An Experimental and Theoretical Study of Ni Impurity Centers in [Ba.sub.0.8][Sr.sub.0.2]Ti[O.sub.3]

• 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: Springer 01.08.2017
• Subjects: Analysis; Perovskite
• ISSN: 1063-7834; 1090-6460
• DOI: 10.1134/S106378341708025X

The local environment and the charge state of a nickel impurity in cubic [Ba.sub.0.8][Sr.sub.0.2]Ti[O.sub.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.sup.2+] ions are in a high-spin state at the B sites of the perovskite structure and the difference of charges of [Ni.sup.2+] and [Ti.sup.4+] is mainly compensated by distant oxygen vacancies. In addition, a considerable amount of nickel in the sample is in a second phase BaNi[O.sub.3-[delta]]. 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.sup.4+] ions at the B site.