The Room Pressure Spinelloid Phases of the NiGa2O4 - Ni2SiO4 System

Abstract

<p> The ternary oxide system NiO - Ga2O3 - SiO2 has been studied in the temperature range 1400-1550°C at room pressure. Three phases, corresponding to the spinelloid phases I, II, and V, have been identified on the Ni2GaO4 (spinel) - Ni2SiO4 (olivine) join. These room-pressure phases are isostructural with the high-pressure spinelloid phases of the nickel aluminosilicate system. Single crystals of all three phases have been grown from a silica-rich melt and their crystal structures have been determined by X-ray diffraction. The structure refinements have revealed a strong ordering of the Ga and Si atoms on the tetrahedral sites of all three phases, as well as a clear correlation between spinelloid structure-type and composition. This correlation accounts for the increase in Ni2SiO4 content across the series spinel - phase V - phase I - phase II.</p>