Thermal properties and optimization of process parameters for the growth of silver thiogallate crystal by differential scanning calorimetry

In present work, thermal properties of silver thiogallate (AgGaS2) crystal were investigated by means of differential scanning calorimetry (DSC) measurements performed at different heating and cooling rates. The DSC results confirmed that the melting point was 1249 K with a slight change around 5 K and that the nucleation temperature varied from 1183 K to 1218 K. The supercooling temperature was evaluated in the range 37.69 K to 62.46 K which was considered to be harmful for the single nucleus formation at the beginning of crystal growth. The activation energy E and the pre-exponential factor A were also calculated using different isoconversional methods, namely Kissinger-Akahira-Sunose (KAS) method and Flynn-Wall-Ozawa (FWO) method, and the results showed good agreement with each other. According to the results of DSC, a larger temperature gradient up to 30 K/cm was utilized to suppress the formation and growth of multi nuclei and a rapid cooling rate 25 K/min was applied to minimize the second-phase precipitates during the process of crystal growth. Finally, an integral and transparent AgGaS2 single crystal with diameter of 22 mm and the length of 55 mm was obtained.