Specific features of the structure and the dielectric properties of sodium–bismuth titanate-based ceramics

The phase formation, specific features, and the dielectric properties of the ceramics of compositions from the region of morphotropic interface in the (Na$_{0.5}$Bi$_{0.5}$)TiO$_{3}$–BaTiO$_{3}$ system modified by Bi(Mg$_{0.5}$Ti$_{0.5}$)O$_{3}$ and also low-melting additions KCl, NaCl–LiF, CuO, and MnO$_2$ that favor the control of the stoichiometry and the properties of the ceramics have been studied. The ceramics are characterized by ferroelectric phase transitions that are observed as jumps at temperatures near 400 K and maxima at $T_m\sim$ 600 K in the temperature dependences of the dielectric permittivity. The phase transitions at $\sim$ 400 K demonstrate the relaxor behavior indicating the existence of polar domains in the nonpolar matrix. An increase in the content of Bi(Mg$_{0.5}$Ti$_{0.5}$)O$_{3}$ favor a decrease in the electrical conductivity and dielectric losses of the samples, and the relative dielectric permittivity at room temperature $\varepsilon_{rt}$ is retained quite high, achieving the highest values $\varepsilon_{rt}$ = 1080–1350 in the ceramics modified with KCl.