Phase Relations and Lattice Constants in the MgO‐Al 2 O 3 ‐Ga 2 O 3 System at 1550°C

Phase relations and lattice constants in the MgO–Al 2 O 3 –Ga 2 O 3 system at 1550°C have been determined experimentally. In a large part of this system, only a nonstoichiometric spinel is stable. Compositions as extreme as 12.5 mol% MgO–20.5 mol% Ga 2 O 3 –67 mol% Al 2 O 3 for a homogeneous spinel are possible. In the bordering phase diagrams of MgO–Al 2 O 3 and MgO–Ga 2 O 3 , the composition of the spinel is as high as 63 mol% Al 2 O 3 or Ga 2 O 3 , respectively. The contributions of all simple ionic exchange reactions on the lattice constant of the spinel have been deduced from X‐ray diffractometry data.