Isothermal Section At 1500 Degrees C For The Ceo2-La2o3-Sm2o3 System

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 Ln(2)O(3) 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 CeO2 to a = 0.5576 nm for the three-phase (A + B + F) 50 % mol CeO2-37.5% mol La2O3-12.5% mol Sm2O3 sample along the...2-( 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- singlephase (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 CeO2-La2O3-Sm2O3 phase diagram at 1250 degrees 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 CeO2La2O3-Sm2O3 system are presented as reference material and can be used, in particular, for design and development of new materials.