientist, National Physical 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包装工程第44卷第19期·104·PACKAGING ENGINEERING2023年10月层状双金属氢氧化物/聚乙烯醇气体阻隔薄膜材料制备及性能研究张子怡，李梦冉，薛程，范婷婷，李欢欢，李中波*（安徽农业大学轻纺工程与艺术学院，安徽合肥230036）摘要：目的研发出一种具有优异氧气阻隔性能的柔性薄膜，其在食品包装领域具有良好的应用前景。

方法以具有生物降解性能的聚乙烯醇（PVA）为成膜基材，镁铝层状双金属氢氧化物（MgAl-LDH）为改性剂，柠檬酸为交联剂，采用流延法制备出具有优异气体阻隔性能的PVA/MgAl-LDH复合薄膜。

结果随着柠檬酸的含量的增加，复合薄膜的亲水性能逐渐增加，阻隔性能逐渐下降；随着复合薄膜中MgAl-LDH的含量的增加，复合薄膜的疏水性能和阻隔性能逐渐提高。

当复合薄膜中MgAl-LDH的质量分数为1.5%时，薄膜的力学性能最好，抗拉强度为42 MPa，断裂伸长率为16.7%，此MgAl-LDH质量分数下薄膜的气体阻隔性能也最优异，气体透过量为16 mL/(m2·24 h·0.1 MPa)。

结论柠檬酸的引入增加了薄膜内部亲水基团的数量，提升了复合薄膜的亲水性能。

MgAl-LDH可以减少PVA薄膜内部自由体积，提升PVA薄膜的力学性能和阻隔性能。

关键词：聚乙烯醇；镁铝层状双金属氢氧化物；柠檬酸；复合薄膜；阻隔性能中图分类号：TS206.4 文献标识码：A 文章编号：1001-3563(2023)19-0104-08DOI：10.19554/ki.1001-3563.2023.19.014Preparation and Properties of PVA/MgAl-LDH Gas Barrier FilmsZHANG Zi-yi, LI Meng-ran, XUE Cheng, FAN Ting-ting, LI Huan-huan, LI Zhong-bo*(College of Light Textile Engineering and Art, Anhui Agricultural University, Hefei 230036, China)ABSTRACT: The work aims to develop a flexible film with excellent oxygen barrier performance and good application prospects in the field of food packaging. The PVA/MgAl-LDH composite film with excellent gas barrier performance was prepared by the casting method with biodegradable polyvinyl alcohol (PVA) as the film-forming substrate, mag-nesium-aluminum layered bimetallic hydroxide (MgAl-LDH) as the modifier, and citric acid as the cross-linking agent.The experimental results showed that with the increase of citric acid content, the hydrophilic property of the composite film gradually increased and the barrier performance decreased gradually. With the increase of MgAl-LDH content in the composite film, the hydrophobic property and barrier property of the composite film gradually increased. When the content of MgAl-LDH in the composite film was 1.5%, the mechanical properties of the film were the best, with a ten-sile strength of 42 MPa and an elongation at break of 16.7%. The gas barrier performance of the film with this MgAl-LDH content was also the best, with a gas permeability of 16 mL/(m2·24 h·0.1 MPa). In addition, the introduc-tion of citric acid increases the number of hydrophilic groups inside the film, and the hydrophilic properties of the composite film are enhanced. MgAl-LDH can reduce the free volume inside the PVA film and enhance the mechanical收稿日期：2023-04-27基金项目：安徽省教育厅自然科学重点项目（2022AH050875）；安徽省科技重大专项（202103a06020005）；安徽省大学生创新创业项目（S202120364214）第44卷第19期张子怡，等：层状双金属氢氧化物/聚乙烯醇气体阻隔薄膜材料制备及性能研究·105·and barrier properties of the PVA film.KEY WORDS: polyvinyl alcohol; magnesium-aluminum layered bimetallic hydroxide; citric acid; composite film; bar-rier performance阻隔性薄膜指对气体、有机化合物等低分子量的化学物质具有非常低的透过性的薄膜。

太原理工大学硕士研究生学位论文钠离子电池正极材料P2型Na x MnO2的制备和电化学性能研究摘要锂离子电池在便携电子设备、电动汽车等领域已经得到了广泛的应用，并且取得了巨大的成功且增长势头十分迅猛。

然而，锂资源储量较低导致锂离子电池成本不断升高，钠离子电池有望在大规模储能设备方面取代锂离子电池。

在众多钠离子电池正极材料中，层状过渡金属氧化物特别是钠锰氧化物具有高比容量和工作电压、易于制备、环境友好无毒性、成本低等优点得到了研究者广泛的关注，此外，与O3相结构相比，P2相结构具有较高的离子导电性和较低的扩散势垒。

因此，P2型锰基层状氧化物是一种极具潜力的钠离子电池正极材料。

本文探究了不同高温反应温度和不同高温反应时间及Cu2+掺杂对P2-Na0.67MnO2材料的影响；制备具有双极性特性的P2-Na0.5Ni0.25Mn0.75O2材料，对其进行Ti4+掺杂改性，并进一步研究Ti4+掺杂对Na0.5Ni0.25Mn0.75O2结构、形貌、电化学性能以及离子扩散速率的影响。

本论文主要研究结果如下：(1) 在采用高温固相法制备P2-Na0.67MnO2的过程中，不同的高温反应温度制备的材料晶格结构没有明显改变，其中温度在900℃时合成材料的结晶度最好，不同温度下合成材料的形貌均为微米级块状并存在一定程度的团聚现象。

900℃和1000℃合成的材料具有相似的高于150 mAh g-1的可逆容量，但是900℃制备的材料循环性能更好，100周容量保持率为78.1%，并且倍率性能明显优于1000℃合成的材料。

(2) 在900℃不同高温反应时间内，随着反应时间的延长，材料放电容量逐渐增大，当高温反应时间为15h时电化学性能最佳，首周放电容量可达164.8 mAh g-1，循环100周容量保持率为84.7%。

当反应时间过长达到I太原理工大学硕士研究生学位论文20h时，材料中会产生MnO2杂质并且放电容量会降低。

(3) Cu2+掺杂明显改变了材料的晶格结构，材料由正交晶系转变为六方晶系，掺杂量过高时会产生CuO杂质，但是掺杂之后材料形貌并没有明显的改变，仍然是微米级块状形貌。

第42卷㊀第5期2021年5月发㊀光㊀学㊀报CHINESE JOURNAL OF LUMINESCENCEVol.42No.5May,2021㊀㊀收稿日期:2020-12-15;修订日期:2021-02-02㊀㊀基金项目:国家自然科学基金(51672167);西安市科技计划(201805027YD5CG11);陕西师范大学创新创业训练计划项目(S202010718057)资助Supported by National Natural Science Foundation of China(51672167);Science and Technology Project of Xi a n(201805027YD5CG11);Innovation and Entrepreneurship Training Program of Shaanxi Normal University(S202010718057)†共同贡献作者文章编号:1000-7032(2021)05-0642-08Ba 2+调制SrGe 4-x O 9ʒx Mn 4+晶体结构及其发光性质魏恒伟1,2†,李雅婷1†,凌钰婷1,林继周1,刘天用3,何地平2,焦㊀桓1∗(1.陕西师范大学,化学化工学院,陕西西安㊀710062;2.陕西师范大学,基础实验教学中心,陕西西安㊀710062;㊀3.烟台希尔德新材料有限公司,山东烟台㊀264006)摘要:采用传统固相法在1100ħ合成了SrGe 4-x O 9ʒx Mn 4+(SGOM)系列荧光粉,通过Ba 2+取代Sr 2+调制了荧光粉基质的局部结构,对样品的晶体结构㊁发光性质和热稳定性进行了探讨㊂XRD 测试结果表明,Mn 4+和Ba 2+均成功地掺杂进入基质SrGe 4O 9晶格,没有其他物相产生㊂在275nm 紫外光激发下,SGOM 荧光粉的发射光谱是位于600~750nm 的深红色谱带,峰值波长位于660nm,主要源于Mn 4+离子2E g ң4A 2g 能级跃迁的窄带发射,优化的Mn 4+浓度为0.015㊂利用Ba 2+离子对SrGe 3.985O 9ʒ0.015Mn 4+荧光粉的发光性质进行调控,发现随着Ba 2+浓度增大,发射光谱的强度先上升后下降,最佳Ba 2+浓度为0.4㊂Ba 2+离子的引入造成基质结构中Sr1O10多面体产生局部扩张,导致样品的发射光谱展宽㊂为了解决封装白光LED 中有机材料存在的难以承受发热的问题,制备出了基于SrGe 3.985O 9ʒ0.015Mn 4+荧光粉的荧光玻璃㊂优良的发光性质和热稳定性使SGOM 荧光粉具备了应用于白光LED 器件的前景㊂关㊀键㊀词:晶体结构;SGOM 荧光粉;Ba 2+调制;荧光玻璃中图分类号:O482.31㊀㊀㊀文献标识码:A㊀㊀㊀DOI :10.37188/CJL.20200386Crystal Structure and Luminescent Properties of Ba 2+Modulated SrGe 4-x O 9ʒx Mn 4+PhosphorsWEI Heng-wei 1,2†,LI Ya-ting 1†,LING Yu-ting 1,LIN Ji-zhou 1,LIU Tian-yong 3,HE Di-ping 2,JIAO Huan 1∗(1.School of Chemistry &Chemical Engineering ,Shaanxi Normal University ,Xi an 710062,China ;2.Basic Experiment Center ,Shaanxi Normal University ,Xi an 710062,China ;3.Shield Advanced Material Technology Company ,Yantai 264006,China.)∗Corresponding Author ,E-mail :jiaohuan @Abstract :A series of SrGe 4-x O 9ʒx Mn 4+(SGOM)phosphors were prepared at 1100ħby traditionalsolid-state method.The crystal structure,luminescent properties and temperature-dependent of SGOM were investigated.Local structure of SrGe 4O 9(SGO)was modulated by the introducing of Ba 2+ions.The results of XRD showed that both Mn 4+and Ba 2+ions were successfully doped into the SGO,and no otherimpurity phase was detected.Fluorescent measurement indicates that SGOM phosphors produce red emis-sion(600~750nm)upon UV(275nm)light excitation,which can be attributed to 2E g ң4A 2g of Mn 4+.The optimal Mn 4+concentration in these phosphors equals 0.015.The emission spectra of SrGe 3.985O 9ʒ0.015Mn 4+was tuned by the introducing of Ba 2+ions.The luminescent intensity of SGOM was improved㊀第5期魏恒伟,等:Ba2+调制SrGe4-x O9ʒx Mn4+晶体结构及其发光性质643㊀up to50%when the Ba2+doping concentration is0.4,and an emission spectra broadening was also ob-served.This phenomenon is thought to be originated from the expanding of the local structure of Sr1O10 polyhedron caused by the Ba2+doping.The phosphor-in-glass(PiG)technique was used to explore the properties of SGOM phosphor to overcome the decomposing issue of the organic materials.These phos-phors exhibit potential application in WLED.Key words:crystal structure;SGOM phosphors;Ba2+modulated;phosphor in glass1㊀引㊀㊀言白光LED作为固态照明光源具有高流明效率㊁低能耗㊁长使用寿命以及环境友好等优点,被广泛应用于显示与照明领域[1-3]㊂但由于目前普遍采取的方案中缺少红光成分[4-6],导致封装的灯具存在显色指数低㊁色温高等问题㊂寻找合适的红色荧光粉是解决这一问题的关键所在㊂荧光材料通常以氧化物㊁硫化物㊁氟化物以及氮化物作为基质材料,将稀土离子(Eu2+㊁Ce3+)或过渡区金属离子(Mn4+㊁Bi3+㊁Cr3+)引入基质产生不同波长的发光[7-12]㊂以Eu2+为激活剂获得红色荧光粉的发射光谱半峰宽大,合成条件(还原性气氛)苛刻㊂例如,Schnick等[13]合成的Sr2[BeAl3N4]ʒEu2+红色荧光粉,Sohn等[9]发现的新型Ba2-x-LiAlS4ʒEu2+荧光粉,在应用过程中没有明显优势㊂由于Mn4+离子的2E gң4A2g能级跃迁可产生窄带的红光发射,掺杂到氧化物(铝酸盐和锗酸盐)㊁氟(氧)化物等基质中,可得到发射光谱范围为600~ 750nm的红色光发射的荧光粉,而以Mn4+为激活剂的窄带红粉在发光特性上可以满足LED照明器件的要求㊂但制备过程中大多使用氢氟酸,对环境造成了污染㊂例如,陈学元等[14]报道了非稀土掺杂的红色发光的K2SiF6ʒMn4+荧光粉,焦桓等[15]报道了发射红光的K3TaO2F4ʒMn4+荧光粉㊂因而研究人员对于氧化物基质的窄带红粉寄予了希望㊂彭明营等[16]发现了具有红光发射的Sr4Al12O25ʒMn4+荧光粉,尤洪鹏等[17]介绍了CaAl12O19ʒMn4+红色荧光粉,这些荧光粉性能优良,但是存在合成条件苛刻㊁热稳定性有待改进等问题㊂与铝酸盐相比,锗酸盐的合成条件比较温和,有可能获得具有红色光的发光材料㊂胡义华等[7-8]报道了SrGe4O9ʒMn4+和BaGe4O9ʒMn4+红色荧光粉㊂Park等[18]初步研究了Sr1-x Ba x-Ge4O9ʒ0.005Mn4+(0.00ɤxɤ1.00)荧光粉的发光,但未对基质局部结构与发光性能间的关系进行细致的分析,调控不系统㊂结构调控是发光性质调整的重要途径,因而本文选取SrGe4O9为基质材料,详细研究了Mn4+掺杂SrGe4O9和Ba2+调制SrGe4-x O9ʒx Mn4+荧光粉的晶体结构与发光性质之间的关系㊂通过Rietveld方法对基质的X射线衍射数据进行精修,分析晶体结构的局部变化对发光性质的影响,进一步讨论发射光谱展宽的原因㊂为了克服传统封装白光LED过程中有机材料存在的问题,将所合成发光强度最高的样品与二氧化硅玻璃粉相结合,制备出了荧光玻璃,并测试其基本性能㊂该荧光粉具有紫外激发㊁红色发射的性能,具备了应用于白光LED器件的基本条件㊂2㊀实㊀㊀验2.1㊀样品合成采用传统固相法制备了Sr1-y Ge4-x O9ʒx Mn4+, y Ba2+(x=0.0~0.03;y=0.0~0.6)系列荧光粉㊂按化学计量比称取如下实验原料:BaCO3(AR)㊁SrCO3(AR)㊁GeO2(AR)和MnCO3(AR)㊂将称取的原料置于玛瑙研钵中,加入少量无水乙醇研磨30min,混和均匀后装入Al2O3坩埚㊂将装有样品的坩埚在箱式烧结炉中于1100ħ烧结6h,而后随炉冷却至室温,研磨得粉末状样品㊂荧光玻璃的制备:将选取的荧光粉与二氧化硅玻璃粉(24.58SiO2-1.25Al2O3-1.48NaCO3-0.25BaCO3-0.60KCO3-11.33H3BO3)按一定比例放入粉体混合机(GH-5,上海振春粉体设备有限公司)中进行研磨,利用冷等静压机(LDJ630/3000-300S)将混匀的原料压制成型后,装入Al2O3坩埚,置于箱式电阻炉(SX-4-10,北京科伟永兴仪器有限公司)中进行烧结㊂程序结束后,自然降温至室温取样并进行表征㊂2.2㊀样品测试表征利用MiNiFlex600型X射线衍射仪(XRD)对合成的样品进行物相表征,辐射源为Cu Kα靶(λ= 0.15406nm),工作条件为40kV和15mA,步长644㊀发㊀㊀光㊀㊀学㊀㊀报第42卷0.02ʎ,扫速分别为2(ʎ)/min 和10(ʎ)/min,数据收集范围2θ=10ʎ~80ʎ㊂采用日本HITACHI F-4600荧光光谱仪结合热猝灭分析仪(TAP-02)对样品的光谱和热稳定性进行测试和记录,光源为450W Xe 灯,光电倍增管电压400V,入射和出射狭缝为5nm,扫描速率240nm/min㊂使用FLS-980稳态瞬态光谱仪(英国爱丁堡公司)测试样品的荧光寿命,激发波长为275nm,发射波长为660nm,光源为微秒灯㊂利用紫外-可见近红外光谱仪(Lambd 1050,美国Perkin-Elmer 公司)测试荧光玻璃片的透射光谱㊂3㊀结果与讨论3.1㊀SrGe 4O 9物相和结构图1为SrGe 4O 9粉末X 射线衍射图和晶体结构示意图,通过对基质的XRD 进行Rietveld 精修拟合(如图1),本文所合成SrGe 4O 9的晶胞参数为a =b =1.13580nm,c =0.47607nm,V cell =0.5318753nm 3,Z =3,该数据与Fumito Nishi 报道基本一致[19]㊂详细的晶体学参数见表1,结构中原子的位置㊁占有率以及温度因子见表2㊂图1内插图为沿[001]方向SrGe 4O 9的晶体结构示意图㊂红色圆球为Sr 2+离子,蓝色圆球为Ge 4+离子,青蓝色圆球为O 2-离子㊂SrGe 4O 9晶体结构的空间群为P 321(No.150)㊂该结构具有特征的三次轴,Ge1O6和Ge2O6八面体分别与Ge3O4和Ge4O4四面体共顶点连接,形成基质的骨架结构㊂Sr 2+离子填充于孔道之间,形成Sr1O10多面体,平衡结构中的电荷,维持结构稳定㊂202兹/（°）I n t e n s i t y /c o u n t s100000800006000040000200000-1000010304050607080Sr1Sr1Sr1Sr1Sr1Sr1Ge3Ge1Ge3Ge3Ge4Ge2Ge2Ge4Ge4Ge4Ge4Ge4acb 图1㊀Rietveld 精修拟合SrGe 4O 9的X 射线衍射图谱(蓝圈:观察点;红线:计算点;黑线:误差),内插图:沿[001]方向SrGe 4O 9的晶体结构示意图㊂Fig.1㊀Observed(blue dots)and calculated(red line)powder XRD patterns as well as difference profile(black line)for the Ri-etveld structure analysis of SrGe 4O 9.Inset:crystal structure of SrGe 4O 9along [001].表1㊀SrGe 4O 9Rietveld 精修XRD 的晶体学参数Tab.1㊀Crystallographic data of SrGe 4O 9derived from Rietveld refinement of powder XRD dataFormulaCrystal system Space groupRadiationLatticeparameters a /nmc /nmV cell /nm 3Formula unit per cell,ZSrGe 4O 9TrigonalP 321(No.150)Cu Kα11.135800.476070.53187533FormulaStructurerefinementT /KProfile rangeNumber ofdata ProfilefuncationR exp /%R wp /%R p /%GOFSrGe 4O 9Topas 29310ʎ~80ʎ7002PV_MOD2.327.855.653.38表2㊀结构精修获得的SrGe 4O 9原子位置、占有率和温度因子Tab.2㊀Atomic coordinates,site occupancies and temperature factors for SrGe 4O 9determined by Rietveld refinement on powderXRD dataSiteNp.xyz Atom.Occ.B eq .Sr13e 0.328000.000000.00000Sr 2+11Ge11a 0.00000.00000.0000Ge 4+11Ge22d0.333330.666670.10760Ge 4+11Ge33f0.820900.00000.50000Ge 4+11㊀第5期魏恒伟,等:Ba 2+调制SrGe 4-x O 9ʒx Mn 4+晶体结构及其发光性质645㊀表2(续)SiteNp.xyz Atom.Occ.B eq .Ge46g 0.490800.341000.39900Ge 4+11O13f0.511200.000000.50000O 2-11O26g 0.602200.422200.12450O 2-11O36g 0.154600.061600.76360O 2-11O46g 0.325500.214500.29490O 2-11O56g 0.510200.249600.67220O 2-113.2㊀SrGe 4-x O 9ʒx Mn 4+荧光粉的物相分析图2为SrGe 4-x O 9ʒx Mn 4+(x =0.002~0.030)系列荧光粉的X 射线衍射图谱㊂所合成样品的XRD 谱线均与PDF No.14-0029标准卡片一致,无杂峰出现,即所得样品均为纯相SrGe 4O 9㊂在六配位的环境中,Ge 4+(r Ge =0.053nm)与Mn 4+离子半径(r Mn =0.053nm )相等㊂当向基质SrGe 4O 9中引入Mn 4+离子时,Mn 4+取代Ge 4+进入晶格,不会对基质结构产生影响㊂20602θ/（°）I n t e n s i t y /a .u .SrGe 4-x O 9∶x Mn 4-10304050PDF No.14鄄0029x =0.002x =0.005x =0.010x =0.015x =0.020x =0.025x =0.030图2㊀SrGe 4-x O 9ʒx Mn 4+荧光粉的X 射线衍射图谱Fig.2㊀XRD pattern of SrGe 4-x O 9ʒx Mn 4+phosphor3.3㊀SrGe 4-x O 9ʒx Mn 4+荧光粉的发光性质对SrGe 4-x O 9ʒx Mn 4+(x =0.002~0.030)系列荧光粉的发光性能进行了测试,结果如图3所示㊂图3(a)为选取样品(x =0.015)的激发和发射光谱㊂由图可知,检测波长为660nm 时,样品的激发光谱为位于200~520nm 的宽带,包含两个明显的激发峰,分别位于275nm 和430nm㊂前者源于4A 2ң4T 1跃迁,后者为4A 2ң4T 2跃迁㊂采用275nm 紫外和430nm 蓝光分别对样品进行激发,发射光谱均位于660nm,光谱范围为600~750nm,可归属为Mn 4+3d 3电子层间2E 2g ң4A 2g 之间的跃迁,这与胡义华等[8]报道的结果基本一致,表明该类荧光粉与紫外芯片和蓝光芯片可以很好地匹配㊂图3(b)为275nm 和430nm 激发系列样品的发光强度随x 的变化趋势图㊂其中以275nm 紫外光激发时,样品的发射强度较高,是以430nm 蓝光激发发射强度的6倍㊂随着x 值增加,样品的发光强度上升,当x =0.015时达到最大,而后由于浓度猝灭现象的产生导致发光强度下降㊂0.8300700姿/nmN o r m a l i z e d i n t e n s i t y姿ex =430nm姿ex =275nm EM200400500600650750EX1.00.60.40.20（a ）姿em =660nmSrGe 3.985O 9∶0.015Mn 4+0.300Mn 4+content xI n t e n s i t y /a .u .姿ex =430nm0.02030000800060000（b ）400005000040002000姿ex =275nm 0.0250.0150.0100.0050图3㊀(a)选取样品SrGe 3.985O 9ʒ0.015Mn 4+的归一化激发㊁发射光谱;(b)SrGe 4-x O 9ʒx Mn 4+(x =0.002~0.030)发射光谱强度变化㊂Fig.3㊀(a)Normalized excitation (EX)and emission (EM)spectra of the selected SrGe 3.985O 9ʒ0.015Mn 4+.(b)Dependence of the PL intensity on the Mn 4+content xin the SrGe 4-x O 9ʒx Mn 4+(x =0.002-0.030)system.3.4㊀Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+荧光粉的物相及发光性质阴阳离子取代是对荧光粉的发光性能进行改进和调控的常用手段[20]㊂基于SrGe 3.985O 9ʒ0.015Mn 4+荧光粉,本文以Ba 2+取代基质中的Sr 2+㊂当一部分Ba 2+进入Sr 2+格位后,Sr1O10多面体转变为(Sr1/646㊀发㊀㊀光㊀㊀学㊀㊀报第42卷Ba)O10多面体,Ba 2+离子半径(r Ba =0.0135nm)大于Sr 2+离子半径(r Sr =0.0118nm),致使GeO6和GeO4局部环境产生变化㊂由于Mn 4+对配位环境的变化非常敏感[14],故可实现对其发光性能的调控㊂图4(a)是Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+系列荧光粉的XRD㊂观察可知随着Ba 2+含量y 值的增加,样品的所有衍射峰与标准卡片相吻合,表明Ba 2+成功地取代了部分Sr 2+,基质结构并未发生改变㊂通过对系列样品的仔细分析,发现衍射峰(111)随y 值增大逐渐宽化,说明Ba 2+浓度升高会导致样品的结晶性降低㊂对所得样品的XRD 进行Rietveld 精修拟合,其晶胞参数的变化如图4(b)所示㊂a 随着y 值上升从1.1358nm 增大到1.1524nm;c 为0.4753nm,基本不受y 值影响;晶胞体积V cell 呈上升趋势,由0.531875nm 3增大到0.546618nm 3,进一步证明Ba 2+进入了基质结构㊂10502兹/（°）I n t e n s i t y /a .u .60403020PDF No.14鄄0029x =0x =0.10x =0.20x =0.30x =0.40x =0.50x =0.60(111)24252兹/（°）（a ）Sr 1-y Ge 3.985O 9∶0.015Mn 4+,y Ba 2+0.4Ba2+content ya a n d c /n m0.30.20（b ）Sr 1-y Ge 3.985O 9∶0.015Mn 4+,y Ba 2+c0.51.161.171.151.141.131.120.4950.4800.4650.10.6V cell 0.5320.53６0.5４０0.5４４0.5４８Ｖc e l l /n m 3a 图4㊀(a)Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0.0~0.6)荧光粉的XRD 谱图;(b)晶胞参数a ㊁c 和V cell随Ba 2+浓度的变化㊂Fig.4㊀(a)XRD patterns of Sr 1-y Ge 3.985O 9ʒ0.015Mn4+,y Ba 2+(y =0.0~0.6)phosphor.(b)Cell parametera ,c and V cell varied with Ba 2+concentration.图5(a)是Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+系列荧光粉的发光强度变化㊂随Ba 2+含量y 值增大,样品的发光强度不断上升;当y =0.4时,发光强度达到最大,较未掺杂样品的发光强度提升约50%;当y >0.4时,发光强度开始下降㊂结合衍射数据(图4(b)),可以发现随Ba 2+浓度增大,尽管样品的衍射峰位和数量没有变化,但衍射峰出现宽化,表明样品的结晶性降低,导致荧光粉发光强度降低㊂为了体现Ba 2+离子对荧光粉发射光谱的调制作用,给出了样品归一化的发射光谱,如图5(b)所示㊂样品在275nm 紫外光激发下产生红光发射,P1(642nm)㊁P2(655nm)㊁P3(665nm)和P4(670nm)主要源于Mn 4+进入GeO6八面体形成MnO6,导致2E g 和2T 2g ң4A 2g 跃迁发射自旋和宇称双重禁阻[7,21]㊂随着Ba 2+的引入,主峰位(660nm)基本上没有移动,样品发射光谱的峰形展宽,这是由于Ba 2+含量增加,基质晶格扩张,使P1㊁P2㊁P3和P4峰位处的相对强度发生变化㊂由文献[22]可知,SrGe 4O 9ʒMn 4+和BaGe 4O 9ʒMn 4+荧光粉的发射光谱存在明显差异,前者的发射光谱与本文基本一致,后者的发射光谱包含两个强度相当的峰位(P2和P3)㊂因此我们推断,系列样品中Sr 2+逐渐被Ba 2+取代至Sr 2+ʒBa 2+比值等于2ʒ3时,发射0.800.6Ba 2+content yN o r m a l i z e d i n t e n s i t y1.00.60.40.20（a ）0.10.20.30.40.5y =0.4Sr 1-y Ge 3.985O 9∶0.015Mn 4+,y Ba 2+600姿/nmN o r m a l i z e d i n t e n s i t y1.20.60.40.20（b ）650P11.41.00.8P4P3P2670nm 642nm EM 姿ex=275nm 655nm665nm 700750Sr 1-y Ge 3.985O 9∶0.015Mn 4+,y Ba 2+y =0.000.100.200.300.400.500.60图5㊀(a)Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0.0~0.6)荧光粉的归一化发射光谱强度变化;(b)系列样品的归一化发射光谱㊂Fig.5㊀(a)Normalized PL intensity on the Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0.0~0.6).(b)Normalizedemission spectra of the series samples.㊀第5期魏恒伟,等:Ba 2+调制SrGe 4-x O 9ʒx Mn 4+晶体结构及其发光性质647㊀峰位P2ʒP3处发射强度的比值趋近于1ʒ1,导致系列样品的发射光谱的峰形由以SrGe 4O 9ʒMn 4+为主渐变为文献中以BaGe 4O 9ʒMn 4+为主㊂为了进一步分析局部结构变化对Mn4+周围配位环境的影响,本文将SrGe 4O 9结构中的Sr1O10多面体与BaGe 4O 9结构中Ba1O10多面体的键长进行了对比,相关数据如表3所示[19,23]㊂可以看出,Sr O 键长均小于Ba O 键长,这就意味着Ba 2+进入SGOM 荧光粉的结构中后,会使Sr1O10多面体扩张形成(Sr1/Ba)O10,进而影响与之相连接的(Ge /Mn)O4和(Ge /Mn)O6多面体,使Mn4+周围的配位环境受到挤压,导致Mn4+离子间距离缩短,相互作用增加,无辐射跃迁减少,从而提高了材料的发光强度,并减少了热衰㊂表3㊀Sr1O10和Ba1O10多面体局部晶体结构(键长)的对比[19,23]Tab.3㊀Local structure of Sr1O10polyhedron compare withBa1O10polyhedron [19,23]abc Sr1O10多面体ab cBa1O10多面体名称键长/nm名称键长/nmSr1 O10.3156(9)Ba1 O10.3223(1)Sr -O20.2601(8)Ba1 O20.2708(1)Sr1 O50.2977(7)Ba1 O50.3029(7)Sr1 O40.2820(7)Ba1 O40.2896(1)Sr1 O30.2644(8)Ba1 O30.2765(4)图6是Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+系列荧光粉寿命的归一化图谱,内插图反映了样品荧光寿命随Ba 2+含量y 的变化趋势㊂样品的荧光寿命曲线可用单指数函数[24]进行拟合,方程式如下:I t =A 1exp(-t /τ),(1)其中,I t 是在时间t 对应的发光强度,A 1是常数,τ是寿命㊂计算发现Ba 2+含量y 值增加到0.6时,样品的寿命呈线性增加趋势,从1.003ms 增加到1.384ms㊂这可能是由于(Sr1/Ba)O10多面体扭曲改变Mn4+周围的局部环境,增大了跃迁几率,减少了非辐射跃迁的几率[25]所致㊂荧光粉的热稳定性是材料应用的一个重要指104t /msN o r m a l i z e d i n t e n s i t y1230.110姿ex =275nm,姿em =660nmy=0.00.10.20.30.40.50.6Sr 1-y Ge 3.985O 9∶0.015Mn 4+,y Ba 2+1.41.31.21.11.000.10.20.30.40.50.6Ba 2+content yt /m s图6㊀Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0.0~0.6)荧光粉的归一化寿命曲线和寿命-浓度变化曲线Fig.6㊀Normalized decay curves and the correlation of life-time-concentration of Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0.0-0.6)phosphor标,主要依赖于材料发光强度与温度之间的变化关系㊂图7为Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+系列化合物中y =0和y =0.4荧光粉样品发光强度随温度的变化趋势图㊂随着温度升高,SrGe 3.985O 9ʒ0.015Mn 4+和Sr 0.6Ba 0.4Ge 3.985O 9ʒ0.015Mn 4+样品的发光强度均呈下降趋势,150ħ的发光强度较室温测试强度分别衰减了24.5%和29.1%,表明两者的热稳定性良好㊂对比两者发现,Ba 2+离子的引入不仅将Sr 0.6Ba 0.4Ge 3.985O 9ʒ0.015Mn 4+样品的发光强度提高了近50%,还明显改善了其热猝灭效应,与前面通过分析表3数据得出来的结果基本一致㊂传统LED 封装主要采用 蓝光芯片+硅胶树脂+荧光粉 的方式,得到的产品存在严重的光衰㊁光色偏移㊁光密度低等问题[26]㊂为了解决这一问题, 蓝光芯片(紫外芯片)+荧光玻璃片(荧光陶瓷片) 的方式应运而生[27-30]㊂本文对得到的荧光粉进2.5×10525225T /℃I n t e n s i t y /a .u .50751001251501752002503.0×1052.0×1051.5×1051.0×1055.0×1040y =0.00.4Sr 1-y Ge 3.985O 9∶0.015Mn 4+,y Ba 2+图7㊀样品Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0,0.4)的发光强度随温度的变化Fig.7㊀PL intensity varied with temperature in the selectedsample Sr 1-y Ge 3.985O 9ʒ0.015Mn 4+,y Ba 2+(y =0,0.4)648㊀发㊀㊀光㊀㊀学㊀㊀报第42卷行玻璃化处理,制备出了厚度为0.2mm 的荧光玻璃片㊂图8是样品Sr 0.6Ge 3.985O 9ʒ0.015Mn 4+,0.4Ba 2+10090200700姿/nmT r a n s m i t t a n c e /%8070605040300400500600800UVSr 0.6Ge 3.985O 9∶0.015Mn 4+,0.4Ba2+图8㊀Sr 0.6Ge 3.985O 9ʒ0.015Mn 4+,0.4Ba 2+荧光玻璃的透射光谱Fig.8㊀Transmittance spectrum of Sr 0.6Ge 3.985O 9ʒ0.015Mn 4+,0.4Ba 2+所制备荧光玻璃的透射光谱,可以看到其在275nm 和430nm 均有吸收,这与图4(a)中的激发光谱一致㊂在550~800nm 范围内,样品的最大透光率为78.7%㊂由内插图可知,在紫外灯照射下,样品呈现红光㊂4㊀结㊀㊀论本文利用高温固相法合成了系列SrGe 4-x O 9ʒx Mn 4+(SGOM)红色荧光粉,通过向基质中引入Ba 2+调制基质的局部结构,增加了电子与声子之间的相互作用,实现了Mn 4+离子发射光谱的调控㊁发光强度的增强,并减弱了其热猝灭效应㊂将荧光粉和玻璃相结合,获得了最大透光率为78.7%㊁厚度为0.2mm 的荧光玻璃,拓展了荧光粉在白光LED 中的应用㊂参㊀考㊀文㊀献:[1]PARK K ,HEO M H ,KIM K Y ,et al ..Photoluminescence properties of nano-sized (Y 0.5Gd 0.5)PO 4ʒEu 3+phosphor pow-ders synthesized by solution combustion method [J ].Powder Technol .,2013,237:102-106.[2]SMET P F ,PARMENTIER A B ,POELMAN D.Selecting conversion phosphors for white 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