Reaction Kinetics for Lead‐Free 0.94(K _0.5 Na _0.5 )NbO ₃ –0.06LiNbO ₃ Ceramic Synthesis with Ultrasonic Irradiation

The effects of ultrasonic irradiation treatment at room temperature on the nonisothermal reaction kinetics for the formation of 0.94(K _0.5 Na _0.5 )NbO ₃ ‐0.06LiNbO ₃ (0.94 KNN –0.06 LN ) lead‐free piezoelectric ceramics were studied. It was observed that sonication dramatically decreased the sizes of the starting material aggregates and enhanced the interaction between the individual reactants even at room temperature. Through quantitative analyses on the activation energies of the decomposition of the starting alkali carbonates and formation of the resulting perovskite phase, it was found that the activation energies decreased with increasing ultrasonic power. More interestingly, the activation barrier for the decomposition of the carbonates was reduced to below the critical value for the crystallization of the perovskite phase with the high irradiation power, so that the reaction of forming the perovskite phase was not rate‐limited by the decomposition of the carbonates. This finding highlights the significance of ultrasound utility in processing KNN ‐based ceramics with reduced synthesis temperature and thus improved control of chemical stoichiometry.