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

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>_x</i> Na_1-<i>x</i> )NbO₃ single crystals with an ultrahigh large-signal piezoelectric coefficient <i>d</i> ₃₃* of 9000 pm V^-1, which is superior to the highest value reported in state-of-the-art lead-based single crystals (~2500 pm V^-1). 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.