Reactions of the oxides of niobium with liquid potassium

Abstract

The reactions of the oxides Nb₂O₅, NbO₂, and NbO with liquid potassium have been studied at temperatures of 400°(Nb₂O₅) and 600°(all three). Reaction products are black, hygroscopic powders, which have been examined by X-ray powder crystallography. In each case the equilibrium products prove to be niobium metal and a low-temperature form of potassium orthoniobate, K₃NbO₄. The latter has also been prepared in a pure state, and its X-ray powder diffraction pattern defined. The co-existence of niobium in the Nb⁰ and Nb^V states in the product is discussed in the light of possible reaction mechanisms, and the stability of the MO₄^n– species in the liquid metal. Potassium monoxide also reacts with niobium metal at 260° to give K₃NbO₄.