Preparation and crystal structure of new perovskite-type
cobaltites R1-xR'xCoO3
Chem.
Met. Alloys 3
(2010) 184-190
https://doi.org/10.30970/cma3.0165
O. MYAKUSH, V. BEREZOVETS, A. SENYSHYN, L. VASYLECHKO
The crystal structures of new ternary oxides R1‑xR'xCoO3 (R, R'=La,
Pr, Nd, Sm), obtained by
solid-state reaction in air at 1200ºC, have been studied by X-ray powder
diffraction, using conventional laboratory and synchrotron radiation sources.
It was established that at ambient conditions La1‑xPrxCoO3 (x ≤ 0.2) and La1‑xNdxCoO3 (x ≤ 0.1) display a rhombohedral perovskite structure
isotypic with NdAlO3 (space group R‑3c). For La1‑xPrxCoO3 (x ≥ 0.6), La1‑xNdxCoO3 (x ≥ 0.5), Pr1‑xNdxCoO3, Pr1‑xSmxCoO3, and Nd1‑xSmxCoO3 the orthorhombic GdFeO3 type
of structure (space group Pbnm) is inherent. The obtained structural data indicate the
existence of a continuous solid solution with orthorhombic perovskite
structure in the PrCoO3–NdCoO3 system and possible
formation of such solid solutions in the PrCoO3–SmCoO3 and
NdCoO3–SmCoO3 systems. Two types of solid solution with rhombohedral and orthorhombic perovskite
structures with an immiscibility gap between them have been confirmed in the
LaCoO3–PrCoO3 and LaCoO3–NdCoO3
systems. The ranges of existence of these solid solutions have been determined.
Projection of the unit cell and packing of CoO6 octahedra in the structures of La0.9Nd0.1CoO3 (left) and Pr0.8Sm0.2CoO3 (right)
Keywords
Cobaltites / Crystal structure / X-ray powder
diffraction / Perovskite