Microstructures and piezoelectric properties in the Li2O-Excess 0.95(Na0.5K0.5)NbO3-0.05LiTaO3 ceramics

As a candidate for lead-free piezoelectric materials, Li2O-excess 0.95(Na0.5K0.5)NbO3-0.05LiTaO(3) (NKN-5LT) ceramics were developed by a conventional sintering process. The sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN-5LT ceramics was observed with varying Li2O content. This grain-growth behavior was explained in terms of interface reaction-controlled nucleation and growth. In the 1 mol% Li2O excess NKN-5LT samples sintered at 1000 degrees C for 4 h in air, the electromechanical coupling factor and the piezoelectric constant of NKN-5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively.