Study of the solubility of La3+–Dy3+ defect complexes and dielectric properties of (Ba1−xLax)(Ti1−xDyx)O3 ceramics

Abstract

Based on the double-site compensation mode, the solubility of LaBa•–DyTi′ defect complexes and the dielectric properties of (Ba1−xLax)(Ti1−xDyx)O3 (0.03≤x≤0.20) ceramics (BLTD) were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, electron paramagnetic resonance (EPR), and dielectric measurements. The solid solubility of LaBa•–DyTi′ defect complexes in the BaTiO3 lattice was determined to be x=0.17. With an increase in x, the increase in the unit cell volume was linear and satisfied Vegard׳s law. The dielectric-peak temperature (Tm) decreased rapidly at a rate of −23°C/at% LaBa•–DyTi′. The BLTD ceramics with x=0.05 and 0.07 met the Y5V specification with a higher room-temperature permittivity (εRT′~4000 and ~3000) and a lower dielectric loss (tanδ<0.04). A weak g=2.004 EPR signal associated with ionized Ti-vacancy defects appeared in all of the BLTD ceramics. The exclusive occupations of La3+ ions at Ba sites and the preference for the self-compensation mode by Dy3+ ions are responsible for the formation of predominant LaBa•–DyTi′ defect complexes and the appearance of the minute concentration of Ti vacancies and DyBa•–DyTi′ defect complexes.