Exsolution of β‐Ga ₂ O ₃ Crystalline Solutions in the System MgAl ₂ O ₃ ‐Ga ₂ O ₃

Abstract

The subsolidus phase equilibrium diagram for the pseudobinary join MgAl 2 O 4 ‐Ga 2 O 3 was determined. The shape of the exsolution boundary was obtained by heat‐treating samples pre‐ equilibrated at 1600°C. Crystalline solubility of Ga 2 O 3 in MgAl 2 O 4 decreased from 73 mole % at 1600°C to 55 mole % at 1200°C. The crystalline solution was formed by the replacement of Mg 2+ ions by Ga 3+ ions to produce a cation defect spinel. The phase precipitated was the mono‐clinic δ‐Ga 2 O 3 (=δ‐Al 2 O 3 structure). Changes in the ratios of relative X‐ray diffraction intensities indicated that the crystalline solutions also disorder with temperature.