A systematic study on the microstructure, dielectric, ferroelectric and electrostriction properties of KNN modified BNT-BT ceramics across a wide composition range

A series of (1-x)(0.94BNT-0.06BT)-xKNN ceramics across a wide composition range (x = 0–36 mol.%) was successfully fabricated. Systematic investigation reveals that KNN content significantly influences the phase structure and functional properties, including dielectric, ferroelectric, and electrostrictive behaviors. These composition-dependent characteristics are highly related to the evolution of polar nanoregions (PNRs), particularly the R3c and P4bm phases. The (BNT-BT)-4KNN ceramic exhibits a dielectric constant exceeding 4000 with excellent dielectric stability from 85 to 370 °C, and demonstrates a high strain of 0.5 % and a Q₃₃of 0.027 m⁴/C²under 100 kV/cm, making it a promising candidate for high-temperature dielectric and electrostrictive applications.