Dielectric, piezoelectric, and elastic properties of K0.8Na0.2NbO3 single crystals

Abstract

A high-quality and large-sized K_0.8Na_0.2NbO₃ single crystal was successfully grown using the top-seeded solution growth method (TSSG). The temperature dependence of the dielectric during the cooling and heating of [001]_C- and [011]_C-oriented K_0.8Na_0.2NbO₃ single crystals was investigated. In order to better understand the crystal's piezoelectric properties, the complete and consistent set of dielectric, piezoelectric, and elastic constants of the [001]_C-poled K_0.8Na_0.2NbO₃ single crystal was measured for the first time, using ultrasonic and resonance methods. A large elastic stiffness constant value of c^E₁₁ = 27.4 × 10¹⁰ N m⁻² was obtained; this provides the crystal with harder transverse mechanical adaptability in the [100]_C direction. The [001]_C-poled K_0.8Na_0.2NbO₃ single crystal also exhibited high electromechanical coupling coefficients (k₁₅ = 0.448, k_t = 0.67). In addition, a comparison between the calculated and measured material constants confirmed that the orientation effect primarily contributes to the characteristics of the crystal.