Energetics of Cerium?Zirconium Substitution in the xCe<sub>0.8</sub>Y<sub>0.2</sub>O<sub>1.9</sub>?(1?x)Zr<sub>0.8</sub>Y<sub>0.2</sub>O<sub>1.9</sub>System
作者:Weiqun Chen、Alexandra Navrotsky、Yue Ping Xiong、Harumi Yokokawa
DOI:10.1111/j.1551-2916.2006.01427.x
日期:2007.2
Energetics of Ce–Zr substitution in xCe0.8Y0.2O1.9−(1−x)Zr0.8Y0.2O1.9 (0≤x≤1) solid solutions, potential candidates for electrolytes in solid oxide fuel cells, were investigated by high temperature oxide melt drop solution calorimetry. The enthalpies of formation relative to the solid solution end‐members, Ce0.8Y0.2O1.9 and Zr0.8Y0.2O1.9 (ΔHf,ss), are slightly positive. The whole substitution range can be divided into three regimes: a zirconia‐dominated region (0≤x<0.4), where ΔHf,ss increases from 0 to 3.9 kJ/mol; a ceria‐dominated region (0.6<x≤1), where ΔHf,ss remains nearly constant at 0 to 0.7 kJ/mol; and a transitional region (0.4≤x≤0.6), where ΔHf,ss decreases from 3.9 to 0.7 kJ/mol. Such a trend in ΔHf,ss strongly supports a scavenging effect of Zr4+ on oxygen vacancies, i.e. oxygen vacancies prefer the nearest neighboring sites of Zr4+ as in yttria‐stabilized zirconia. The formation enthalpy from binary oxides, fluorite CeO2, monoclinic ZrO2 and C‐type YO1.5, (ΔHf,ox) is also slightly positive, varying analogously to ΔHf,ss.
铈–锆固溶体Ce0.8Y0.2O1.9−(1−x)Zr0.8Y0.2O1.9(0 ≤ x ≤ 1)的热力学性质,作为潜在的固体氧化物燃料电池电解质候选材料,通过高温氧化物熔融滴液溶液量热法进行了研究。相对于固溶体端成员,Ce0.8Y0.2O1.9和Zr0.8Y0.2O1.9的生成焓(ΔHf,ss)略微为正。整个取代范围可以分为三个区域:氧化锆占主导的区域(0 ≤ x < 0.4),其中ΔHf,ss从0增加到3.9 kJ/mol;氧化铈占主导的区域(0.6 < x ≤ 1),其中ΔHf,ss保持在0到0.7 kJ/mol之间几乎恒定;以及过渡区域(0.4 ≤ x ≤ 0.6),其中ΔHf,ss从3.9 kJ/mol下降到0.7 kJ/mol。这种ΔHf,ss的变化趋势有力地支持了Zr4+对氧空位的“清除效应”,即氧空位更倾向于邻近Zr4+的最近邻位置,类似于氧化钇稳定氧化锆。从二元氧化物(氟化物型CeO2、单斜锆石型ZrO2和C型YO1.5)的生成焓(ΔHf,ox)也是略微为正,并且类似于ΔHf,ss的变化。