Ultra-large electric field-induced strain in potassium sodium niobate crystals.

Hu, Chengpeng; Meng, Xiangda; Zhang, Mao-Hua; Tian, Hao; Daniels, John E; Tan, Peng; Huang, Fei; Li, Li et al. · Sci Adv · 2020

basic_science · Level V

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Abstract

Electromechanical coupling in piezoelectric materials allows direct conversion of electrical energy into mechanical energy and vice versa. Here, we demonstrate lead-free (K <i><sub>x</sub></i> Na<sub>1-<i>x</i></sub> )NbO<sub>3</sub> single crystals with an ultrahigh large-signal piezoelectric coefficient <i>d</i> <sub>33</sub>* of 9000 pm V<sup>-1</sup>, which is superior to the highest value reported in state-of-the-art lead-based single crystals (~2500 pm V<sup>-1</sup>). The enhanced electromechanical properties in our crystals are realized by an engineered compositional gradient in the as-grown crystal, allowing notable reversible non-180° domain wall motion. Moreover, our crystals exhibit temperature-insensitive strain performance within the temperature range of 25°C to 125°C. The enhanced temperature stability of the response also allows the materials to be used in a wider range of applications that exceed the temperature limits of current lead-based piezoelectric crystals.