Fabrication of Textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Electrostrictive Ceramics by Templated Grain Growth Using NaNbO3 Templates and Characterization of Their Electrical Properties

Abstract

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO(3)-0.25SrTiO(3), by using templated grain growth. Textured ceramics were prepared with 1 similar to 9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 degrees C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, S-max/E-max (d(33)*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q(33) increased from 0.017 m(4)C(-2) for untextured ceramics to 0.043 m(4)C(-2) for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO(3)-0.25SrTiO(3) composition suitable for high-precision actuation applications. Dielectric properties measured between -193 degrees C and 550 degrees C distinguished the depolarization, Curie-Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the "two" law exhibiting a temperature dependence double the value of the Curie-Weiss constant, with shifts of about 10 degrees C per frequency decade where the non-dispersive THz limit was identified.