Processing and optimization of textured (Na0.5Bi0.5)TiO3-BaTiO3-SrTiO3 incipient piezoelectric ceramics by Templated Grain Growth using NaNbO3 templates

Abstract

Due to their large electric field-induced strains, (Na0.5Bi0.5)TiO3 (NBT)-based lead-free piezoceramics show promise to replace lead-containing piezoelectric materials in actuator applications. However, they have some disadvantages such as large strain hysteresis and a requirement for high electric driving fields. The combined effects of chemical modification and crystallographic orientation in specific directions are effective strategies for overcoming the drawbacks of NBT-based ceramics. Chemical modification of NBT-BaTiO3 by the addition of SrTiO3 can transform it into an incipient piezoelectric, characterized by large electric field-induced strains but accompanied by significant hysteresis. To overcome this limitation, in the present work strain hysteresis is reduced by enhancing ergodicity and boosting the electrostrictive effect through the incorporation of NaNbO3 templates. At the same time, maximum strain is improved by inducing {001} crystallographic orientation via the Templated Grain Growth (TGG) method. The combination of {001} crystallographic orientation with enhanced ergodicity has improved unipolar strain (S-uni = 0.203%) and electrostrictive coefficient (Q(33) = 0.0288 m(4)/C-2) while significantly reducing strain hysteresis (H = 21.6%) at an electric field of 3.5 kV/mm in the 3 wt% NaNbO3 textured sample, compared to an untextured counterpart (S-uni = 0.13%, Q(33) = 0.0136 m(4)/C-2 and H = 47.2%). These results demonstrate that combining Templated Grain Growth with increased ergodic and electrostrictive behavior is an effective approach to reduce hysteresis while enhancing strain.