V2O5/CaO diffusion couples were prepared to investigate the reaction characteristics between V2O5 and CaO at 1073 K to 1273 K in air. The distribution, species, and number of phases generated in the proximity of the V2O5/CaO interface were characterized by electron probe microanalysis (EPMA), Fourier transform–infrared (FT–IR) spectroscopy, and X-ray diffraction (XRD) that was capable of selecting the scanning location. The results show that CaV2O6 was quickly generated to become the matrix all over the V-rich layer at a relatively low temperature (1073 K to 1223 K); Ca2V2O7 was then formed in the vicinity of the CaV2O6/CaO interface. The presence of Ca2V2O7 near the CaV2O6/air interface was unexpected and indicated that the diffusion of oxygen from the air into the V-rich layer had promoted its formation. Upon increasing the annealing temperature, CaV2O6 disappeared gradually at 1223 K, Ca2V2O7 became the matrix at 1223 K, and Ca3(VO4)2 appeared near the Ca2V2O7/CaO interface at 1173 K. Average interdiffusion coefficients in Ca3(VO4)2 at 1173 K, 1223 K, and 1273 K were 1.66 × 10−10, 3.45 × 10−10, and 17.5 × 10−10 cm2 s−1, respectively. The diffusion activation energy calculated using the Arrhenius equation was 290.15 ± 32.29 kJ/mol. With increasing annealing time, the amount of the phases (Ca2V2O7 at 1073 K to 1123 K and Ca3(VO4)2 at 1173 K to 1273 K) in the vicinity of the V-rich layer/CaO interface increased. At 1173 K, the diffusion thickness of Ca3(VO4)2 increased with increasing annealing time with a square root of time dependency, which suggested that the formation of Ca3(VO4)2 in the Ca2V2O7 mixture was governed by the solid–solid diffusion process.

中文翻译：

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V2O5/CaO 界面附近不同位置生成的钒酸钙随退火参数的演变

制备 V2O5/CaO 扩散偶以研究 V2O5 和 CaO 在 1073 K 至 1273 K 空气中的反应特性。通过电子探针微量分析 (EPMA)、傅里叶变换红外 (FT-IR) 光谱和 X 射线衍射 (XRD) 表征在 V2O5/CaO 界面附近产生的相的分布、种类和数量。能够选择扫描位置。结果表明，CaV2O6 在相对较低的温度（1073 K 至 1223 K）下迅速生成，成为遍布富钒层的基体；然后在 CaV2O6/CaO 界面附近形成 Ca2V2O7。CaV2O6/空气界面附近Ca2V2O7 的存在是出乎意料的，这表明氧气从空气扩散到富钒层促进了其形成。随着退火温度的升高，CaV2O6 在 1223 K 时逐渐消失，Ca2V2O7 在 1223 K 时成为基质，Ca3(VO4)2 在 1173 K 时出现在 Ca2V2O7/CaO 界面附近。 Ca3(VO4)2 在 1173 K、1223 K 和 1273 时的平均互扩散系数K 分别为 1.66 × 10−10、3.45 × 10−10 和 17.5 × 10−10 cm2 s−1。使用阿伦尼乌斯方程计算的扩散活化能为 290.15 ± 32.29 kJ/mol。随着退火时间的增加，富钒层/CaO 界面附近的相（1073 K 至 1123 K 的 Ca2V2O7 和 1173 K 至 1273 K 的 Ca3(VO4)2）的数量增加。在 1173 K 时，Ca3(VO4)2 的扩散厚度随着退火时间的增加而增加，且具有时间依赖性的平方根，这表明 Ca2V2O7 混合物中 Ca3(VO4)2 的形成受固-固扩散过程控制.