Effect of Sintering Temperature on Piezoelectric and Ferroelectric Properties of Lead-Free Piezoelectric Ta-modified (K0.5Na0.5)NbO3 Ceramics

Lead-free potassium sodium niobate ceramic, with the nominal composition of Ta-modified K0.5Na0.5NbO3, were synthesized by conventional solid state sintering, and its dielectric, ferroelectric, and piezoelectric properties were characterized as a function of sintering temperature. The orthorhombic to tetragonal phase transition (TO-T) temperature of Ta-modified (0.5% mole) K0.5Na0.5NbO3 ceramic sample for the 1100 degrees C sintering temperature was about 220 degrees C, and its Curie temperature was about 420 degrees C. The high bulk density was obtained for all compositions by solid state sintering in air. Bulk density was increased with temperature and it reached to 4.25 g/cm(3). In addition, the ferroelectric loop and dielectric characteristics dependence of different sintering temperature for Ta-modified K0.5Na0.5NbO3 ceramic sample was obtained. Finally, we found that the piezoelectric constant (d(33)) was 120 pC x N-1, remanent polarization (P-r) was 22 mu C/cm(2), and electromechanical coupling coefficients (k(P)) was about of 0.4.