The effect of hydrostatic pressure on the electrical conductivity of a TlInSe2 single crystal along the tetragonal axis [001] is studied in the range from 0 to 14 × 106 kPa. It is revealed that in this case the dependence of electrical conductivity on pressure follows the law: σ(P) =σ(0) e−GP/2kT which holds true for cases of linear narrowing of the band gap with pressure. It is found that the pressure coefficient of the band gap G = ∂Eg(P)/∂P responsible for the change in the electrical conductivity with pressure amounts to G = (∂ In σ(P)/∂P) 2kT = −1.75 × 10−10eV/Pa which coincides in the order of magnitude with the coefficient G[001] = −(3 to 4) × 10−10 eV/Pa characterizing the narrowing (widening) of the indirect energy gap for a uniaxial compression (expansion) of the given crystals along [001].
According to the data of differential thermal, X-ray phase analyzes, as well as measurements of conductivity and pycnometric density, phase equilibriums were studied and phasing diagrams of TlInS2-CuInS2 and TlGaSe2-CuGaSe2 systems were created in the entire concentration range. The studied systems are quasi-binary with limited mutual solubility of the components in the solid state. The interaction in the TlGaSe2-CuGaSe2 system occurs with the formation of one eutectic and one peritectic points, in the TlInS2 system-CuInS2 with the formation of one eutectic and two peritectic points. Eutectic at 1048 K corresponds to 18 mol. % CuGaSe2 and at 945 K 17-mol. % CuInS2. Solid solutions based on CuGaSe2, CuInS2, like the initial compounds themselves, undergo phase transformations. It is found that in these systems limited solid solutions are formed, which make up 1.5 mol. % at indoor temperature on TlGaSe2 and 0.5 mol. % on CuGaSe2 in the TlGaSe2-CuGaSe2 system, as well as 1.5 mol. % on TlInS2 and 0.5 mol. % on CuInS2 in the TlInS2-CuInS2 system. The nature of the interactions of the components makes it possible to assign the presented phasing diagrams to type VI according to Rooseboom.
We have studied the effect of uniaxial compression (stretching) deformation on electrical conductivity along the crystallographic axis [00l] of monocrystals TlInSe2 and derivant solid solutions. It has been found that substitution of Tl atoms with Ag atoms in crystals of solid solutions based on TlInSe2 leads to a shift of the energy of indirect transitions to the long-wave zone. The obtained results have been compared to both theoretical calculations of the zone structure of TlInSe2 crystals and the multi-valley model.
Phase equilibrium was studied on the basis of the data of differential thermal, X-ray phase analyzes, as well as measurements of conductivity and density. Phasing diagrams of TlInSe2-CuInSe2 and TlInSe2-AgInSe2 systems were constructed over the entire concentration range. The studied systems were quasi-binary with limited mutual solubility of the components in the solid state. State diagrams were eutectic in nature. The areas of mutual solubility at eutectic temperatures were approximately 3 mol. % on each side in the TlInSe2 system-CuInSe2 and 15 mol. % on the basis of TlInSe2 and 5 mol. % based on AgInSe2 in the TlInSe2-AgInSe2 system. The solid solutions based on CuInSe2 and AgInSe2, as well as the initial compounds themselves, undergo phase transformations from the chalcopyrite structure to the sphalerite structure. It was found that in these systems limited solid solutions were formed, which were 2.5 mol. % at indoor temperature from TlInSe2 and 1.5 mol. % on CuInSe2 in the TlInSe2-CuInSe2 system and 3 mol. % on TlInSe2, 2 mol. % on AgInSe2 in the TlInSe2-AgInSe system.
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