An experimental and theoretical study of Ni impurity centers in Ba0.8Sr0.2TiO3

• Published in: Physics of the solid state Vol. 59; no. 8; pp. 1512 - 1519
• Main Authors: Sluchinskaya, I. A., Lebedev, A. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.08.2017; Springer Nature B.V
• Subjects: Dielectrics; Lattice vacancies; Nickel; Perovskite structure; Physics; Physics and Astronomy; Solid State Physics; Spectroscopic analysis; Spectrum analysis; Unit cell
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S106378341708025X

The local environment and the charge state of a nickel impurity in cubic Ba 0.8 Sr 0.2 TiO 3 are studied by XAFS spectroscopy. According to the XANES data, the mean Ni charge state is ~2.5+. An analysis of the EXAFS spectra and their comparison with the results of first-principle calculations of the defect geometry suggest that Ni 2+ ions are in a high-spin state at the B sites of the perovskite structure and the difference of charges of Ni 2+ and Ti 4+ is mainly compensated by distant oxygen vacancies. In addition, a considerable amount of nickel in the sample is in a second phase BaNiO 3 − δ . The measurements of the lattice parameter show a decrease in the unit cell volume upon doping, which can indicate the existence of a small amount of Ni 4+ ions at the B site.