The structure, phase composition, and migration of oxygen ion in Ce3 NbO7＋δ were reported on the basis of lone-pair substitution concept. X-ray diffraction study revealed that Ce3 NbO7＋δ sample was comprised of Ce3 NbO7＋δ phase and CeNbO4.25 phase. In the dielectric study of Ce3 NbO7＋δ sample, two dielectric loss peaks were observed both in temperature spectra and frequency spectra. Both peaks were shifted towards higher temperature with increase in frequency in temperature spectra and towards higher frequency with increase in temperature in frequency spectra, indicating the relaxation essence of these two peaks. It was suggested that the short distance diffusions of oxygen ions in both Ce3 NbO7＋δ phase and CeNbO4.25 phase gave rise to the two dielectric relaxation peaks.
