Structure and dielectric properties of solid solutions Bi7Ti4+xWxNb1-2x-0.1V0.1O21 (x = 0.1 - 0.4)

The structural and electrophysical characteristics of a number of solid solutions of layered oxides of the perovskite-type Bi7Ti4+xWxNb1-2x-0.1V0.1O21 (x = 0.1 - 0.4) are studied. According to X-ray powder diffraction data, all the compounds studied are single-phase and have the structure of Aurivillius phases (m = 2.5) with a rhombic crystal lattice (space group I2 cm, Z = 2). Changes in tetragonal and rhombic distortions of perovskite-like layers in compounds were considered depending on their chemical composition. The temperature dependences of the relative permittivity epsilon (T) were measured. It was shown that the Curie temperature T-C of the perovskite-type oxides Bi7Ti4+xWxNb1-2x-0.1V0.1O21 (x = 0.1 d- 0.4) linearly decreases with increasing parameter x. The activation energies of charge carriers were obtained in different temperature ranges. It was found that there are three temperature regions with very different activation energies due to the different nature of the charge carriers in the studied compounds. The effect of substitution of Nb5+ ions by V5+ ions is investigated. It was found that for a number of compounds, the substitution of niobium ions by vanadium ions led to an increase in the dielectric constant and a decrease in the dielectric loss tangent.