The phase equilibrium of the Ag SnS –ZnS pseudobinary system for the growth of Ag ZnSnS (AZTS) crystals was investigated using the equilibration-quenching technique. The growth mechanism of AZTS follows the peritectic reaction liquid phase + ZnS phase ↔ AZTS phase, which occurs at a composition of ~20 mol% ZnS and a temperature of approximately 700 °C. The AZTS polycrystalline sample was obtained from the stoichiometric melt growth. The kesterite structure of the AZTS sample without secondary phases was identified by a combination of X-ray diffraction and Raman spectroscopy measurements. The electron carrier concentration and conductivity, determined by the Hall effect measurement, were (3.0–6.3) × 10 cm and (5.6–9.2) × 10 S/cm, respectively. The slightly Zn-rich and S-poor composition led to n-type conduction in the AZTS because of the dominant Zn antisites on Ag (Zn ) and S vacancy (V ) defects. Therefore, this study can make a significant contribution to the research and application of AZTS materials. 2 3 2 4 Ag S 15 −3 −4