Microstructure and piezoelectric properties of (Na_0.85K_0.15)_0.5 Bi_0.5TiO₃ lead-free ceramics prepared by tape casting processing

(Na_0.85K_0.15)_0.5 Bi_0.5TiO₃ lead-free piezoelectric ceramics were prepared by tape casting process. The effects of heat-treatment on the microstructure and piezoelectric properties of ceramics were investigated. The results show that the ceramics with densified microstructure can be prepared by tape casting process. The microstructure of cross section is not the same dense as that of surface. There are two phases coexist in the ceramics: perovskite phase and K₂Ti₆O₁₃ phase whose appearance is whisker shape. It is difficult to eliminate K₂Ti₆O₁₃ by heat-treatment process. But heat-treatment will improve the microstructure of cross section effectively and decrease piezoelectric constant d₃₃, dielectric constant and ε dielectric loss tanδ. (Na_0.85K_0.15)_0.5 Bi_0.5TiO₃ (lead-free piezoelectric ceramics show obvious characteristic of ferroelectrics with coercive electric field E_c 2680 V/mm and remnant polarization P_r 36.6 μC/cm², d₃₃, K_p and Q_m of ceramics are 113 pC/N, 0.27 and 154 respectively.