Structural position and oxidation state of nickel in SrTiO3

Abstract

The properties of Ni -doped strontium titanate are studied using X-ray diffraction and XAFS spectroscopy. It is shown that regardless of the preparation conditions, the SrTi 1-x Ni x O 3 solid solution and the NiTiO 3 phase are the most stable phases which can coexist. According to the EXAFS data, in the single-phase sample of SrTi 0.97 Ni 0.03 O 3, the Ni atoms substitute for the Ti ones and are on-center. The distortion of the oxygen octahedra is not observed. The XANES spectra analysis shows that the oxidation state of nickel in NiTiO 3 is 2+, and in the SrTi 1-x Ni x O 3 solid solution it is close to 4+. It is shown that the strongest light absorption in doped samples is associated with the presence of tetravalent nickel in the SrTi 1-x Ni x O 3 solid solution. This doping seems the most promising one for solar energy converters that exploit the bulk photovoltaic effect.