Lead-free piezoelectric ceramics manufactured from tantalum-substituted potassium sodium niobate nanopowders

Nanopowders of lead-free (K0.5Na0.5)(Nb0.9Ta0.1)O3 (KNNT) system were prepared by high-energy ball milling at different milling times keeping the milling speed fixed at 250 rpm. The particle size first decreases from 35 nm to 3 nm and then increases to 98 nm as the milling time increases in steps of 5 h from 10 h to 30 h. Without using any sintering aid, dense ceramics were formed by sintering the powders at 1050 °C for 1 h. With decreasing particle size of the starting nanopowders, the ceramics exhibit gradual increase in density from 93.1% to 95.8%, coercive field (Ec) from 10.9 kV/cm to 15.1 kV/cm, electromechanical coupling factor (kp) from 35% to 48%, and piezoelectric charge constant (d33) from 80 pC/N to 128 pC/N. The systematic changes observed in these parameters corroborate the observed increase in particle size as the milling time increases from 25 h to 30 h.