Growth And Structure Analysis Of Co-Doped Lithium Niobate With Mg, Mn And Fe

LiNbO3 crystal has the photorefractive effect, and can be used as the material of optical holographic storage. In this paper it is described the whole process in which the Mg:Mn:Fe:LiNbO3 crystal series are grown in approach of Czochralski, without macroscopic defect while exhibiting good optical homogeneity. Appropriate parameters (temperature gradient, pulling speed and rotating speed) are chosen during the crystal growth process to maintain the flat solid-liquid interface and decrease the disuniformity of compositions to the extreme extent, which is resulted from the solution segregation. The result of X-ray fluorescence inspection shows that with the increase of the doped Mg amount efficient segregation coefficient of Mg element decreases, that of Mn maintains 1 or so and that of Fe increases slightly. The result of differential thermal analysis measurement shows that Curie temperature of crystals increases with the increase of doped Mg amount in the raw material. As the polarizing temperature is more than Curie temperature by 5~10℃, a better polariation is achieved. The polarizing temperature is chosen more than Curie temperature and polarized crystals are proved in single domain.When the coped Mg amount is 6mol.%, O-H infrared vibration absorption peak of Mg: Mn:Fe:LiNbO3 crystal shifts from 3482 cm-1 for lower Mg doped amount to 3535 cm-1for this increased doped amount compared with that of other crystals doped with lower Mg concentration, which indicates that this doped Mg concentration of 6mol.% is the threshold. With the increase of Mg doping amount, the absorption edge in ultraviolet-visible absorption spectra of Mg:Mn:Fe:LiNbO3 crystal relatively shifts to the violet and then inversely to the red when Mg doping concentration is up to the threshold.The location of the doped ions in the crystals is analyzed by combining the...