Improvement of piezoelectric and ferroelectric properties in (K,Na)NbO3- based ceramics via microwave sintering

In this study modified KNN-based piezoceramics with different amounts of SrTiO3 were prepared. Sintering was carried out in a conventional furnace (via single-step as well as two-step sintering) and in a microwave furnace. Sintering behavior, piezoelectric properties, ferroelectric and strain behavior of sintered samples were investigated. Observation of microstructures proved that two-step sintering suppressed grain growth and enhanced densification. Microwave sintered samples exhibited the highest piezoelectric constant compared to the other samples which might be attributed to higher density and lower loss of volatile elements such as K and Na during microwave sintering. Microwave sintering also resulted in the improvement of ferroelectric behavior and enhancement of electric-field-induced strain. This work demonstrates the potential of microwave sintering to fabricate KNN-based ceramics with better electromechanical properties compared to those obtained using conventional furnace sintering.