Cold sintering assisted two-step sintering of potassium sodium niobate (KNN) ceramics

Potassium sodium niobate (KNN) ceramics were densified using a multiple-stage sintering process in which initially applied cold sintering process (CSP) was followed by the solid-state sintering between 1100 and 1120 degrees C. Comparative assessments demonstrated that multi-step sintered samples yielded better properties than conventionally sintering ones. The highest relative density (94.7%) and the best electrical properties were obtained from the sample subjected to cold sintering at 120 degrees C/1 h using 5 wt% deionized water subsequently heat treated at 1120 degrees C/2 h, resulting in a monolithic KNN ceramic having a piezoelectric coefficient of 120 pC/N.