Crystal structure and cation ordering in novel perovskite type oxides PrBaCoTa(Nb)O6–δ

Novel complex oxides PrBaCoNbO6–δ (PBCN) and PrBaCoTaO6–δ (PBCT) are obtained via solid state reactions. X-ray and electron diffraction data for PBCN and PBCT demonstrate cubic space symmetry (S.G. Fm–3m) of the double perovskite crystalline lattice characterized by the rock salt type ordered arrangement of Co/Nb and Co/Ta and random distribution of Pr/Ba atoms. The ab initio electronic structure calculations reveal that the disordered elementary cell is distinguished with the minimum energy. The optical measurements show that PBCN and PBCT compounds are semiconducting materials having maximum light absorption in ultraviolet (UV) region which is consistent with the computer simulations of electronic structure. The thermodynamic modeling results suggest that the structural robustness of PBCN and PBCT phases at heating may be related with large absolute values of oxygen partial enthalpies. •Various superstructures found for PrBaCoNbO6 and PrBaCoTaO6.•Low thermal expansion values for oxides studied.•High stability in measured pO2−T domain is observed.•Defect chemistry model based on DFT-calculations proposed.