Point defects of bismuth in TlInTe$_2$ crystals: electrophysical and dielectric properties of solid solutions

The TlInTe$_2$–Bi phase diagram was studied in the concentration region of 0–10 at.% of Bi by complex methods of physicochemical analysis, and the bismuth solubility in TlInTe$_2$ at room temperature was established to be 5 at.%. The electrophysical and dielectric properties of (TlInTe$_2$)$_{1-x}$Bi$_x$ solid solutions were studied. Using the (TlInTe$_2$)$_{1-x}$Bi$_x$ composition, where $x$ = 0.05, as an example, bismuth impurities were shown to increase the conductivity in direction (001), change the hole conductivity of a TlInTe$_2$ crystal for electron type, and strongly increase the electric anisotropy of a TlInTe$_2$ crystal $\rho\perp/\rho\parallel$ by more than 10$^3$ times. The effect of bismuth impurities on the dielectric properties of TlInTe$_2$ crystals was also observed. Bismuth impurities formed barriers on the migration way of thallium ions and increased the temperature Ti of phase transition into the ion-conducting phase by 69 K in crystallographic direction [001] and 87 K in direction [110].