Effect of SrTiO$_3$, KTaO$_3$, and LiTaO$_3$ modifier on the dielectric properties of Ca$_{0.3}$Ba$_{0.7}$Nb$_2$O$_6$ ceramics

Using the method of solid-phase synthesis, we obtained ceramic samples with a structure like tetragonal tungsten bronzes, pure Ca$_{0.3}$Ba$_{0.7}$Nb$_2$O$_6$ (CBN30) and with modifying additives SrTiO$_3$, KTaO$_3$, or LiTaO$_3$. The dispersion of the permittivity in the frequency range from 1 Hz to 10 MHz, the temperature dependences of the permittivity (in the given frequency range) and the pyroelectric coefficient are studied. It is shown that if the introduction of the LiTaO$_3$ impurity into the composition of CBN30 destabilizes the dielectric characteristics at frequencies above 100 kHz, then the SrTiO$_3$ impurity increases both the permittivity and the pyroelectric coefficient, significantly reducing dielectric losses at low (1–10 Hz) frequencies. At the same time, both of these impurities (SrTiO$_3$ and LiTaO$_3$) lead to sample depolarization during heating above 150$^\circ$C, while the KTaO$_3$ impurity, which slightly increases the permittivity and pyroelectric coefficient, does not affect the stability of the polarized state during heating up to higher temperatures.