A new type of chalcogenide crystals Tl 4 SnS 3 , Tl 4 SnSe 3 , Tl 4 SnTe 3 easily processing by external IR laser light is fabricated. For the titled crystals linear electrooptical effect was induced by external IR polarized light formed by two coherent beams of Er:glass nanosecond laser at fundamental wavelength 1540 nm. The detection of the electrooptical coefficient was performed by continuouswave 1 W CO 2 laser at probing wavelength 10.6 lm. The origin of the effect is caused by an occurrence of the thin (up to 50 nm) photoexcited nanosheets which forms near the surface space charge density non-centrosymmetry. The relaxation of the electrooptics after switching off of the photoinduced Er:glass laser beam is explored for different types of samples at different power densities. The crystals may be used for IR optical triggering.

Cu7PS6 crystals were grown using direct crystallisation from the melt (Bridgman–Stockbarger technique). The crystal structure of Cu7PS6 was determined by X-ray powder diffraction. Cu7PS6 crystallise in the cubic structure, space group P213 (No. 198), the lattice parameter a = 9.6706(1) Å, formula units per cell Z = 4. Electrical properties of Cu7PS6 crystals were studied in the frequency range 10–1010 Hz and in the temperature interval 296–351 K. The performed analysis shows that the Cu7PS6 crystals are mixed electron-ionic conductors with some growth defects.

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