Microstructure and suppressed thermal depolarisation behaviours of lead-free Na 0.5 Bi 0.5 TiO 3 :ZnO ferroelectric composite ceramics

Abstract

A 0–3 type 0.8Na_0.5Bi_0.5TiO₃(BNT):0.2ZnO lead-free ferroelectric composite ceramic structure was prepared by a solid-state oxide route. The X-ray diffraction analysis and scanning electron microscopy observation indicate that ZnO grains were scattered in the matrix consisting of BNT grains to form a (0–3) type composite structure, and a third phase Zn₂TiO₄ was formed due to the reaction ability of nano-sized ZnO with NBT compositions. The temperature-dependent electrical responses show that the dielectric anomaly at around 200°C inherited from NBT itself was suppressed as ZnO is composited, and the P_r of the specimen sintered at 1000°C keeps almost unchanged as the poling temperature is 175°C, while its retained piezoelectric strain d₃₃ value maintains 77% of the initial as exposed to 125°C annealing. These results suggest that the thermal depolarisation of BNT is suppressed due to the introduction of ZnO, even though the third phase Zn₂TiO₄ exists.