TEMPERATURE-DEPENDENCE OF THE DIELECTRIC-CONSTANT OF RELAXOR FERROELECTRICS

The temperature dependence of the dielectric constant under different frequencies is measured and analyzed for two different relaxer ferroel ectrics, the solid solution ceramics of lead magnesium niobate and lea d zinc niobate, respectively. Compared with the experimental results, the disadvantage of simulated results from different methods about the temperature dependence of the dielectric constant for relaxors is giv en. Based on this and the general behavior of the temperature dependen ce of the dielectric constant at both high and low temperatures, it is assumed that there are two kinds of polarization processes in the rel axer ferroelectrics. One of the polarization processes is associated w ith the thermally activated flips of the polar regions in the material s. Thus, a set of formulas is proposed to fit the temperature dependen ce of the dielectric constant at different frequencies. The formulas a re strictly certified with the measured data of both materials. The fo rmulas can fit the measured relation with high precision. The fitted r esults confirm and/or show the following: (1) The dielectric behavior at high temperatures is mainly contributed from a relaxation polarizat ion process, which is associated with the thermally activated flips of polar regions in relaxer ferroelectrics. (2) The dielectric behavior at low temperatures is mainly contributed from the other polarization process. The frequency dependence of the dielectric constant shows tha t this process is something like a resonance polarization in the mater ials. (3) The dielectric behavior at temperatures around the temperatu res of the dielectric constant maximum is determined with both polariz ation processes. The micro-origin of the resonance polarization is dis cussed with the breathing of frozen polar region in the materials. Bas ed on the breathing model, all of the characteristics of the resonance polarization are explained. The amplitude dependence of the dielectri c constant for relaxer ferroelectrics is also explained with the breat hing model.