Zr1-xMxWMoO8-x/2和Zr1-xMxW2O8-x/2固溶体的晶胞参数与晶格畸变的关系

合成了Zr1-xMxWMoO8-x/2(M=Er,Tm,Yb,Sc,In,Ga,Al)和Zr1-xMxW2O8-x/2(M=Eu,Er,Yb,Sc,In,Ga,Al)2个系列的固溶体,前者具有β-ZrW2O8结构类型(简称β相);后者具有α-ZrW2O8结构类型(简称α相)。建立了相和相的晶胞参数与M3+离子浓度的Vegard方程,测定了上述固溶体的固溶度。讨论了M3+离子的化学性质与Vegard斜率SV的关系。分析了α相的SαA与β相的SβA的关系;揭示了α-Zr1-xMxW2O8-x/2晶格中2[WO4]四面体对的取向有序程度对晶格畸变的贡献。提出上述固溶体的晶胞参数随溶质浓度增加而减小,主要是由于氧空位缺陷相互作用的结果。     

Zr(WMo)1-x/2VxO8-x/2：多元素同/低价取代立方ZrW2O8结构类型热收缩固溶体的合成、结构与性质

利用酸蒸气水热法合成了Zr(WMo)1-x/2VxO7-x/2(OH)2·2H2O(x=0.04,0.08,0.10,0.14,0.20,0.22,0.26,0.32)四方晶相固溶体。以此为前驱体,通过高温脱水和相转变法合成了立方相Zr(WMo)1-x/2VxO8-x/2(x=0.04,0.08,0.10,0.14,0.20,0.22)固溶体。立方Zr(WMo)1-x/2VxO8-x/2固溶体具有Pa3空间群。Zr(WMo)1-x/2VxO8-x/2的平均晶体结构描述为按照化学计量的ZrV2O7结构与β-ZrWMoO8结构的叠加。ZrV2O7在立方ZrWMoO8中的固溶度为11mol%;立方Zr(WMo)1-x/2VxO8-x/2固溶体的相变温度低于200 K;在200 K～573 K温度范围内具有负热膨胀系数;线热膨胀系数近似为常数。     

钙长石中镓置换骨架铝对结构和Eu~(2+)发光特性的影响

采用高温固相法在弱还原气氛下制备了Ca0.955Al2-xGaxSi2O8∶Eu2+(x=0～1.0)系列荧光粉,研究了Ga3+置换Al3+对晶体结构和光谱特性的影响。Ga3+以类质同相替代CaAl2Si2O8晶格中的Al3+形成连续固溶体,晶胞参数a,b,c和晶胞体积V随Ga3+置换量呈线性增大;晶面夹角α,β和γ随Ga3+置换量的增加呈线性递减。荧光激发谱为宽带,位于230～420 nm,可拟合成4个峰,表观峰值位于352 nm;随着Ga3+置换量的增加,半高宽从112 nm减小到98 nm。发射光谱位于375～560 nm,可由421和457 nm两峰拟合而成,表观峰值位于425 nm,随着Ga3+置换量的增加,两拟合峰均线性红移,且拟合峰强度比呈线性递减。     

单相Ce0.5Zr0.5O2立方固溶体的高压高温合成

以化学沉淀法制备的 Ce O2 和 Zr O2 纳米微粒为前驱体 ,首次在高压高温 (3 .1 GPa,1 0 73 K)下合成了单相 Ce0 .5Zr0 .5O2 面心立方固溶体 .使用 X射线衍射、TG-DTA、XPS、Raman、电子自旋共振谱和交流阻抗谱等对样品的结构、Ce离子的价态和导电性进行了表征 .实验结果表明 ,纳米 Ce O2 -50 % Zr O2 混合物在高压 (0 .9GPa以上 )高温 (1 0 73 K以上 )条件下可以发生固态反应 ,高压下固溶温度明显降低 .Ce0 .5Zr0 .5O2 面心立方固溶体在 773 K以下是热稳定的 ,不发生结构转变 ,固溶体中 Ce离子完全以 Ce4 + 形式存在 ,773 K退火也不引起 Ce4 + 向 Ce3 + 转变 ,晶格中氧缺位非常少 .Ce0 .5Zr0 .5O2 面心立方固溶体是离子导电 ,82 3 K时电导率 σ=1 .2× 1 0 -5S/cm,与纯 Ce O2 在同温度下的电导率同数量级 ;1 1 2 3 K时 σ=2 .1× 1 0 -3 S/cm,小于掺入稀土或碱土氧化物的氧化锆和氧化铈基电解质的电导率 .在高温区和低温区 ln(σT)与 1 /T的关系满足斜率不同的二条直线 ,低温活化能小于高温活化能 .固溶体的显微硬度 (50 g载荷 )为 572 HV.     

钪对Al—6Mg—Zr合金焊接抗腐蚀的影响

采用中性盐雾试验和剥落腐蚀等方法研究了微量稀土元素Sc对Al—6Mg—Zr合金焊接接头耐蚀性能的影响，并用金相显微镜和透射电子显微镜观察合金焊接接头的微观组织、探讨其腐蚀机理。结果表明，添加了Sc元素后的Al—6Mg—Sc—Zr合金焊接接头比Al—6Mg—Zr合金具有更好的耐蚀性能。研究认为，添加Sc元素能有效地细化晶粒，形成的Al3(Sc，Zr)第二杷能强烈地阻止位错和亚晶界的运动，提高了合金的再结晶温度，从而使合金组织中的β(Mg5Al8，Mg2Al3)沉淀相分布均匀、呈弥散分布，最终使合金的腐蚀敏感性降低。     

Ga~(3+)对Eu~(2+)掺杂钡长石结构和发光特性的影响

在弱还原气氛下采用高温固相法制备Ba0.955A l2-xGaxS i2O8:Eu2+(x=0~1.0)系列荧光粉,研究Ga3+置换A l3+对晶体结构和光谱特性的影响。Ga3+与A l3+以类质同相替代进入BaA l2S i2O8晶格形成连续固溶体,晶胞参数a,b,c,β和晶胞体积V均随Ga3+置换量呈线性增加。宽带激发光谱,覆盖范围为230~400 nm,可拟合成4个峰,表观峰值位于330 nm,基本不随Ga3+置换量变化;随着Ga3+置换量的增加,半高宽从93 nm减小至83 nm。发射光谱位于375~560 nm,可由422和456 nm两峰拟合而成,表观峰值位于434 nm,两拟合峰峰位均随Ga3+置换量呈线性红移,且拟合峰强度比呈线性递减。     

(Gd1-xErx)2Zr2O7红外发射率对高温导热性能的影响规律研究EI北大核心CSCD

采用固相合成法制备Er2O3掺杂(Gd1-xErx)2Zr2O7(x=0,0.1,0.2)陶瓷材料，利用X射线衍射仪、激光导热仪以及傅里叶变换红外光谱仪对陶瓷材料的物相结构、热导率及高温红外发射率分别表征并对结果进行分析。结果表明，在Rad+pc模型中(Gd1-xErx)2Zr2O7陶瓷试样的热导率随掺杂量先降低后升高，总体上，Er3+的掺杂降低了Gd2Zr2O7的热导率，而Cape+pc模型中(Gd1-xErx)2Zr2O7陶瓷试样热导率首先随温度升高而逐渐降低，800℃出现拐点随温度呈增大趋势。随Er2O3掺杂量的增加，(Gd1-xErx)2Zr2O7陶瓷试样1100℃红外发射率(3～5μm)与光子热导率具有相同变化趋势，发射率的降低导致了热导率测试值的增大，这一现象与材料晶格振动相关。     

Sr_(0.955)Al_(2-x)B_xSi_2O_8∶0.025Eu~(2+)荧光粉的制备、晶体结构及发光性能（英文）

通过高温固相反应在弱还原气氛下制备了Sr_(0.955)Al_(2-x)B_xSi_2O_8∶0.025Eu~(2+)(x=0～0.9)一系列荧光粉,研究了B(Ⅲ)取代基质晶格中的Al(Ⅲ)对荧光粉晶体结构和Eu~(2+)发光性能的影响。B(Ⅲ)以类质同相取代基质晶格中Al(Ⅲ),形成了连续固溶体。随着B(Ⅲ)取代量的增加,荧光粉的晶胞参数(a、b、c)和晶胞体积(V)呈线性递减,而晶胞参数(β)呈线性递增。荧光粉的激发光谱为位于225～400nm的宽峰,表观峰值位于350 nm,激发峰的半高宽(FWHM)随着B(Ⅲ)取代量的增加,从90 nm减小到102 nm。发射光谱位于370～600 nm的宽峰,可拟合为409和447 nm两个峰,表观峰值位于409 nm。随着B(Ⅲ)取代量的增加,2个拟合峰位均出现蓝移且2个峰强度比呈线性递减。根据试样荧光光谱,通过Van Uitert经验公式计算得出SrAl_2Si_2O_8∶Eu~(2+)中Sr~(2+)的配位数为9。随着B(Ⅲ)取代Al(Ⅲ)进入基质晶格,造成发光中心Eu与配体O距离增加,使得Eu~(2+)所处的晶体场强度减小,发光中心Eu~(2+)的5d能级分裂减小,造成Eu~(2+)最低发射能级重心上移,2个拟合谱峰峰位均呈线性蓝移。     

Er3+/Yb3+共掺纳米In2O3的制备及上转换发光

用低温溶剂热法以乙二醇为溶剂合成了Er3+和Yb3+共掺的In2O3纳米晶。用X射线衍射(XRD)、透射电镜(TEM)、漫反射光谱和上转换发光光谱对样品进行了分析。XRD和TEM结果表明,产物为纯的立方相In2O3结构,粒径约为30 nm;漫反射光谱显示了In2O3∶Er3+,Yb3+纳米晶在522、653和975 nm附近有3个吸收带;在980 nm近红外光激发下,样品发射出中心波长为525及555 nm的绿光和662 nm的红光,分别对应于Er3+的2H11/2→4I15/2、4S3/2→4I15/2和4F9/2→4I15/2跃迁;研究了Er3+和Yb3+离子的不同掺杂浓度对发光强度的影响,确定了Yb3+和Er3+离子的最佳掺杂浓度均为3%;双对数曲线显示绿光和红光的发射过程均为双光子吸收过程,对样品的上转换发光机制进行了初步讨论。     

Y2O2S∶Er3+，Yb3+的制备及Er3+离子在晶场中的能级分裂

采用沉淀法制备前驱体,通过不同温度合成了上转换发光材料Y2O2S∶Er3+,Yb3+,运用XRD,SEM和上转换发射光谱对其进行表征。结果表明,所合成的Y2O2S∶Er3+Yb3+属于六方晶系晶体,随着合成温度的升高,产物的粒径不断增大,上转换发射光强度逐渐增加。研究Y2O2S∶Er3+Yb3+的上转换发光过程,红光发射和绿光发射分别源于Er3+离子的4F9/2→4I15/2以及2H11/2→4I15/2,4S3/2→4I15/2能级跃迁。利用群论计算了晶场中Er3+离子的能级分裂数目。     

Comprehensive interpretation of a substitution effect on an order-disorder phase transition in A(1-x)MxW2O(8-y) (A = Zr, Hf; M = trivalent cations) and other ZrW2O8-based solid solutions

Hf(1-x)Lu(x)W(2)O(8-y) solid solutions up to x = 0.04, based on a negative thermal expansion material HfW(2)O(8), were synthesized by a solid state reaction method. X-ray diffraction experiments of these solid solutions from 90 to 560 K indicated thermal contraction with increasing temperature. Temperatures of order-disorder phase transition (T(trs)) associated with the orientation of WO(4) tetrahedra were determined from disappearance of a characteristic diffraction peak (310). The T(trs) of the solid solutions drastically decreased with increasing Lu content. Saturated order parameters (eta(s)) associated with the orientational order of the WO(4) pairs were estimated from the characteristic diffraction peak at sufficient low temperature. These behaviors of Hf(1-x)Lu(x)W(2)O(8-y) are consistent with those of Zr(1-x)M(x)W(2)O(8-y) (M = Sc, Y, In, Lu). The drastic suppression of T(trs) in Hf(1-x)Lu(x)W(2)O(8-y) can be interpreted in the framework of a model proposed for Zr(1-x)M(x)W(2)O(8-y), which states the existence of a local nanoregion including the WO(4) pairs having the frozen-in orientational disorder. To understand the substitution effect on the order-disorder phase transition comprehensively, classification based on the saturated order parameter eta(s) of the phase transition of AW(2)O(8) (A = Hf, Zr)-based solid solutions was carried out and discussed.     

Structural characterization and oxidative dehydrogenation activity of V2O5/Ce(x)Zr(1-x)O2/SiO2 catalysts

The thermal stability of a nanosized Ce(x)Zr(1-x)O2 solid solution on a silica surface and the dispersion behavior of V2O5 over Ce(x)Zr(1-x)O2/SiO2 have been investigated using XRD, Raman spectroscopy, XPS, HREM, and BET surface area techniques. Oxidative dehydrogenation of ethylbenzene to styrene was performed as a test reaction to assess the usefulness of the VOx/Ce(x)Zr(1-x)O2/SiO2 catalyst. Ce(x)Zr(1-x)O2/SiO2 (1:1:2 mol ratio based on oxides) was synthesized through a soft-chemical route from ultrahigh dilute solutions by adopting a deposition coprecipitation technique. A theoretical monolayer equivalent to 10 wt % V2O5 was impregnated over the calcined Ce(x)Zr(1-x)O2/SiO2 sample (773 K) by an aqueous wet impregnation technique. The prepared V2O5/Ce(x)Zr(1-x)O2/SiO2 sample was subjected to thermal treatments from 773 to 1073 K. The XRD measurements indicate the presence of cubic Ce0.75Zr0.25O2 in the case of Ce(x)Zr(1-x)O2/SiO2, while cubic Ce0.5Zr0.5O2 and tetragonal Ce0.16Zr0.84O2 in the case of V2O5/Ce(x)Zr(1-x)O2/SiO2 when calcined at various temperatures. Dispersed vanadium oxide induces more incorporation of zirconium into the ceria lattice, thereby decreasing its lattice size and also accelerating the crystallization of Ce-Zr-O solid solutions at higher calcination temperatures. Further, it interacts selectively with the ceria portion of the composite oxide to form CeVO4. The RS measurements provide good evidence about the dispersed form of vanadium oxide and the CeVO4 compound. The HREM studies show the presence of small Ce-Zr-oxide particles of approximately 5 nm size over the surface of amorphous silica and corroborate with the results obtained from other techniques. The catalytic activity studies reveal the ability of vanadium oxide supported on Ce(x)Zr(1-x)O2/SiO2 to efficiently catalyze the ODH of ethylbenzene at normal atmospheric pressure. The remarkable ability of Ce(x)Zr(1-x)O2 to prevent the deactivation of supported vanadium oxide leading to stable activity in the time-on-stream experiments and high selectivity to styrene are other important observations.     

单一基质白光荧光粉Ca0.955-xAl2Si2O8:0.045Eu2+,xMn2+的晶胞参数变化和光谱特性

利用高温固相反应制备了Ca_(0.955-x)Al_2Si_2O_8∶0.045Eu~(2+),xMn~(2+)(x=0,0.05,0.10,0.15,0.20,0.25,0.30,0.325,0.35,0.375,0.40,0.425)一系列试样,系统研究了Mn~(2+)取代基质中Ca~(2+)进入晶格中对其晶胞参数和光谱特性影响。Mn~(2+)以类质同相替代Ca~(2+)进入晶体晶格中,形成了连续固溶体,试样均为三斜晶系,P空间群。随着Mn~(2+)掺杂量增加,晶胞参数(a,b,c,γ)和晶胞体积V均呈线性递减,且a轴减幅最大,b轴最小,晶面夹角(α,β)呈线性递增。在357 nm激发下,获得的Ca_(0.955-x)Al_2Si_2O_8∶0.045Eu~(2+),xMn~(2+)发射光谱均有Eu~(2+)的4f→5d跃迁产生的433 nm和Mn~(2+)的~4T_1(~4G)→~6A_1(~6S)跃迁产生的567 nm两个宽带谱组成。在荧光粉Ca_(0.955-x)Al_2Si_2O_8∶0.045Eu~(2+),xMn~(2+)中,Eu~(2+)与Mn~(2+)间存在能量传递,Eu~(2+)→Mn~(2+)间能量传递的临界距离R_(Eu-Mn)=0.947 1 nm,Eu~(2+)→Mn~(2+)能量传递过程为电四极-电四极的多极矩相互作用。通过改变Mn~(2+)掺杂量,在紫外芯片的有效激发下,荧光粉的发射光颜色可从蓝光区(0.158 2,0.086 0)逐渐移至近白光区(0.295 3,0.298 9),可获得一种紫外激发适用于白光LED的单一组分白色荧光粉。     

Solid state NMR characterization of individual compounds and solid solutions formed in Sc(2)O(3)--V(2)O(5)--Nb(2)O(5)--Ta(2)O(5) system

In this study, (51)V, (45)Sc and (93)Nb MAS NMR combined with satellite transition spectroscopy analysis were used to characterize the complex solid mixtures: VNb(9(1-x))Ta(9x)O(25), ScNb((1-x))Ta(x)O(4) and ScNb(2(1-x))Ta(2x)VO(9) (x = 0, 0.3, 0.5, 0.7, 1.0). This led us to describe the structures of Sc and V sites. The conclusions were based on accurate values for (51)V quadrupole coupling and chemical shift tensors obtained with (51)V MAS NMR/SATRAS for VNb(9)O(25), VTa(9)O(25) and ScVO(4). The (45)Sc NMR parameters have been obtained for Sc(2)O(3), ScVO(4), ScNbO(4) and ScTaO(4). On the basis of (45)Sc NMR and data available from literature, the ranges of the (45)Sc chemical shift have been established for ScO(6) and ScO(8). The gradual change of the (45)Sc and (51)V NMR parameters with x confirms the formation of solid solutions in the process of synthesis of VNb(9(1-x))Ta(9x)O(25) and ScNb((1-x))Ta(x)O(4), in contrast to ScNb(2(1-x))Ta(2x)VO(9). The cation sublattice of ScNb((1-x))Ta(x)O(4) is found to be in octahedral coordination. The V sites in VNb(9(1-x))Ta(9x)O(25) are present in the form of slightly distorted tetrahedra. The (93)Nb NMR parameters have been obtained for VNb(9)O(25).     

Interaction of Keggin anions of 12-tungstophosphoric acid with Ce(x)Zr(1-x)O2 solid solutions

The interaction of 20 wt% 12-tungstophosphoric acid with Ce(x)Zr(1-x)O(2) solid solutions has been studied by PXRD, FTIR, FT-Raman, H(2)-TPR, NH(3)-TPD, diffuse reflectance UV-vis-NIR, and (31)P MAS NMR techniques. The study indicates that the Keggin anions are attached to Lewis metal ion centres and anion vacancies on Ce(x)Zr(1-x)O(2) supports through WO terminal bonds. The Keggin units at the interface are chemically perturbed as indicated by non-intrinsic IR bands observed at 958 cm(-1) (WO(ter) bond), and 1052, 1102 cm(-1) (PO bond). NH(3)-TPD shows that the Keggin anions fixed to Lewis sites and/or oxygen ion vacancies decrease the ammonia uptake on Ce(x)Zr(1-x)O(2) solid solutions. H(2)-TPR shows modified redox behaviour of Ce(x)Zr(1-x)O(2) solid solutions due to the simultaneous reduction of ceria, decomposition of Keggin anions and the reduction of WO(3). The broadening of (31)P MAS NMR and DR-UV-vis-NIR spectra demonstrate the existence of chemical interactions between the Keggin anions and Ce(x)Zr(1-x)O(2) supports.     

氧气氛下固溶体Sn1-xZrxO2选择催化还原一氧化氮的增强效应

Reduction of NO by hydrocarbons in an oxidizing atmosphere is an attractive way to substitute the traditional NOx abatement technology from a viewpoint of practical application to the deNOx systems of diesel and lean-burn gasoline engine exhausts[1～3]. In this study, a series of novel catalysts Sn1 - xZrxO2 solid solutions were prepared by substituting some of the Sn4 + ions in a cassiterite lattice with Zr4+ ions.These solid solutions performed significantly higher activity than pure SnO2 presented on the selective reduction of NO with propene in the poresence of O2.     

SnO2基固溶体用于甲烷深度氧化：X射线衍射外推法测定 SnO2晶格容量

CH4和 CO是两种主要的温室效应气体和空气污染物,催化氧化是最有效的消除 CH4和 CO的方法.研发不含贵金属的金属氧化物催化剂或者减少催化剂中贵金属用量为该领域研究热点. SnO2是一种重要的宽禁带 n型半导体材料,广泛应用于气敏器件、锂离子电池以及光电设备. SnO2表面富含活泼的缺位氧且具有良好的热稳定性,因此其在催化方面的性能近年来逐渐受到人们关注.在过去的5年中,本团队深入研究了 SnO2材料在空气污染治理和绿色能源生产等领域的应用及其催化性质.发现通过其它阳离子如 Fe3+, Cr3+, Ta5+, Ce4+和Nb5+等的掺杂,替换晶格中部分 Sn4+,形成金红石型 SnO2固溶体结构,显著提高了催化剂氧物种的流动性、活性和催化剂本身的热稳定性.固溶体材料是一类重要的催化剂,受到广泛关注.一个典型的例子是铈锆固溶体,其作为储氧材料已广泛应用于汽车尾气净化器.形成固溶体结构后,氧化铈的储氧能力和热稳定性得到显著提高.为有效形成固溶体,两个阳离子需要具有相似的离子半径和电负性.以往,人们基于结构中金属阳离子和氧阴离子的离子半径提出了容忍因子的判别方法,以此来判断固溶体是否能有效形成及所生成固溶体的稳定性.我们在前期工作中,以 Sn-Nb固溶体为例,提出了简单的X射线衍射(XRD)外推法来计算固溶体晶格容量,即形成稳定固溶体时客体阳离子取代主体晶格阳离子的最大值.作为延续工作,本文采用共沉淀法制备了一系列 Sn/M (M = Mn, Zr, Ti, Pb)摩尔比为9/1的 SnO2基催化剂,并用于 CH4和 CO催化氧化.结果表明, Mn3+, Zr4+, Ti4+和 Pb4+均可以掺杂进四方金红石型 SnO2晶格中,形成稳定的固溶体结构.其中 Sn-Mn-O固溶体表现出最高活性.为了深入研究 Mn2O3在 SnO2中的晶格容量及最优催化剂配比,采用共沉淀法制备了一系列不同 Sn/Mn摩尔比的样品,采用 XRD, N2-BET, H2-TPR, SEM和XPS等手段对其物理化学性能进行了表征,并考察了对 CH4的催化氧化性能.通过 XRD外推法测定了 Mn3+离子在 SnO2中的晶格容量为0.135 g Mn2O3/g SnO2,相当于 Sn/Mn摩尔比为79/21.这表明形成稳定的固溶体后, SnO2晶格中最多只有21% Sn4+可以被 Mn3+替代;当 Mn3+含量超过晶格容量时,过量的 Mn3+在催化剂表面形成 Mn2O3,对催化剂活性不利.类似于 Sn-Nb-O固溶体,在 Sn-Mn-O催化剂体系中亦观察到明显的晶格容量效应.纯相的 Sn-Mn-O固溶体比含过量 Mn2O3晶相的 Sn-Mn-O催化剂具有更高活性.     

Doping of Ceria-Zirconia Solid Solution with Rare-earth Elements

The increasingly restrictive regulations on car exhaust emissions will necessitate the development of a new generation of three way catalysts (TWC) with better performance1. Ceria (CeO2) is the main component of the current TWC: its key role is to compensate the fluctuations in the exhaust stream composition, therefore, allowing to expand the air/fuel(A/F) operating window of catalytic converters2. This property is related to its oxygen storage capacity (OSC), associated to the redox couple Ce4+/Ce3+. However, CeO2 alone is easy to sinter to lost OSC at high temperature3.Ceria-zirconia (CexZr1-xO2) solid solutions by incorporation of Zr4+ in the CeO2 lattice have enhanced OSC and greater thermal stability, which are becoming the key materials for the new generation of TWC4. OSC of ceria-zirconia solid solutions can be further improved by the addition of M3+ dopants5. Besides Ce, other rare-earth elements such as Pr and Tb can vary their oxidation state. Pr and Tb are particularly suitable for making solid solutions with cerium because the known structure of PrO2 and TbO2 is of the cubic fluorite type, and the ionic radii of Pr4+ and Tb4+ are close to that of Ce4+6.In this paper, Ce0.6Zr0.3M0.1O2 (M=Y, La, Pr, Tb) were prepared by co-precipitation technique and characterized by a series of methods. Meanwhile, palladium-only TWCs were prepared by slurry coating and their catalytic activity was evaluated under the condition of simulated exhaust in the lab.XRD and FT-Raman spectra results show Ce0.6Zr0.3M0.1O2 have cubic fluorite structure which keep unchanging at high temperature. The different dopant ion radii brought different effect on the cell parameter of Ce0.6Zr0.3M0.1O2. The X-ray photoelectron spectroscopy (XPS) results show that the binding energy of Ce3d, Zr3d and O1s for Ce0.6Zr0.3M0.1O2 rose compared with that for Ce0.6Zr0.4O2, indicating dopant elements changed chemistry environment of solid solutions which was available to improve redox performance From TPR results, doping La can not change redox performance of solid solution, but doping Y decreased reduction temperature. Doping Pr and Tb notably improved redox performance of solid solutions due to appearance of low-temperature reduction peak in TPR profile which come from mobility of bulk oxygen.Compared with Pd/Ce0.6Zr0.4O2, doping Y and La unchanged A/F characteristic of TWCs, but doping Pr and Tb widen A/ F operating window and make HC, CO and NO have higher conversion.The light-off temperature of Pd/Ce0.6Zr0.3La0.1O2 was corresponded to that of Pd/Ce0.6Zr0.4O2.However, the light-off temperatures of Pd/Ce0.6Zr0.3M0.1O2 (M=Y, Pr, Tb) were lower than that of Pd/Ce0.6Zr0.4O2, which kept much lower after high temperature treatments. Among Pd/Ce0.6Zr0.3M0.1O2 (M=Y, La, Pr, Tb), Pd/Ce0.6Zr0.3Tb0.1O2 showed wider A/F operating window,higher conversion, lower light-off temperature and better high-temperature resistance     

Influence of disorder-to-order transition on lattice thermal expansion and oxide ion conductivity in (Ca(x)Gd(1-x))(2)(Zr(1-x)M(x))2O7 pyrochlore solid solutions

The effect of simultaneous substitutions of Ca at A site and Nb or Ta at B site in pyrochlore-type solid solutions: (Ca(x)Gd(1-x))(2)(Zr(1-x)M(x))(2)O(7) (x = 0.1, 0.2, 0.3, 0.4, 0.5 and M = Nb or Ta) were studied by powder X-ray diffraction (XRD), FT NIR Raman spectroscopic techniques and transmission electron microscopy. The solid solutions were prepared by the conventional high-temperature ceramic route. The XRD results and Rietveld analysis revealed that the defect fluorite structure of Gd(2)Zr(2)O(7) progressively changed to a more ordered pyrochlore phase by simultaneous substitutions at A and B sites. Raman spectroscopy reveals the progressive ordering in the anion sublattice with simultaneous doping. High-resolution images and selected-area electron diffraction patterns obtained from TEM confirms the XRD and Raman spectroscopic results. High-temperature XRD studies show that the lattice expansion coefficient in these pyrochlore oxides is of the order of 10(-6) K(-1). Lattice thermal expansion coefficient increases with increase of disorder in pyrochlore oxides, and hence the variation of thermal expansion coefficient with composition is also a good indicator of disordering in pyrochlore-type oxides. The ionic conducting properties of the samples were characterised by impedance spectroscopy, and it was found that Nb-doped compositions show a considerable change in conductivity near the phase boundary of disordered pyrochlore and defect fluorite phases.