The phase equilibria in the La2O3-Yb2O3 system were investigated using differential thermal analysis, and the phase transformations temperatures were verified. Microstructure investigation using scanning electron microscopy confirmed the presence of eutectoid reactions in the system. The heat capacity of LaYbO3 with a perovskite structure was measured in the temperature range from 250 to 1250 K using differential scanning calorimetry. The experimental results of the present work as well as reliable literature data were used to derive a thermodynamic description of the La2O3-Yb2O3 system. Isothermal sections of the ZrO2-La2O3-Yb2O3 system were constructed based on x-ray and microstructural investigations. The tie-lines change from Pyrochlore + $${\text{Yb}}_{2} {\text{O}}_{3} \_{\text{C}}$$ to $${\text{LaYbO}}_{3} \_{\text{Perovskite}}$$ + Fluorite was explained by a solid-state reaction occurring in the range between 1673 and 1873 K. The heat effect observed at 1858 K using DTA confirms the phase transformation, and its temperature was established more precisely at 1808 ± 15 K using stepwise heat treatment.

中文翻译：

---

ZrO2-La2O3-Yb2O3体系中相关系的实验研究

使用差热分析研究了 La2O3-Yb2O3 体系中的相平衡，并验证了相变温度。使用扫描电子显微镜进行的微观结构研究证实了系统中存在共析反应。使用差示扫描量热法在 250 至 1250 K 的温度范围内测量了具有钙钛矿结构的 LaYbO3 的热容量。本工作的实验结果以及可靠的文献数据用于推导出 La2O3-Yb2O3 系统的热力学描述。ZrO2-La2O3-Yb2O3 系统的等温截面是基于 X 射线和显微结构研究构建的。