Temperature-dependent electron paramagnetic resonance detect oxygen vacancy defects and Cr valence of tetragonal Ba(Ti<inf>1−</inf><inf>x</inf>Cr<inf>x</inf>)O<inf>3</inf> ceramics

Abstract

Temperature-dependent electron paramagnetic resonance (EPR) study was employed to detect oxygen vacancy defects in the tetragonal Ba(Ti1−xCrx)O3 (x = 5%) ceramic for the first time. In the rhombohedral phase below −150 °C, an EPR signal at g = 1.955 appeared in the insulating Ba(Ti1−xCrx)O3 (x = 5%) ceramic with an electrical resistivity of 108 Ω cm and was assigned to ionized oxygen vacancy defects. Ba(Ti1−xCrx)O3 ceramics exhibited a tetragonal structure except Ba(Ti1−xCrx)O3 (x = 10%) with a tetragonal-hexagonal mixed phase and a first-order phase transition dielectric behavior (ε′m > 11,000). Mixed valence Cr ions could coexist in ceramics, form CrTi′–VO[rad][rad] or CrTi[rad]–TiTi′ defect complexes and make no contribution to a dielectric peak shift towards low temperature.