Variations in the phase composition, specific surface area, and morphology of structural components in the ultrafine powder of composition (wt.%) 70 (90 ZrO2 (3 Y2O3, 2 CeO2)–10 Al2O3)–30 CoAl2O4 (70ZA30CoA), produced by hydrothermal synthesis combined with mechanical mixing, were studied in the heat treatment process up to 1300°C. The study employed Xray diffraction, scanning and transmission electron microscopy, petrography, and BET. The formation of CoAl2O4 in the 70ZA30CoA powder in the heat treatment process was accompanied by reversible phase transformations: T-ZrO2 → M-ZrO2 → T-ZrO2. The M-ZrO2 content increased from 15% to 46% in the temperature range 850–1000°C and decreased to 13% after heat treatment to 1150°C. The process involved slight coarsening of the primary T-ZrO2 particles, while the size of the primary M-ZrO2 particles remained practically unchanged. The phase transformation was due to a decrease in the free energy of the ultrafine 70ZA30CoA powder, representing a thermodynamically nonequilibrium system. The phase composition changed color of the 70ZA30CoA powder in the following sequence: gray → gray blue → dark cyan → bright blue. Morphological analysis of the structural components showed that the CoAl2O4 formation and reversible T-ZrO2 → M-ZrO2 phase transformation were accompanied by shape change, loosening, and subsequent sintering of the agglomerates. The chain-like agglomerates of various shapes and sizes indicate that the 70ZA30CoA powder sinters actively at 1300°C. The decrease in the specific surface area from 46 to 1 m2/g depending on the heat treatment temperature was determined by the development of three structural transformation processes: formation of CoAl2O4, phase transition of the ZrO2 solid solution, and sintering of the 70ZA30CoA powder. The established regularities are of fundamental importance for the microstructural design of ZrO2 composites such as ZrO2–Y2O3–CeO2–Al2O3–CoO materials of blue and other colors for various applied purposes.

中文翻译：

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热处理对超细 ZrO2–Y2O3–CeO2–Al2O3–CoO 粉末理化性质的影响

组成为 (wt.%) 70 (90 ZrO2 (3 Y2O3, 2 CeO2)–10 Al2O3)–30 CoAl2O4 (70ZA30CoA) 的超细粉末的相组成、比表面积和结构成分的形态变化，由水热合成与机械混合相结合，在高达 1300°C 的热处理过程中进行了研究。该研究采用 X 射线衍射、扫描和透射电子显微镜、岩相学和 BET。在热处理过程中，70ZA30CoA 粉末中 CoAl2O4 的形成伴随着可逆的相变：T-ZrO2 → M-ZrO2 → T-ZrO2。M-ZrO2 含量在 850-1000°C 温度范围内从 15% 增加到 46%，热处理至 1150°C 后减少到 13%。该过程涉及初级 T-ZrO2 颗粒的轻微粗化，而原始 M-ZrO2 颗粒的尺寸实际上保持不变。相变是由于超细 70ZA30CoA 粉末的自由能降低，代表了热力学非平衡系统。70ZA30CoA粉末的相组成按以下顺序改变颜色：灰色→灰蓝色→深青色→亮蓝色。结构成分的形貌分析表明，CoAl2O4 的形成和可逆的 T-ZrO2 → M-ZrO2 相变伴随着团块的形状变化、松散和随后的烧结。各种形状和尺寸的链状团块表明 70ZA30CoA 粉末在 1300°C 下烧结活跃。取决于热处理温度，比表面积从 46 减少到 1 m2/g 取决于三个结构转变过程的发展：CoAl2O4 的形成、ZrO2 固溶体的相变和 70ZA30CoA 粉末的烧结。已建立的规律对于 ZrO2 复合材料的微观结构设计至关重要，例如用于各种应用目的的蓝色和其他颜色的 ZrO2-Y2O3-CeO2-Al2O3-CoO 材料。