Phase equilibria and structural transformations in the ternary ZrO2–La2O3–Gd2O3 system at 1600°C were studied by X-ray diffraction, microstructural, and electron microprobe analyses over the entire composition range. Fields of solid solutions based on the cubic fluorite-type (F) and tetragonal (T) modifications of ZrO2, monoclinic (M) and cubic (C) modifications of Gd2O3, hexagonal (A) modification of La2O3, and an ordered intermediate phase with La2Zr2O7 pyrochloretype structure (Py) exist in the system. The boundaries of phase fields and lattice parameters of the phases were determined. In the ZrO2-rich corner, solid solutions based on the ZrO2 tetragonal modification are formed. The solubility of La2O3 in the T-ZrO2 lattice is low and reaches ~0.5 mol.%, which is evidenced by X-ray diffraction and microstructural analyses. The solid solutions based on the tetragonal modification of zirconia cannot be quenched when cooled with the furnace. The diffraction patterns recorded at room temperature include peaks of the M-ZrO2 monoclinic phase. The ordered Ln2Zr2O7 pyrochlore-type (Py) phase is in equilibrium with all phases (except for C-Gd2O3) existing in the ternary ZrO2–La2O3–Gd2O3 system at 1600°C and forms substitutional solid solutions with phases of the binary systems. The greatest solubility in the Ln2Zr2O7 (Py) lattice is shown by Gd2O3 along the Gd2O3–(67 mol.% ZrO2–33 mol.% La2O3) section. The La2Zr2O7 (Py) lattice parameters change from a = 1.0781 nm for the single-phase (Py) sample containing 67 mol.% ZrO2–33 mol.% La2O3–0 mol.% Gd2O3 to a = 1.0741 nm for the threephase (F + Py + B) sample containing 43.55 mol.% ZrO2–21.45 mol.% La2O3–35 mol.% Gd2O3 along the Gd2O3–(67 mol.% ZrO2–33 mol.% La2O3) section. The cubic phases are primarily in equilibrium in the ZrO2–La2O3–Gd2O3 system: F-Fm3m, Py-Fd3m, and C-Ia3. The isothermal section of the ZrO2–La2O3–Gd2O3 phase diagram at 1600°C contains four three-phase regions (T + F + Py, A + Py + B, Py + F + B, and F + C + B) and nine two-phase regions (T + Py, F + Py, F + T, F + C, F + B, B + Py, A + Py, B + A, and B + C).

中文翻译：

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ZrO2-La2O3-Gd2O3 体系中 1600°C 的相平衡

通过 X 射线衍射、显微结构和电子探针分析在整个组成范围内研究了 1600°C 下三元 ZrO2-La2O3-Gd2O3 系统中的相平衡和结构转变。基于 ZrO2 的立方萤石型 (F) 和四方 (T) 变体、Gd2O3 的单斜 (M) 和立方 (C) 变体、La2O3 的六方 (A) 变体和有序中间相的固溶体场体系中存在 La2Zr2O7 烧绿石型结构（Py）。确定了相场的边界和相的晶格参数。在富含 ZrO2 的角部，形成基于 ZrO2 四方变体的固溶体。La2O3 在 T-ZrO2 晶格中的溶解度很低，达到 ~0.5 mol.%，X 射线衍射和显微结构分析证明了这一点。基于氧化锆四方改性的固溶体在炉冷时不能淬火。在室温下记录的衍射图案包括 M-ZrO2 单斜相的峰。有序的 Ln2Zr2O7 烧绿石型 (Py) 相与三元 ZrO2–La2O3–Gd2O3 系统中存在的所有相（C-Gd2O3 除外）在 1600°C 处于平衡状态，并与二元系统的相形成置换固溶体。Ln2Zr2O7 (Py) 晶格中的最大溶解度由 Gd2O3 沿着 Gd2O3–(67 mol.% ZrO2–33 mol.% La2O3) 部分显示。La2Zr2O7 (Py) 晶格参数从含有 67 mol.% ZrO2–33 mol.% La2O3–0 mol.% Gd2O3 的单相 (Py) 样品的 a = 1.0781 nm 变为三相 (F + Py + B) 样品含有 43.55 mol.% ZrO2–21.45 mol.% La2O3–35 mol. 沿 Gd2O3–(67 mol.% ZrO2–33 mol.% La2O3) 部分的 Gd2O3 百分比。立方相主要在 ZrO2-La2O3-Gd2O3 系统中处于平衡状态：F-Fm3m、Py-Fd3m 和 C-Ia3。ZrO2–La2O3–Gd2O3 相图在 1600°C 的等温截面包含四个三相区域（T + F + Py、A + Py + B、Py + F + B 和 F + C + B）和九个两相区域（T + Py、F + Py、F + T、F + C、F + B、B + Py、A + Py、B + A 和 B + C）。