Phase formation in the system Na2O-Ga2O3 has been studied at 800-1350 degrees C via solid-state reaction between gallium oxide and sodium carbonate. Pure Na-P "-gallate was obtained at 1280 degrees C following reaction of the Ga2O3 with the intermediate phases, 3Na(2)O . 5Ga(2)O(3) and Na2O . 3Ga(2)O(3). Na-P "-gallate rapidly hydrates at ambient temperatures and the structural changes involved are reported.