Properties of 0.74BiNaTiO<inf>3</inf>-0.06SrTiO<inf>3</inf> / Bi<inf>0.5</inf>(Na<inf>0.8</inf>K<inf>0.2</inf>)<inf>0.5</inf>TiO<inf>3</inf> ceramic composite

Abstract

We investigated the temperature- and frequency-dependent polarization and strain of two Bismuth-based perovskite composites. A matrix material was chosen as 0.74Bi _0.5 Na _0.5 TiO ₃ -0.26SrTiO ₃ (BNT-ST) which have a transition point of 60°C from relaxor to ferroelectric phase (T _R-F ). An inclusion material was Bi _0.5 (Na _0.8 K _0.2 ) _0.5 TiO ₃ (BNKT) possessing the T _R-F of 120°C. Depending on test temperature, the different polarization and strain behaviors were observed in BN-TST/BNKT composite. At T=25°C, the composite exhibited double-like polarization loop and parabolic strain curves which involve ergodic relaxor-to-normal ferroelectric phase transition with external electric field and the reverse ferroelectric-to relaxor phase transition with removal of the field. When T= 80°C, the BNT-ST/BNKT has very slim polarization and strain of which magnitude are slightly increased values from pure BNT-BT. When T= 120°C, both composites have slim polarization and strain behaviors of which values are almost same as the pure BNT-ST. These high field-induced polarization and strain with respect to temperature for the composites are related to the thermal stability of ferroelectric inclusions, and their nucleation and growth in relaxor matrix.