ESR investigation of transition metal defects in KNbO₃

Abstract

Using ESR, the authors identified Fe3+ in the rhombohedral phase of the photorefractive compound KNbO3. Fe3+-Vo was found in the orthorhombic as well as the rhombohedral phases. The spectra were analysed and compared to those of Fe3+ and Fe3+-Vo in other oxide compounds, e.g. BaTiO3. A superposition model analysis yielded information on the geometry of Fe3+ and its nearest neighbours. Also Co2+, Co2+-Vo and Ir4+ were identified, analysed and compared to corresponding findings in other oxide hosts.