Polymorphism of Ga2O3and the System Ga2O3−H2O

Abstract

An investigation of freshly precipitated gallia gel by X-ray and electron diffraction techniques has led to the conclusion that the gel is at first a gallia-water complex, not α-Ga2O3as supposed by Weiser and Milligan. On aging, the gel transforms to the GaO2H structure, but the gel may dehydrate, before the GaO2H lattice can develop, to form α-Ga2O3or γ-Ga2O3. Besides α-, β- and γ-Ga2O3, two new polymorphs called herein δ-Ga2O3and ϵ-Ga2O3have been found. X-Ray data and the conditions under which these structures appear are given. The stable form of gallia from room temperature to its melting point is β-Ga2O3. Data for the system Ga2O3−H2O were obtained over the pressure range 50 to 25,000 p.s.i., at temperatures up to 800°. The temperature of transformation of GaO2H to β-Ga2O3plus water as determined by Laubengayer and Engle (300°) was confirmed and it was found that this temperature is not affected appreciably by pressure in the range used. © 1952, American Chemical Society. All rights reserved.