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

• Published in: Crystals (Basel) Vol. 14; no. 10; p. 861
• Main Authors: Andleeb, Kiran, Trung, Doan Thanh, Fisher, John G., Tran, Tran Thi Huyen, Lee, Jong-Sook, Choi, Woo-Jin, Jo, Wook
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-10-2024
• Subjects: (Na0.5Bi0.5)TiO3; Actuation; Ceramics; Composition; Curie temperature; Depolarization; Dielectric properties; Electric fields; Electrical properties; Electrostriction; electrostrictive materials; Ethanol; Grain growth; Hysteresis loops; inverse piezoelectric properties; Lead content; Lead free; Phase transitions; Raw materials; relaxor; Room temperature; Single crystals; Sodium compounds; Solid solutions; Temperature dependence; templated grain growth; Texturing; Weiss field; United States > US
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst14100861

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)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °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, Smax/Emax (d33*), 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 Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °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 °C per frequency decade where the non-dispersive THz limit was identified.