Temperature-dependent electron paramagnetic resonance detect oxygen vacancy defects and Cr valence of tetragonal Ba(Ti1-xCrx)O3 ceramics

Temperature-dependent electron paramagnetic resonance (EPR) study was employed to detect oxygen vacancy defects in the tetragonal Ba(Ti1-xCrx)O-3 (x = 5%) ceramic for the first time. In the rhombohedral phase below -150 degrees C, an EPR signal at g = 1.955 appeared in the insulating Ba(Ti1-xCrx)O-3 (x = 5%) ceramic with an electrical resistivity of 10(8) Omega cm and was assigned to ionized oxygen vacancy defects. Ba(Ti1-xCrx)O-3 ceramics exhibited a tetragonal structure except Ba(Ti1-xCrx)O-3 (x = 10%) with a tetragonal-hexagonal mixed phase and a first-order phase transition dielectric behavior (epsilon'(m) > 11,000). Mixed valence Cr ions could coexist in ceramics, form Cr-Ti'-V-O(center dot center dot) or Cr-Ti(center dot)-Ti-Ti' defect complexes and make no contribution to a dielectric peak shift towards low temperature. (C) 2017 The Authors. Published by Elsevier B.V.