Journal of Alloys and Compounds 399 (2005) 32–37 Phase diagram of the Ag 2 S–HgS–SnS 2 system and single crystal preparation, crystal structure and properties of Ag 2 HgSnS 4 O.V. Parasyuk a,∗ , S.I. Chykhrij b , V.V. Bozhko c , L.V. Piskach a , M.S. Bogdanyuk c , I.D. Olekseyuk a , L.V. Bulatetska c , V.I. Pekhnyo d a Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk, Ukraine b Department of Analytical Chemistry, Ivan Franko National University of L’viv, Kyryla and Mefodiya St. 6, 79005 L’viv, Ukraine c Department of Solid State Physics, Volyn State University, Voli Ave 13, 43009 Lutsk, Ukraine d V.I. Vernadskii Institute of General and Inorganic Chemistry of the Ukrainian National Academy of Sciences, Palladina Ave 32–34, 03680 Kyiv, Ukraine Received 22 February 2005; accepted 9 March 2005 Available online 1 April 2005 Abstract The phase equilibria in the quasi-ternary system Ag 2 S–HgS–SnS 2 at 298 K were investigated using X-ray diffraction. The existence of the Ag 2 HgSnS 4 compound that is the only one at this temperature was confirmed. The vertical section Ag 8 SnS 6 –HgS was constructed. It is of the eutectic type (eutectic point coordinates are 89 mol% HgS and 881 K), with the formation of a HT–Ag 8 SnS 6 solid solution range extending to ∼57 mol% HgS at 881 K. The Ag 2 HgSnS 4 crystal structure was refined using X-ray powder diffraction. Ag 2 HgSnS 4 crystallizes in the orthorhombic space group Pmn2 1 (ST Cu 2 CdGeS 4 ) with unit cell parameters a = 0.82074(4) nm, b = 0.70330(3) nm and c = 0.67180(3) nm. The atomic parameters were refined in the isotropic approximation to R = 0.0795. Ag 2 HgSnS 4 single crystals (Ø = 10–12 mm; l = 30 mm) were grown using the Bridgman–Stockbarger technique. The single crystals exhibit n-type semiconductor conductivity. The photoconductivity spectra at liquid nitrogen and room temperatures were investigated, and their non-elementary nature was shown. © 2005 Elsevier B.V. All rights reserved. Keywords: Semiconductors; X-ray diffraction; Phase diagrams; Thermal analysis 1. Introduction We have earlier investigated the quasi-ternary sys- tems Ag 2 S–HgS–GeS 2 [1], Ag 2 Se–HgSe–SiSe 2 [2], Ag 2 Se–HgSe–GeSe 2 [3] and Ag 2 Se–HgSe–SnSe 2 [4].A number of new quaternary compounds were found in these systems. Here, we report on the results of the investigation of the phase equilibria in the Ag 2 S–HgS–SnS 2 system as well as on single crystal growth and on the results of crystal structure refinement and certain physical properties of Ag 2 HgSnS 4 . The quaternary compound Ag 2 HgSnS 4 was first synthesized by Haeuseler et al. [5]. The synthesis was performed from the elements and preliminarily synthesized ∗ Corresponding author. E-mail address: oleg@lab.univer.lutsk.ua (O.V. Parasyuk). HgS at 970 K. These authors established that the compound crystallizes in wurtzite–stannine structure (Table 1). Its FIR-absorption spectra were studied [6]. Ag 2 HgSnS 4 melts congruently at 933 K [7] and forms eutectics with Ag 2 SnS 3 and HgS that are the components of the corresponding quasi-binary sections. The phase diagrams of the quasi-binary systems that limit the quasi-ternary system were investigated in [1,8–10]. The Ag 2 S–HgS [1] and HgS–SnS 2 [8,9] systems are of eu- tectic type. No ternary compounds were found there. In the Ag 2 S–SnS 2 system, Gorochov [10] has discovered an Ag 8 SnS 6 compound that melts congruently at 1112 K, is di- morphous (T PT = 445 K), and forms eutectics with the com- ponents of the system. The diagram constructed by Kokhan [11] contains three compounds. Ag 8 SnS 6 and Ag 2 SnS 3 melt congruently at 1121 and 936K, respectively. The Ag 8 SnS 6 0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.03.008