| In this paper, six Ce:LiNbO3 crystals in which the doping concentration is 0.1mol% with various Li/Nb mole ratios (0.750, 0.850, 0.946, 1.100, 1.250, 1.38) were grown by Czochralski method. Some of the samples were oxidized and reduced. The influence of varied Li/Nb on the intrinsic defect, location of doped ion in the crystals were investigated by measuring the X-ray power diffraction, Differential thermal analysis, Infrared spectra and Ultraviolet-visible absorption spectra. The influence of difference treatment on the defect structure were also analysed.X-ray powders diffraction of the crystals were carried out. The results showed that all the Ce:LiNbO3 crystals hold the same lattice structures as the pure congruent LiNbO3. It demonstrated that the Ce ion enter lattice by the replacement of Li or Nb ions. Compared with the pure congruent LiNbO3 crystal's, doped LiNbO3 crystals have longer c axis and bigger crystal volume. With the increasing of Li/Nb ratios, the length of a axis become longer, but the length of c axis and crystal volume don't change regularly.Using differential thermal analysis, infrared spectra and ultraviolet-visible absorption spectra, the location model of Ce ion in the crystals was confirmed, that is before the crystal achieves stoichiometric Ce takes Li sites, and then Ce enter NbNb sites. Because of the cooperation of Li/Nb ratios and Ce ion, the crystal achieves to stoichiometic. When the melt with the Li/Nb ratio of 1.250, its stoichiometry crystal.The photo-refractive properties including diffraction efficiency, writing time, erase time, the photo-refractive sensitivity and the dynamic range were measured. We found that the photo-refractive properties of the Ce:LiNbO3 crystals are affected by the Li/Nb ratio and the treating state of crystals. The results showed that the diffraction efficiency increase, writing time decrease, and the photorefractive sensitivity and the dynamic range are enhanced with the increasing of Li/Nb ratio, but they will go to the opposite direction when the Li/Nb ratio reaches the opportune one. The diffraction efficiency increase, photorefractive sensitivity and the dynamic range are enhanced, but the writing... |
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