Effects of the sintering temperature on the diffused phase transition and the spin-glassy behavior in Pb_0.95 La_0.05 (Fe _2/3 W_1/3) _0.65 Ti_0.35 O₃ ceramics

In this paper, the effect of the sintering temperature on the low-field dielectric behavior of nonstoichiometric Pb_0.95 La_0.05 (Fe_2/3 W_1/3) _0.65 Ti_0.35 O ₃ relaxor ferroelectrics is investigated. The x-ray patterns and the scanning electron microscope images are used to detect the pyrochlore phase and the perovskite structure. The electric properties of the resistivity, the space charge polarization, the temperature-dependent dielectric constant and dielectric loss are discussed. The diffused phase transition and the ordering state are fitted and discussed by using the empirical law and two ordering models. Furthermore, the glassy behavior is determined by using the Curie-Weiss law and the spin-glass model. According to the experimental data and fitting results, the dielectric picture is changed from the short range order relaxorlike behavior to the long range order normal ferroelectric state as increasing the sintering temperature and the glassy behavior is weakened at the lowest and highest sintering temperature at which the pyrochlore phase PWO ₄ is induced. Therefore, it is suggested that the 1:1 ordered domain is enhanced by increasing the sintering temperature and the glassy behavior is related to not only the ordering degree also the polar defect pairs. For more ordering degree and polar defect pairs, the glassy is weakened and the correlation of neighboring polar microregions is enhanced.