Dielectric relaxation in PLT (Pb1-xLaxTiO3) ceramics in the microwave region (0.05-2.0 Ghz)

Dielectric dispersion was determined in PLT (Pb1-xLaxTiO3) ceramics (0.05 less than or equal to x less than or equal to 0.30) prepared by conventional ceramic method. The measurements were made in the frequency range of 0.05 MHz -2.0 GHz as a function of the temperature between -50 degrees C and 300 degrees C. Experimental results showed a dielectric relaxation, in the frequency range between 0.5 GHz and 1.5 GHz, for samples that display normal phase transition (x < 0.25) as well as samples with diffuse phase transition (x greater than or equal to 0.25). The characteristic frequency (f(0)) of the relaxation process was minimum at the temperature of maximal dielectric constant (T-max) for "normal" ferroelectric compositions. For compositions with diffuse phase transition (relaxor) the minimum of f(0) occurred at temperature lower than T-max.