Oxygen defect in non-stoichiometric europium orthoniobate, EuxNbO4−1.5(1−x)

The crystal chemistry of non-stoichiometric europium orthoniobate, EuxNbO4−1.5(1−x), prepared using Rb2CO3 flux, was studied. The lattice parameters vary clearly with the rare earth content of the orthoniobate specimens. In the Eu2O3–Nb2O5 system without a flux, the non-stoichiometric compound could not be synthesized as a single phase. With the use of flux, europium-deficient non-stoichiometric solid solution appears to form in which oxygen vacancies are the predominant defects. These non-stoichiometric compounds have the potential to act as new oxide ion conductors.