INTERACTION OF CERIUM, LANTHANUM AND SAMARIUM OXIDES AT 1250 °С

 
O.Andrijevska 1,
  
V.S. Urbanovich 2,
 
S.V. Yushkevych 1,
 
L.S. Spasonova 3
 

1 I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
2 Scientific-Practical Materials Research Centre of NAS of Belarus, 19 P. Brovki st., Minsk, 22007, Byelorus
3 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 37, Prosp. Peremohy, Kiev, 03056, Ukraine
kornienkooksana@ukr.net

Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2021, #01/02
http://www.materials.kiev.ua/article/3197

Abstract

Materials produced from cerium oxides stabilized by rare-earth metal (REM) oxides are promising for medical and engineering applications for their unique properties. The СеO2–La2O3–Ln2O3 phase diagrams serve as a physicochemical basis for developing solid electrolytes for fuel cells, oxygen sensors, catalyst carriers, protective coatings on alloys, etc. Phase equilibria and structural transformations in the СeO2–La2O3–Sm2O3 system at 1250 ºС were studied by X-ray diffraction over the entire composition range. The studies found fields of solid solutions based on the cubic (F) fluorite-type modification of CeО2, monoclinic (В) and cubic (С) modifications of Sm2O3 and hexagonal (А) modification of La2O3 in the ternary СеO2–La2O3–Sm2O3 system. The phase boundaries and lattice parameters of the phases were determined. The CeО2–La2O3–Sm2O3 system at 1250 °С had predominantly cubic phases in equilibrium: CeО2-based F-phase with Fm3m space group and Sm2O3-based C-phase with Ia3 space group. The lattice parameters of the fluorite-type (F-CeO2) cubic solid solutions changed from a = 0.5409 nm for pure СеО2 to а = 0.5515 nm for the two-phase (F + C) 55 CeО2–22.5 La2O3–22.5 Sm2O3 sample (mol.%) along the La2O3 : Sm2O3 = 1 : 1 section, to а = 0.5548 nm for the two-phase 55 CeО2–33.75 La2O3–11.25 Sm2O3 sample along the La2O3 : Sm2O3 = 3 : 1 section, and to а = 0.5478 nm for the two-phase (F + C) 60 CeО2–10 La2O3–30 Sm2O3 sample along the La2O3 : Sm2O3 = 1 : 3 section. At 1250 °С, the cubic fluorite type F-CeO2 solid solutions are in equilibrium with all phases formed in the system. 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.


FUNCTIONAL MATERIALS, LATTICE PARAMETERS OF THE UNIT CELLS, PHASE EQUILIBRIA, SOLID SOLUTIONS, STATE DIAGRAM