High Piezoelectric d 33 Coefficient in Li/Ta/Sb‐Codoped Lead‐Free (Na,K)NbO 3 Ceramics Sintered at Optimal Temperature

Lead‐free Li‐doped (Na,K)NbO 3 ceramics with codopants of Ta and Sb with a nominal composition of [(Na 0.535 K 0.480 ) 0.942 Li 0.058 ](Nb 0.86 Ta 0.10 Sb 0.04 )O 3 were prepared by normal sintering. The microstructure and piezoelectric, ferroelectric, and dielectric properties were investigated, with a special emphasis on the influence of sintering temperature from 1070° to 1100°C. All samples showed a pure pervoskite phase with tetragonal symmetry. The microstructure became denser but the volatilization of Na and K became intense on increasing the sintering temperature. Despite the absence of MPB‐like transitional behavior, the piezoelectric coefficient ( d 33 ), electromechanical coupling coefficient ( k p ), and dielectric constant (ɛ) showed peak values of 264 pC/N, 35.6%, and 689.4, respectively, which were obtained in the sample sintered at 1090°C, and its Curie temperature ( T C ) was about 338°C. An even higher d 33 value can be expected if the MPB‐like transitional composition range is further determined by compensating the Na and K contents.