Visualizing sintering process and electrical properties of SnO2 doped K0.48Na0.52NbO3 piezoelectric ceramics

In this study, the conventional solid-state sintering of lead-free (1-x)K0.48Na0.52NbO3-xSnO2 piezoelectric green bodies was analysed using thermal imaging and longitudinal/transverse shrinking. The phase structure, fracture morphology, densification, permittivity, ferroelectricity, piezoelectricity, and domain-switching activation en-ergy were investigated with increasing SnO2 content (x). Sn4+ first occupied the A site in the ABO3 structure and then substituted the B site with increasing x. This resulted in various contents of defect dipoles and oxygen vacancies, which were mainly responsible for the different ferroelectricity and piezoelectricity values. The permittivity and domain-switching activation energy were significantly affected by the local compositional disorder or fluctuation. Moreover, the influences of phase, densification, fine grain size, and domain wall on the electrical properties are also discussed. The optimum electrical properties, with Pr = 34.7 mu C/cm2, d33 = 294 pC/ N, and TC = 337 degrees C were determined for x = 0.30 mol%. This study provides a specific explanation and reference for the various electrical properties of lead-free piezoelectric ceramics.