Levkovets S. Phase equilibria, crystal structure and the properties of intermediate compounds in the 2TlI + Hg(Pb)Br2 ↔ Hg(Pb)I2 + 2TlBr and related systems

The thesis contains the results of the investigation of the phase equilibria in the quasi-ternary reciprocal systems 2TlI + Hg(Pb)Br2 ↔ Hg(Pb)I2 + 2TlBr. Two isothermal cross sections and liquidus surface projections of the quasi-ternary reciprocal systems 2TlI + Hg(Pb)Br2 ↔ Hg(Pb)I2 + 2TlBr at 298 K were investigated from XRD, DTA and microstructure analysis results. Six compounds were found for the first time: 1 ternary (Tl2PbBr4), 4 quasi-ternary (Tl4HgBr4I2, Tl5Hg2Br5I4, Tl2Hg2Br3I3, TlPb2BrI4) and 1 related (Tl5Hg2Cl5I4); the existence of another 9 known ternary compounds was confirmed (15 compounds in total). The crystal structure of Tl5Hg2Br5I4, Tl5Hg2Cl5I4 (SG I4/mcm, new structure type), TlPb2BrI4 (SG I4/mcm, structure type NH4Pb2Br5) was studied. The single crystals of Tl10Hg3Cl16, Tl4HgBr6, Tl4HgI6 (100g), TlHgCl3, TlHgBr3, Tl3PbI5, TlPbI3, Pb5Br6I4, Tl2PbBr4, TlPb2Br5-xIx (x = 2.0÷4.5), Tl3PbBr2.5I2.5 were grown by Bridgman-Stockbarger method. Electronic structure, оptical and non-linear optical properties of grown single crystals (second harmonic generation, two-photon absorption, piezoelectric effect) were investigated.