Dielectric response of 0.85 Ba(Ti0.96Zr0.04)O_3-0.15 Bi(Mg_(0.5)Ti_(0.5))O_3 relaxor ferroelectrics under electric field: evolution of PNRs

摘要

0.85 Ba(Ti_(0.96)Zr_(0.04))O_3-0.15 Bi(Mg_(0.5)Ti_(0.5))O_3 relaxor ferroelectric ceramic samples were synthesized through traditional solid state reaction method. The asymmetric single peak of (200) at 45° was revealed by XRD measurement, combined with diffuse phase transition peaks in dielectric-temperature spectrum and a slim but discernible hysteresis loop, which proved the existence of the polar nano-regions (PNRs) in paraelectric matrix of the sample. The investigation of dielectric response of the ceramic samples under electric field (changing field magnitude and field history) was employed to analysize the evolution of PNRs. Electric field dependence of dielectric constant was obtained both by small signal bias electric field measurement and differential calculation from P-E curves, they all reached the maximum value firstly at the critical electric field and then decreased with the continuous increasing of electric field, instead of decreasing directly. However, the value of dielectric constant and critical field of bias electric field measurement was hys-teretic electrically to those of differential calculation from P-E curves. Both the glassy model and macro-micro theory model were employed to explain and explore the evolution of PNRs, though from different perspective.