Influence of ball milling on sintering behavior and electrical properties of (Li,Na,K)NbO3 lead-free piezoceramics

Volatilization of alkali elements during sintering process is one of the major factors influencing the processing stability of lead-free (Na,K)NbO3 (KNN) piezoceramics. With a purpose to reduce sintering temperature by refining particle sizes, an extensive ball-milling step was intentionally introduced to the fabrication process of KNN-based ceramics with a nominal composition of Li0.058(Na0.52K0.48)0.942NbO3 by a solid-state powder synthesis and normal sintering method. It was revealed that prolonging the period for milling calcined powders before sintering process significantly reduced the particle sizes and hence sintering temperature. As a result, sintering at a reduced temperature of 1,025 °C resulted in a highly dense material with good piezoelectric and ferroelectric properties with converse piezoelectric coefficient d* 33 and remnant polarization P r reaching 266 pm/V and 15.7 μC/cm2, respectively. This study provided a facile and effective method to enhance the piezoelectric properties in KNN-based ceramics with an optimized composition by reducing the particle sizes.