TlGa1 − xErxS2 (x = 0, 0.001, 0.005, 0.01) solid solutions, based on the layered compound TlGaS2, have been prepared by direct elemental synthesis. The effect of Er concentration on the dielectric and

We have constructed the T-x phase diagram of the TlGaS₂-TlFeS₂ system (simple eutectic system, eutectic at 80 mol % TlFeS₂ with a melting point of 953 K). The system contains limited series of monoclinic solid solutions based on the ternary end-members. At an annealing temperature of 933 K, the TlGaS₂-based solid solution extends to 5 mol % TlFeS₂ and the TlFeS₂-based solid solution extends to ≅10 mol % TlGaS₂. We have examined the effect of partial iron substitution for gallium on the optical properties of melt-grown single crystals of the TlGaS₂-based solid solutions and determined their band gap as a function of temperature and Fe concentration.

The band structure, density of states, and electronic properties of a 32-atomic supercell of a semiconductor compound TlGaS₂ containing neodymium are calculated. On the grown new single crystals of TlGaS₂ : Nd³⁺ (0.3 mol% Nd₂S₃), experimental results on the physical properties have been obtained. The temperature (93-538 K) and frequency (5·10⁴-3.5·10⁷ Hz) dependences of the dc and ac conductivity and the frequency dispersion of the dielectric coefficients of TlGaS₂ : Nd³⁺ single crystals have been studied. It was found that in TlGaS₂ : Nd³⁺, in the entire studied frequency range, there are losses due to electrical conductivity, and the charge transfer has a hopping character. The parameters of localized states are estimated, such as the density of localized states near the Fermi level and their spread, the average hopping time and distance, and the concentration of deep traps responsible for the dc and ac conductivity in TlGaS₂ : Nd³⁺. Keywords: DFT calculation, TlGaS₂ supercell, neodymium doping, energy structure, density of states, dielectric properties, charge transfer, TlGaS₂ : Nd³⁺ single crystal, direct and alternating current.

The real and imaginary parts of the complex dielectric permittivity, the dielectric loss tangent, and ac conductivity of crystals of TlInSe₂-TlGaTe₂ solid solutions have been measured as functions of frequency in the range 50 kHz to 35 MHz, and the ΔG _T ⁰ and heat capacity of the (TlInSe₂)_{1 − x} (TlGaTe₂) _x solid solutions have been determined as functions of temperature. The results demonstrate that, over the entire composition range, the measured physical properties of the solid solutions correlate with their composition.

It is revealed that TlS single crystals exhibit a variable range hopping conduction along a normal to their natural layers at temperatures T ≤ 230 K in a dc electric field and a nonactivated hopping conduction at low temperatures in strong electric fields. Estimates are made for the density of states near the Fermi level (N _F = 2.8 × 10²⁰ eV⁻¹ cm⁻³ and their energy spread (ΔW = 0.02 eV), the localization radius (a = 33 Å), the average jump distance in the region of activated (R _av(T) = 40 Å) and nonactivated (R _av(F) = 78 Å) hopping conduction, and also the drop in the charge carrier potential energy along the jump distance in an electric field F: eFR = 0.006 and 0.009 eV at F = 7.50 × 10³ and 1.25 × 10⁴ V/cm, respectively.

CdGa2S4 single crystals have been grown from a presynthesized source material by closed-tube iodine vapor transport, and their X-ray dosimetric properties have been studied. Their X-ray sensitivity co