High thermally stable dielectric permittivity, polarization enhancement and electrostrictive properties in Zr-substituted bismuth sodium titanate lead-free ferroelectric ceramics

Zr-substituted (Bi0.5Na0.5)(Ti1-xZrx)O-3 (BNTZ) with x = 0.02-0.4 ceramics were prepared using solid-state reaction technique and their structural, dielectric and ferroelectric properties were investigated systematically. X-ray diffraction results suggest that Zr4+ ion can enter the (Bi0.5Na0.5)TiO3 (BNT) crystal lattices at a limited value and a secondary phase appears in BNTZ ceramics when the x exceeds 0.1. Temperature-dependent di-electric permittivities of BNTZ ceramics show only one dielectric peak from room temperature to 500 degrees C for each composition, and this dielectric peak becomes broad gradually as x increases from 0.02 to 0.4. The permittivity of x = 0.4 varies less than +/- 10% between room temperature and 300 degrees C, indicating a superior thermal stability of the permittivity. Polarization enhancement is revealed by the polarization-electric field hysteresis loops and highest ferroelectric properties are obtained in x = 0.04. The electric-field-induced strains of x = 0.04 show a monotonous increase as temperature increases from 30 degrees C to 150 degrees C. At 80 kV/cm, a high strain level of 0.268% is achieved. Our results suggest that the introduction of Zr4+ ion could effectively tailor the dielectric and ferroelectric properties of BNT ceramics and x = 0.4 composition could find potential application in high temperature capacitor devices.