Étude du système La2S3La2O3Ga2O3Ga2S3: Description structurale des phases quaternaires et approche du diagramme de phase

A description and structural study of four quaternary compounds is furnished: (LaO)4Ga1,33S4 and α-LaGaS2O have sheet structures, formed by (LaO) sheets and gallium sulfide sheets. La3GaS5O has a ribbon structure, formed by (La2O) ribbons inside a LaGaS5 sulfide skeleton. In the three preceding compounds, oxygen is bound only to lanthanum, and gallium is bound only to sulfur. No such bond selectivity occurs in β-LaGaS2O and La3.33Ga6S12O2. An interpretation of the structural characteristics of the Ga(O,S) arrangements is presented in relation to the composition. A partial description of the phase diagram (for O(O + S) < 0.50) is presented. The La2O2SGa2S3 system is quasi-binary. The La2O3Ga2S3 system is a section in the ternary system, involving three-phase equilibria. A description of the eutectic valleys and of the ternary invariants is furnished.