Defect structure-electrical property relationship in Mn-doped calcium strontium titanate dielectric ceramics
Ca0.6Sr0.4TiO3 (CST) ceramics with different amounts of Mn dopant (0-2.0 mol%) were prepared by solid-state reaction method. The electric field and temperature stability of energy storage performance was found to be greatly enhanced with moderate doped level of 0.5 mol%. The dielectric loss-frequency spectra revealed the existence and evolution of defect dipoles at elevated temperature, which was confirmed directly by electron paramagnetic resonance (EPR) spectra. The response of defect dipoles was characterized by thermally stimulated depolarization current (TSDC), where the activation energy and the concentration evolution of defect dipoles were calculated, with the highest values observed for 0.5% doped samples. The dissociation of defect dipoles and the movement of free VO·· were analyzed by high-temperature impedance spectra analysis, with the activation energy of 1.04-1.60 eV, and 0.5% doped samples also demonstrated the highest Ea. The relationship between microscopic defect structure and macroscopic electrical behavior was established in this work.