Structural position and oxidation state of nickel in SrTiO3

TL;DR

This study investigates the structural position and oxidation state of nickel in SrTiO3 using X-ray techniques, revealing stable phases, nickel substitution behavior, and implications for solar energy applications.

Contribution

It provides detailed insights into nickel's oxidation states and lattice positions in SrTiO3, highlighting the potential for solar energy conversion.

Findings

Nickel substitutes for titanium in SrTiO3 and is on-center.

Nickel's oxidation state is 2+ in NiTiO3 and close to 4+ in SrTi1-xNixO3.

Tetravalent nickel enhances light absorption in doped samples.

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 SrTi1-xNixO3 solid solution and the NiTiO3 phase are the most stable phases which can coexist. According to the EXAFS data, in the single-phase sample of SrTi0.97Ni0.03O3, 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 NiTiO3 is 2+, and in the SrTi1-xNixO3 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 SrTi1-xNixO3 solid solution. This doping seems the most promising one for solar energy converters that exploit the bulk photovoltaic effect.