The crystal chemistry of non-stoichiometric europium orthoniobate, EuxNbO4-1.5(1-x), prepared by using a Rb2CO3 flux, was studied. The lattice parameters clearly varied with the rare-earth content of the specimens. The non-stoichiometric compound could not be synthesized as a single phase, in the Eu2O3-Nb2O5 system, without a flux. Upon using a flux, Eu-deficient non-stoichiometric solid solutions formed in which O vacancies appeared to be the predominant defects. These non-stoichiometric compounds had potential as new oxide-ion conductors.

Oxygen Defect in Non-Stoichiometric Europium Orthoniobate. K.Toda, M.Honda, Y.Ishimoto, Z.G.Ye, M.Sato: Solid State Ionics, 2000, 136-137, 25-30