Preparation And Research On Optical Properties Of The Ca_xBa_1-xNb₂O₆ Thin Films

CaxBa1-xNb2O6(CBN) crystals with the structure of the tetragonal tungsten bronze(TTB) are provided with the excellent piezoelectric, dielectric, ferroelectric, electro-optic, photorefractive properties. The Curie temperature of CBN crystals is about 200 K higher than the familiar SaxBa1-xNb2O6(SBN) crystals. so that its application scopes are expanding. It is particularly important that the preparation and research on properties of CBN thin films because of the miniaturization of devices. There is less research on preparation and properties of CBN thin films. Particularly, the preparation of CBN thin film by sol-gel method has not been reported. In this paper, the CBN thin films are prepared by sol-gel method successfully and the optical properties of it are studied. The main results are as follows:1、The optimum process conditions of CBN thin films by sol-gel method are obtained. The effects of CA/EG and p H value on the stability of the precursor sol are investigated. The results showed that the precursor sol is formed at p H =7 and the optimum mass ratio of citric acid and ethylene alcohol is 40:60. By annealing at 800℃ for 1h, single phased CBN thin films are prepared when the mass ratio of citric acid and ethylene alcohol is 100:0.2、The lattice constants of different components and different doping amounts are obtained by fitting and computing the XRD patterns of CBN thin films. The results agreed with known lattice constants. It is found that the unit cell volume decreased with the increase in doping amounts.3、The refractive index of different CBN thin films is obtained by researching its transmittance spectrum and all of them are accord with Sellmeier dispersion relation. The results of optical band gap reveal small changes.4、The positions of the peak shift to higher angle by researching the XRD patterns of Nd-doping CBN-30 thin films. It shows that the Ba atoms is replaced by Nd atoms which entering the unit cell and that makes the unit cell volume decrease. The optical absorption is blue shifted with the increase in doping amounts and the optical band gap largen. It shows that Nd-doping has great influence on the optical properties of CBN-30 thin films.