Phase equilibria and structural transformations in the La₂O₃–Y₂O₃–Gd₂O₃ system at 1600°C were studied by X-ray diffraction, electron microscopy, and petrography in the entire composition range. Fields of solid solutions based on hexagonal (A) modification of La₂O₃, cubic (C) modification of Y₂O₃, and monoclinic (B) modification of La₂O₃ (Gd₂O₃) were identified in the system. The starting materials were La₂O₃, Gd₂O₃, and Y₂O₃ (99.99%) powders. Samples were prepared with concentration steps of 1–5 mol.%. Weighed portions of the oxides were dissolved in HNO₃ (1 : 1) solutions. This was followed by evaporation of the solutions and decomposition of the nitrates at 800°C for 2 h. The samples were heat-treated in three stages: 1100°C (168 h), 1500°C (70 h), and 1600°C (10 h) in air in furnaces with FeCrAl (H23U5T) and molybdenum disilicide (MoSi₂) heating elements. X-ray diffraction analysis was carried out using the powder method with a DRON-3 diffractometer at room temperature (Cu-K_α radiation). The scanning step was 0.05–0.1° at angles 2θ = 15–90°. The isothermal section of the La₂O₃–Y₂O₃–Gd₂O₃ phase diagrams at 1600°C was characterized by three single-phase (A-La₂O₃, B-La₂O₃ (Gd₂O₃), C-Y₂O₃) and two two-phase (A + B, B + C) regions. The solubility limits were determined, and composition dependences of the lattice parameters for the phases formed in the system were plotted. No ordered perovskite-type phase was found in the system at 1600°C. A continuous series of solid solutions based on the monoclinic modification of B-La₂O₃(Gd₂O₃) formed in the system and occupied the largest area of the isothermal section. Yttrium oxide stabilized the total mutual solubility of lanthanum and gadolinium oxides. With the addition of heavier ions, the lattice parameters of the B modification reduced and the lattice volume and, accordingly, density increased. The lattice of solid solutions based on the B modification of rare-earth metal oxides became more densely packed with a higher concentration of yttrium oxide.

通过 X 射线衍射、电子显微镜和岩相学研究了整个成分范围内La ₂ O ₃ -Y ₂ O ₃ -Gd ₂ O _{3体系在 1600°C 下的相平衡和结构转变。}系统中识别出了基于La ₂ O ₃的六方(A)变体、Y ₂ O ₃的立方(C)变体和La ₂ O ₃ (Gd ₂ O ₃ )的单斜(B)变体的固溶体场。起始材料为La ₂ O ₃、Gd ₂ O ₃和Y ₂ O ₃ (99.99％)粉末。样品的制备浓度为 1–5 mol.%。将称重部分的氧化物溶解在HNO ₃ (1:1)溶液中。随后蒸发溶液并在 800°C 下分解硝酸盐 2 小时。样品分三个阶段进行热处理：1100°C（168 小时）、1500°C（70 小时）和 1600°C（10 小时），在炉中空气中使用 FeCrAl (H23U5T) 和二硅化钼 (MoSi ₂ )加热元件。X射线衍射分析采用粉末法，使用DRON-3衍射仪在室温下进行（Cu-K _α辐射）。扫描步长为 0.05–0.1°，角度 2θ = 15–90°。1600℃时La ₂ O ₃ –Y ₂ O ₃ –Gd ₂ O ₃相图的等温段表现为三个单相(A-La ₂ O ₃ , B-La ₂ O ₃ (Gd ₂ O ₃ )、CY ₂ O ₃ )和两个两相(A + B、B + C)区域。确定了溶解度极限，并绘制了系统中形成的相的晶格参数的组成依赖性。在 1600°C 的系统中没有发现有序的钙钛矿型相。基于 B-La ₂ O ₃ (Gd ₂ O _{3)单斜晶系改性的连续系列固溶体}）在系统中形成并占据等温截面的最大面积。氧化钇稳定了氧化镧和氧化钆的总互溶度。随着较重离子的添加​​，B 改性的晶格参数降低，晶格体积以及相应的密度增加。基于稀土金属氧化物 B 改性的固溶体晶格变得更加致密，氧化钇浓度更高。