The enthalpies of solution in molten 2PbO · B2O3 of phases synthesized at one atmosphere in the system MgGa2O4-Mg2GeO4 have been measured. A spinel solid solution, which is stable at 1400 °C from the MgGa2O4 end-member to 27 mole percent Mg2GeO4, shows endothermic heats of mixing of up to 10 kJ/mole at the solubility limit. The spinelloid phase, Mg3Ga2GeO8, is energetically less stable than a mixture of terminal spinel solid solutions (0.73 MgGa2O4·0.27 Mg2GeO4(sp)+Mg2GeO4(sp)), by 3.63±3.64 kJ/mole. This indicates that the spinelloid is a high-entropy phase. The volume of the spinel solid solution, MgGa2O4-Mg2GeO4, shows a positive deviation from Vegard's Law. Modeling of the cation distribution in the solid solution indicates that this ΔV is due to a change in the spinel type from inverse towards normal as the Mg2GeO4 content increases.
|Original language||English (US)|
|Number of pages||6|
|Journal||Physics and Chemistry of Minerals|
|State||Published - Apr 1 1989|
ASJC Scopus subject areas
- Materials Science(all)
- Geochemistry and Petrology