Synthesis and Characterization of Piezoelectric (Bi_1/2Na_1/2)TiO₃ Films by a Hydrothermal Method

Abstract

Thin films of lead-free piezoelectric ceramics (Bi_1/2Na_1/2)TiO₃ (abbreviated as BNT) were prepared on pure titanium substrates by a hydrothermal method. The properties of BNT films synthesized from the reaction solution with various contents of bismuth and titanium were investigated using SEM, EDX, XRD and other instruments. Moreover, the effects of the concentrations of starting materials on permittivity and piezoelectric effect of deposited BNT films were discussed. The results showed that an impurity of Bi₂O₃ crystal was produced on the surfaces of all deposited films. With assumption of deposited films as an system of (1-x) (Bi_1/2Na_1/2)TiO₃-xBi₂O₃, the BNT content was calculated from the Bi/Ti ratio of the EDX results. The optimized synthesis condition was determined on the evaluation target of the calculated BNT content. In addition, the unimorph cantilever type actuators were fabricated by BNT deposited samples, and their piezoelectric responses were measured at their resonance frequencies under AC field. It was noted that the piezoelectric effect of the deposited BNT film was greatly dependent on its crystallization level.