Thermal expansion and the heat capacity of nanocrystalline and coarse-crystalline silver sulfide Ag$_{2}$S

The thermal expansion and the heat capacity of coarse-crystalline and nanocrystalline silver sulfide Ag$_{2}$S 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 $\alpha$-Ag$_{2}$S acanthite to $\beta$-Ag$_{2}$S argentite and $\beta$-Ag$_{2}$S argentite to $\gamma$-Ag$_{2}$S phase are the first-order phase transitions; the temperatures and the enthalpies of these transformations have been determined.