Pairing High Piezoelectric Coefficients, d33, with High Curie Temperature (TC) in Lead-Free (K,Na)NbO3.
The largest piezoelectric properties, d33= 416 pC/N and 490 pC/N, in KxNa1-xNbO3ceramics have been reported for compositions close to polymorphic phase transition (PPT); however, they also have Curie temperatures, TC, of around 217-304 °C, considerably lower than those of undoped KNN ceramics (420 °C). High d33along with high TCremains the ideal choice for applications but, unfortunately, not attained up to now. Here, we show that using KNN single crystals as seeds for template grain growth (TGG) of KNN ceramics enables dramatic improvements in the electromechanical properties while maintaining a high TC. The (001)-oriented (K0.5Na0.5)0.98Li0.02NbO3ceramics engineered by TGG using (K0.5Na0.5)NbO3crystals as templates exhibit a high d33of 280 pC/N while maintaining the high TCof 430 °C. Enhanced piezoelectricity is attributed to long-range ordered ferroelectric domain patterns consisting of 90° and 180° domains, similar to single crystals. It is the first time that pairing high d33and high TCin KNN, keeping a high PPT temperature, is achieved. This study is an unequivocal proof that it is possible to maximize d33, keeping a high TCin KNN without resorting to heavily doped compositions. This work opens the door to high-performance, rare-earth free, compositionally simple lead-free and low-cost electromechanical compounds, which can largely expand lead-free piezoelectrics applications.
Department of Materials and Ceramic Engineering, CICECO Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
Muhammad Asif
MA
Rafiq
Department of Materials and Ceramic Engineering, CICECO Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
Maria Elisabete
ME
Costa
Department of Materials and Ceramic Engineering, CICECO Aveiro Institute of Materials, University of Aveiro , 3810-193 Aveiro, Portugal.
Paula Maria
PM
Vilarinho
ferroelectrics; lead-free; piezoelectrics; potassium sodium niobate; single crystals; template grain growth; textured ceramics