An experimental and theoretical investigation on relaxor behavior and local correlations in xBi(Zn0.5Ti0.5)O3-(1-x)BaTiO3 ceramics

Abstract

Relaxor behavior and local correlations in perovskite structured xBi(Zn0.5Ti0.5)O3-(1-x)BaTiO3 (xBZT-(1-x)BT,0.30 ≥x ≥ 0.10) ceramics are investigated by both experimental and theoretical Ab initio molecular dynamics calculations. For 0.30 ≥x ≥ 0.10, xBZT-(1-x)BT ceramics show typical relaxor behavior. For x ≥ 0.20, the J-E loops show “whale” shape and no saturated P-E loops are observed even near the polar nanoregions (PNRs) freezing temperature Tf (135 K–146 K), indicating that long range polar order (ferroelectric domian) does not exist in these samples, and the PNRs locate at nonergodic state with temperature decreasing. The partial pair distribution function (PDF) results show that Bi atoms are very sensitive to the local B site occupancy and have pronounced trend to displace toward neighboring Zn atoms. The Bi-Zn displacement coupling will enhance the local polarization and stabilize the PNRs even at higher temperature. The dipole correlation function (DCF) results show that the Bi dipoles only correlate with their nearest Ti neighbors and the polarization correlation with the second-nearest Ti neighbors is negligible. No existence of long range polar order in xBZT-(1-x)BT (x ≥ 0.20) can be attributed to the Bi displacement influenced highly by the random distribution of Zn atoms and the dominated Bi-Ti dipole correlations only existing within the nearest Bi-Ti neighbors.