Effect of the la concentration on the dielectric and optical properties of the transparent ferroelectric ceramics 75PbMg1/3Nb2/3O3-25PbTiO3

The dielectric, optical, and electro-optical properties of transparent ferroelectric ceramics 75PbMg1/3Nb2/3O3-25PbTiO3 (75PMN-25PT) with different La concentrations (2, 3, and 4 at %) have been studied. It has been shown that all the samples under study undergo a diffuse phase transition, and the degree of diffuseness increases with an increase in the La concentration. The temperature dependences of the optical transmission in different regimes of applying an electric field and the quadratic electro-optical effect have been investigated. It has been found that, at room temperature, the maximum electro-optical effect is observed in the ceramics with a La concentration of 3 at %. This is explained by the fact that the measurement temperature is close to the Vogel-Fulcher temperature at which the minimum electric field is required to induce ferroelectric states from the relaxor phase.