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).

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

Domaines: Chimie; Cristallographie; Matériaux; Chimie théorique et/ou physique

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⟩