Giant Strains in Non-Textured (Bi1/2Na1/2)TiO3-Based Lead-Free Ceramics
Recent intense research on lead-free piezoceramics has led to the discovery of many oxide ceramics with excellent properties.[1-4] Among reported solid solution families, the bismuth-alkali titanate-based system develops the largest strain under applied electric field (0.45%–0.48%),[5-7] making it a promising material for applications in actuators.[8, 9] However, high electric fields are required in this system, resulting in a low d33* (the large-signal piezoelectric coefficient). Values of d33* greater than 1000 pm V−1 were reported in barium titanate- and alkali-niobate-based families, but the achievable electrostrain is quite low (often below 0.3%).[10-12] Single crystals possess remarkable values for both d33* and electrostrain,[13, 14] the difficulties in fabrication and associated high cost have yet to be overcome for production in quantity. In this Communication, we report giant electrostrain (0.70%) and d33* (1400 pm V−1) in a non-textured lead-free polycrystalline ceramic. These excellent properties are attributed to electric-field-induced phase transitions, according to in situ transmission electron microscopy (TEM) examinations. The results are directly beneficial to next-generation actuators, and may also shed light on the development of deformable structural ceramics.