Dielectric behavior of lead magnesium niobate relaxors

The dielectric behavior of a solid solution, 10 mol % lead titanate in lead magnesium niobate, is measured at different frequencies from 100 Hz to 100 kHz in the temperature range from -100 to 120 degrees C. A standardizing method is introduced to analyze the curve of the dielectric constant vs temperature. It results a master curve behavior between the dielectric constant and temperature at temperatures higher than the temperature of the dielectric constant maximum. The dielectric relaxation behavior is analyzed with various models. The best way to characterize the degree of the dielectric relaxation for relaxor ferroelectrics is established using the experimental data. It is indicated that the temperature dependence of the static dielectric constant can be well described by an exponential function, while the temperature dependence of the relaxation time is described by a superexponential function. Based on the specialty of the relaxer ferroelectrics, a distribution function for the relaxation times is introduced and a model is introduced to simulate the dielectric behavior of the relaxor ferroelectrics. The model can express well both the temperature and frequency dependence of the dielectric behavior for a relaxor ferroelectrics. All of the parameters in the fitting formula can be experimentally determined. The model shows that in the low-temperature range, there are two simple relationships about the dielectric frequency spectrum: epsilon ''(omega,T)=(-pi/2)partial derivative epsilon'(omega,T)/partial derivative ln omega and epsilon'=B(T)*(ln omega(0)-ln omega). These relationships are verified by the experimental results. A way to obtain the accurate value of epsilon(infinity) in the low-temperature range is described.