Dielectric and optical properties, high temperature conduction, and relaxation behavior of donor-element modified NBST material

The relaxor ferroelectrics (Na0.33Bi0.33Sr0.33) (Ti1-xW0.666x)O-3, where 0%<= x <= 7% (NBST+0W, NBST+3W, NBST+5W, and NBST+7W), were prepared using the solid-state reaction method. X-ray diffraction analysis showed that perovskite structures were formed at room temperature. Microstructural characterization, as well as optical and dielectric property measurements, yielded the following results: substituting Ti4+ with the donor element W6+ led to a decrease in the average grain size, dielectric loss, degree of diffusivity, and affected the temperature Tm. In the case of x = 3% of WO3, the electrical conductivity of NBST improved at high temperatures. However, the compound (NBST+7W) exhibited a low optical gap energy and high electrical conductivity at room temperature. The electrical conductivity curves were fitted by Jonscher power law, which showed that the correlated barrier hopping (CBH) model was the most dominant. Comparison of the imaginary part of impedance and electric modulus revealed that the relaxation of charge carriers in the basic compound NBST+0W occurred at both long and short ranges. However, after doping, the relaxation occurred only at a short range.