Polymorphic transformation in nanocrystalline silver sulfide

The $\alpha$-Ag$_{2}$S acanthite–$\beta$-Ag$_{2}$S argentite phase transformation in nanocrystalline silver sulfide has been studied in situ for the first time using high-temperature X-ray diffraction and scanning electron microscopy. The formation of argentite has been proved by differential thermal analysis. The acanthite–argentite transformation occurs at a temperature of $\sim$449–450 K, and its enthalpy is $\sim$3.7–3.9 kJ mol$^{-1}$. The thermal expansion coefficients of acanthite and argentite have been estimated.