Microwave-assisted synthesis and sintering of potassium sodium niobate lead-free piezoelectric ceramics

Synthesis and sintering of (K,Na)NbO3 lead-free piezoelectric ceramics (KNN) were carried out using conventional and microwave heating processes. Microwave calcination resulted in the formation of single-phase orthorhombic perovskite structure by heating up to 950 °C. Characterization of synthesized powders with FTIR, XRD and DSC techniques revealed that without soaking time and in spite of the very short heating time in microwave, the powder calcined at 950 °C has all physical properties similar to powder synthesized in conventional furnace at the same temperature with a step by step heating regime. The bulk density of 93.8 %, piezoelectric charge coefficient (d33) of 85 pC/N and remnant polarization (Pr) of 18 µC/cm2 were achieved for sample sintered in microwave furnace at 1115 °C. These values are satisfactorily comparable with corresponding values of conventional sintering. Results showed that the microwave heating is a promising method in calcination, synthesis and sintering of potassium sodium niobate lead-free piezoelectric ceramics.