SYNTHESIS AND STRUCTURE HOMOGEINITY OF PYRARGYRITE

Abstract

The work is devoted to study peculiarities of obtaining single crystal of the Ag3SbS3 compound (the analogue of natural pyrargyrite. The material is prospective for non-linear optics, sensor technology and optoelectronics. The single crystal of the Ag3SbS3 compound was obtained with Bridgman-Stockbarger method in vertical two-zone resistance furnace with programmable temperature control. The temperature of of the melt zone was 783 K, annealing zone – 663 К. Crystal growth was rapid 0,10-0,24 mm/h; the temperature gradient in the growth zone was 4-6 K/mm. For the synthesis, a pre-cleaned quartz ampoule with a composition that was vacuumed to a residual pressure of 10-2 Pa has been used. For the obtaining the single crystal of Ag3SbS3 individual components (silver, antimonium and sulfur) with semiconductor purity were used. In order to analyze phase composition and calculate the crystal structure, the diffractgram of grown single crystal was obtained with using Diffractometer DRON- 4-13 (CuKα-radiation; the range 10≤2Θ≤80°; step 0,02°; time 15°s). The crustal structure has been calculated by Rietveld method. A program package WinCSD was used for calculations. The crystal structure of single crystal of the Ag3SbS3 belongs to trigonal system (Structure Type Ag3AsS3 (Prustite); SG R3c; Pearson symbol hR14,161). The calculated lattice parameters are a = 1.10402(9) nm, b = 0.8713(1) nm, V = 0.9197(3) nm3. In the structure of Ag3SbS3 Ag and S atoms are located in the site 18b and Sb atoms are in the site 6а. The study of the quantitative and qualitative composition of samples of the grown single crystal of the studied compound was carried out by the methods of energy dispersive spectroscopy (EDS) and energy dispersive X-ray spectroscopy (EDX) (scanning electron microscope Tescan Vega 3 LMU (SEM)). SEM images and results of energy dispersive X-ray analysis were obtained at a voltage of 20–25 kV under conditions of high vacuum (9.0·10–2 Pa).