A method of forming metal oxide powders includes the steps of solid state mixing of at least one metal nitrate salt, such as Fe(NO.sub.3).sub.3 or a combination of metal nitrate salts such as Zn(NO.sub.3).sub.3,6H.sub.2O and Ga(NO.sub.3).sub.3, xH.sub.2O, and at least one reducing organic acid, such as tartaric or citric acid. The mixture is heated to form a metal oxide powder, such as alpha-iron oxide (.alpha.-Fe.sub.2O.sub.3) or a mixed metal powder such as zinc gallate phosphor (ZnGa.sub.2O.sub.4). A metal oxide precursor intermediate can be formed and then heated to form the metal oxide powder.