• Oksana A. Korniienko I. Frantsevich Institute for Problems of Materials Science, Ukraine
  • Oleksandr И. Быков I. Frantsevich Institute for Problems of Materials Science, NAS of Ukraine, Ukraine
  • Anatoliy V. Sameliuk I. Frantsevich Institute for Problems of Materials Science, NAS of Ukraine, Ukraine
  • Hanna K. Barshchevskaya I. Frantsevich Institute for Problems of Materials Science, Ukraine



phase equilibria, phase diagram, solid solution, lattice parameters, functional ceramics


Based on the studied phase equilibria, it is established that in these systems substitution-type solid solutions are formed on the basis of various crystalline modifications of the initial components. In the CeO2–La2O3–Sm2O3 system solid solutions based on cubic (F) with a fluorite-type structure of CeO2 modification, monoclinic (B), cubic (C), hexagonal (A) modifications of Ln2O3 are formed. The phase boundaries and lattice parameters of the phases were determined. It is established that the parameters of the F-CeO2 unit cell increase with the content of Ln3+. The regularities observed for the parameters of the elementary cells are based on the competition of two factors, including the average ionic radius and the repulsion of the boundaries of the same charged ions in the crystal lattice as a result of substitution. The lattice parameters of the fluorite-type (F-CeO2) cubic solid solutions changed from a = 0.5409 nm for pure СеО2 to а = 0.5576 nm for the three-phase (A + B + F) 50 % mol CeО2–37.5% mol La2O3–12.5% mol Sm2O3 sample along the СеО2–(75 % mol La2O3–25 %  mol Sm2O3) section. The length of the F-phase is determined by RDX of samples of the following compositions: 60 mol % CeO2–20 mol % La2O3–20 mol % Sm2O3,  55 mol % CeO2–33.75 mol % La2O3–11.25 mol % Sm2O3, 65 mol % CeO2–8.75 mol % La2O3–26.25 mol % Sm2O3- single-phase (F), 55 mol % CeO2–22.5 mol % La2O3–22.5 mol % Sm2O3,  60 mol % CeO2–10 mol % La2O3–30 mol % Sm2O3- two-phase (F + C) and 50 mol % CeO2–37.5 mol % La2O3–12.5 mol % Sm2O3- three-phase (A + F + B).  The isothermal section of the CeО2–La2O3–Sm2O3 phase diagram at 1250 °C contains two three-phase (A + F + B, F +B + C) and five two-phase (A + F, A + B, F + B, B + C, F + C) regions. The results of the study of phase equilibria in the ternary CeO2–La2O3–Sm2O3 system are presented as reference material and can be used, in particular, for design and development of new materials.

Author Biography

Oksana A. Korniienko, I. Frantsevich Institute for Problems of Materials Science

старший науковий співробітник


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Physical and inorganic chemistry