Effect of sintering condition on the microstructure and electrical properties of lead-free (Na_0.5K_0.5)NbO₃ - Bi_0.5(Na_0.83K_0.17)_0.5TiO₃ ceramics

¹ Department of Electronic Engineering, Nan-Jeon University, Tainan City 737, Taiwan
² Graduate School of Engineering Science and Technology, Nan-Jeon University, Tainan City 737, Taiwan

^a Corresponding author : wangch@mail.nju.edu.tw

Abstract

In this work, the piezoelectric ceramic system of the (1-x)(Na_0.5K_0.5)NbO₃ - xBi(Na_0.83K_0.17)TiO₃ with composition close to the morphotropic phase boundary is studied. (Na_0.5K_0.5)NbO₃ with 0∼5 mole% Bi(Na_0.83K_0.17)TiO₃ has been prepared following the conventional mixed oxide process. The effect of sintering time on the properties of 0.97(Na_0.5K_0.5)NbO₃-0.03Bi(Na_0.83K_0.17)TiO₃ ceramics is discussed. For 0.97(Na_0.5K_0.5)NbO₃-0.03Bi(Na_0.83K_0.17)TiO₃ ceramics, the electromechanical coupling coefficients of the thickness mode kt and the piezoelectric constant d₃₃ reach 0.46 and 155 p/CN, respectively, at the sintering of 1100 °C for 3 h. Dielectric and piezoelectric properties have maximum values at the sintering temperature of 1100 °C for 5 h. For 0.97(Na_0.5K_0.5)NbO₃ -0.03Bi(Na_0.83K_0.17)TiO₃ ceramics, the electromechanical coupling coefficients of the thickness mode kt and the piezoelectric constant d₃₃ reach 0.56 and 190, respectively, at the sintering of 1100 °C for 5 h. The effect of prolonging the sintering time to the 0.97(Na_0.5K_0.5)NbO₃-0.03Bi(Na_0.83K_0.17)TiO₃ system is a helpful method on ceramic processing to improve densification and properties.