Dielectric properties and exploration of self-compensation mode of Tb in BaTiO3 ceramics

The self-compensation mode and dielectric properties of the nominal (Ba1-xTbx)(Ti1-xTbx)O-3 (0.05 <= x <= 0.20) ceramics (BTTT) were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-dependent Raman spectroscopy and electron paramagnetic resonance (EPR), dielectric and electrical measurements. The solid solution limit of Tb in BTTT was determined to be x = 0.12 by XRD. The variation in unit cell volume (V-0) with x satisfied Vegard's law. In the case of Ba/Ti = 1, a complete self-compensation mode of Tb3+ in BaTiO3 could not be formed like Eu3+ or Dy3+ because Tb ions in BTTT coexisted in the mixed-valence states of Ba-site Tb3+ and Ti-site Tb4+. The room-temperature resistivity decreased with increasing x owing to a gradually enhanced Tb3+ donor effect. An X5S specification with medium dielectric stability was achieved at x = 0.05. This ceramic is a promising dielectric for a higher room temperature permittivity (epsilon'(RT) = 1190), a very low dielectric loss (tan delta < 0.02), and a nearly invariant epsilon' in the frequency range of 10(2) to 10(5) Hz. (C) 2016 The Ceramic Society of Japan. All rights reserved.