A crystal growth practice was developed for producing monocrystals of the gallium analog of β′-Al2O3. The method involves evaporation of Na2O from a molten Na2O-Ga2O3 charge held in a boat that is located in a furnace with a steep temperature gradient so that the product grows from one end. Monocrystals up to about 1 cm in size have been grown. Their composition is Na2O.5.7Ga2O3, which corresponds to 96.5% occupancy of the available Na sites. The space group is R3m and the lattice parameters are a = 5.84Å and c = 34.53Å. © 1977, The Electrochemical Society, Inc. All rights reserved.