Dielectric nonlinearity of relaxor ferroelectric ceramics at low ac drives

摘要

Dielectric nonlinear response of(PbMg$_{1/3}$Nb$_{2/3}$O$_3$)$_{0.9}$(PbTiO$_3$)$_{0.1}$ (0.9PMN-0.1PT) relaxorceramics was investigated under different ac drive voltages. It was observedthat: (i) the dielectric permittivity is independent on ac field amplitude athigh temperatures; (ii) with increasing ac drive, the permittivity maximumincreases, and the temperature of the maximum shifts to lower temperature;(iii) the nonlinear effect is weakened when the measurement frequencyincreases. The influences of increasing ac drive were found to be similar tothat of decreasing frequency. It is believed that the dielectric nonlinearitiesof relaxors at low drives can be explained by the phase transition theory ofergodic space shrinking in succession. A Monte Carlo simulation was performedon the flips of micro polarizations at low ac drives to verify the theory.