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单相Ce0.5Zr0.5O2立方固溶体的高压高温合成
引用本文:许大鹏,张弓木,李莉萍,苏文辉.单相Ce0.5Zr0.5O2立方固溶体的高压高温合成[J].高等学校化学学报,2001,22(4):524-530.
作者姓名:许大鹏  张弓木  李莉萍  苏文辉
作者单位:1. 吉林大学物理系;吉林大学无机合成与制备化学教育部重点实验室
2. 吉林大学物理系;吉林大学无机合成与制备化学教育部重点实验室,中国科学院国际材料物理中心,凝聚态和辐射物理分中心
基金项目:国家自然科学基金! (批准号 :198740 2 3 )资助
摘    要: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.

关 键 词:纳米晶  立方固溶体  热稳定性  氧化铈  氧化锆  合成  电学性质

Synthesis of Single-phase Cubic Ce0.5Zr0.5O2 Solid Solution under High Pressure and High Temperature
Abstract:Using nanoparticles of CeO2 and ZrO2 prepared by chemical precipition method as the starting materials, the single-phase cubic Ce0.5Zr0.5O2 solid solution has been synthesized under high pressure and high temperature for the first time. The structural characteristics and valence state of the single-phase cubic Ce0.5Zr0.5O2 solid solution were investigated by XRD, TG-DTA, Raman, XPS and EPR measurements. The XRD results showed that the nanocrystalline mixtures of CeO2-50% ZrO2 can form a cubic Ce1-xZrxO2 solid solution above 1.67 GPa and above 1 073 K, but the product is in a mixture state. The single-phase cubic Ce0.5Zr0.5O2 solid solution can be obtained only under the certain conditions of 3.1 GPa at 1 073 K. The high pressure promotes the process of the solid state reaction and the temperature of forming CeO2-ZrO2 solid solution decreases under high pressure. The DTA curve of the single-phase cubic Ce0.5Zr0.5O2 solid solution showed a broad exothermic peak between 403 K and 742 K. But the XRD pattern and Raman spectra displayed that the structure of the solid solution had not been changed before and after annealing at 773 K for 1 h. It revealed that the cubic Ce0.5Zr0.5O2 solid solution was stable in structure below 773 K. The EPR spectra recorded at room temperature gave an evidence of the presence of Ce3+ and O2- in CeO2 nanoparticles. However, the signals of Ce3+ and O2- have not been detected in Ce0.5Zr0.5O2 solid solution. An unknown signal(g=1.990) has been observed in cubic Ce0.5Zr0.5O2 solid solution which has not been changed after annealing at 773 K for 1 h, exhibiting that there exists no Ce3+ in cubic Ce0.5Zr0.5O2 solid solution and the Ce4+ has not been reduced into Ce3+ after annealing. The hyperfine structure in Zr3d XPS spectrum has been observed for the Ce0.5Zr0.5O2 solid solution. It shows that there may exist some Zr ions with a low valence-state. The ionic conductivity measured by impedance spectroscopy showed that the cubic Ce0.5Zr0.5O2 solid solution exhibits only the bulk conductivity. The bulk conductivity(σ=1.2×10-5 S/cm at 823 K, σ=2.1×10-3 S/cm at 1 123 K) is the same as that of CeO2, but smaller than that of Y2O3-stabilized ZrO2. A marked curvature at T=823 K has been observed in the Arrhenius plot of the bulk conductivity. The activation energy below 823 K is lower than that above 823 K, and the reason has been discussed.
Keywords:Cerium oxide  Zirconium oxide  Nanocrystalline  High  pressure and high  temperature  Solid solution
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