Phase equilibria, crystal structure and properties of complex oxides in the Nd2O3-SrO-CoO system

T. V. Aksenova (1) , T. G. Efimova (1) , O. I. Lebedev (2) , Sh. I. Elkalashy (1) , A. S. Urusova (1) , V. A. Cherepanov (1)

1 UrFU - Ural Federal University [Ekaterinburg]
2 CRISMAT - Laboratoire de cristallographie et sciences des matériaux

The phase equilibria in the 1/2Nd(2)O(3)-SrO-CoO system were systematically studied at 1373 K in air. The intermediate phases formed in the 1/2Nd(2)O(3)-SrO-CoO system at 1373 K in air are Nd1-xSrxCoO3-delta (0.0 <= x <= 0.5 with orthorhombic structure, sp. gr. Pbnm and 0.6 <= x <= 0.95 whose structure was detected as cubic according to XRD sp. gr. Pm3m, but shown to be tetragonal by TEM due to the oxygen vacancy ordering), Nd2-ySryCoO4-delta (0.6 <= y <= 1.1 with tetragonal K2NiF4-type structure, sp. gr. I4/mmm) and Nd2-zSrzO3 (0.0 <= z <= 0.15 with hexagonal structure, sp. gr. P-3m1). The unit cell parameters for the single phase samples were refined by the Rietveld analysis. The changes of oxygen content in Nd1-xSrxCoO3-delta (0.6 <= x <= 0.95) and Ruddlesden-Popper oxide Nd2-ySryCoO4-delta were examined by TGA. All were found to be oxygen deficient phases. High-temperature dilatometry allows calculating the thermal expansion coefficient and evaluating the chemical expansion coefficient at high temperature. The projection of isothermal-isobaric phase diagram for the Nd-Sr-Co-O system at 1373 K in air to the compositional triangle of metallic components has been constructed. The phase equilibria in the studied Nd-Sr-Co-O system were compared to La-Sr-Co-O and Nd-M-Co-O (M=Ca and Ba).

Keywords: Phase equilibria; Solid solutions; Crystal structure; Oxygen nonstoichiometry; Oxygen vacancy ordering; Thermal expansion

Domains: Chemical Sciences; Cristallography; Material chemistry; Theoretical and/or physical chemistry

T. V. Aksenova, T. G. Efimova, O. I. Lebedev, Sh. I. Elkalashy, A. S. Urusova, et al.. Phase equilibria, crystal structure and properties of complex oxides in the Nd2O3-SrO-CoO system. Journal of Solid State Chemistry, 2017, 248, pp.183-191. ⟨10.1016/j.jssc.2017.02.002⟩. ⟨hal-02175433⟩