Thermodynamic investigation of MF-MgF2 (M = Na, K) system

The molar Gibbs energy of formation of NaMgF3(s) in NaF-MgF2 system and KMgF3(s) and K2MgF4(s) in KF-MgF2 system has been determined using an electromotive force (e.m.f.) technique. For this purpose, fluoride cell has been constructed for each compound using CaF2(s) as the solid electrolyte. From the measured e.m.f. values and required Gibbs energy data available in the literature, a dagger(f) G (o) (m)(T) for NaMgF3(s), KMgF3(s), and K2MgF4(s) have been calculated. To determine the stability domains of NaMgF3(s), KMgF3(s), and K2MgF4(s), the binary phase diagram NaF(s)-MgF2(s) and KF(s)-MgF2(s) and ternary phase diagram Na-Mg-F-2 and K-Mg-F-2 have been calculated and chemical potential diagrams of Na-Mg-F-O and K-Mg-F-O system were calculated.