PHASE-RELATIONS AND LATTICE-CONSTANTS IN THE MGO-AL2O3-GA2O3 SYSTEM AT 1550-DEGREES-C

Phase relations and lattice constants in the MgO-Al2O3-Ga2O3 system at 1550 degrees C have been determined experimentally. In a large part o f this system, only a nonstoichiometric spinel is stable. Compositions as extreme as 12.5 mol% MgO-20.5 mol% Ga2O3-67 mol% Al2O3 for a homog eneous spinel are possible. In the bordering phase diagrams of MgO-Al2 O3 and MgO-Ga2O3, the composition of the spinel is as high as 63 mol% Al2O3 or Ga2O3, respectively. The contributions of all simple ionic ex change reactions on the lattice constant of the spinel have been deduc ed from X-ray diffractometry data.