Thermal expansion and the heat capacity of nanocrystalline and coarse-crystalline silver sulfide Ag2S

The thermal expansion and the heat capacity of coarse-crystalline and nanocrystalline silver sulfide Ag₂S were studied by dilatometry and differential scanning calorimentry for the first time in the temperature range 290–970 K. It is found that the thermal expansion coefficient and the heat capacity of nanocrystalline silver sulfide in this temperature range are higher than those in the case of the coarse-crystalline sulfide. It is revealed that the transformation of α-Ag₂S acanthite to β-Ag₂S argentite and β-Ag₂S argentite to γ-Ag₂S phase are the first-order phase transitions; the temperatures and the enthalpies of these transformations have been determined.