Calorimetric studies of Ag–Sn–Cu dental amalgam alloy powders and their amalgams

The methods of directed crystallization and thermal analysis were used to construct the section Cu_0.19Fe_0.33S_0.48–Cu_0.31Fe_0.23S_0.46 of the liquid–solid diagram of the Cu–Fe–S system. Pyrrhotite solid solution (Fe, Cu)S_1±δ (Poss) and nonstoichiometric isocubanite Cu_1.1Fe_2.0S_3.0 (Icb*) form from melt (L) successively. Isocubanite forms at 970 °C by peritectic reaction L + Poss → Icb*. At 930 °C, peritectic reaction L + Icb* → Iss proceeds with formation of intermediate solid solution with average composition Cu_1.0Fe_1.2S_2.0 (Iss). On the basis of the results from this paper and earlier published works, we built a fragment of liquidus surface for the Cu–Fe–S system in the crystallization field of nonstoichiometric isocubanite and stoichiometric isocubanite CuFe₂S₃ (Icb).