Analysis of Charge Compensation Mechanisms in Pr1-xAxCoO3-δ (A = Ca, Sr) by X-ray Absorption Near-Edge Structure

Abstract

The charge compensation mechanisms in polycrystalline Pr1-xCaxCoO3-δ and Pr1-xSrxCoO3-δ here synthesized by the solid-state reaction method have been investigated by analyzing the Pr-L3 and Co-K X-ray absorption near-edge structure (XANES) with the aid of first-principles calculations. The valence states of Pr ions in these materials were determined to be trivalent (Pr3+) and independent of the concentration of alkaline-earth ions observed in the Pr-L3 XANES profile. The Co-K XANES spectra shifted to the higher-energy side with an increase in alkaline-earth concentration and were examined in detail by first-principles calculations. Using calculated XANES results, we successfully determined that the valence state of Co ions is an intermediate value between 3+ and 4+ and increases with an increase in the concentration of alkaline-earth ions in Pr1-xAxCoO3-δ (A = Ca, Sr) accompanying oxygen vacancy.