Investigation On Crystal Growth And Upconversion Luminescence Of Er/Yb Doped 12CaO·7Al2O3

As the social development has increased the demand for energy, meanwhile investigation on the crystals and optical application were also increased. 12CaO·7Al2O3(short for C12A7) single crystal has special structure, and has extraordinary application value in optical field. The main content of this dissertation includes the study of C12A7 single crystal growth parameters and upconversion property of Er3+/Yb3+ codoped C12A7.C12A7 single crystals have grown in the method of Czochralski. And we have investigated The external factors include growth technical parameters, annealing process parameters, oxygen content, crucible and the internal factor includ the syntheses parameters of C12A7 polycrystalline powder, which can effct the quality of the single crystal have been studied. Then we obtained the optimum parameter, rotating rate was 10 R.P.M., lifting speed was 0.8 mm/h, shouldering temperature gradient was 3 ℃/h, annealing processes was 30 ℃/h to 90 ℃, then 60 ℃/h to room temperature, oxygen concentrations was controlled at 1%, and Ir crucible was used. We used over-stoichiometric of Al2O3 which was 1 mol% excess.C12A7 single crystal structure was analyzed by a series of spectral analysis. The band gap tested by ultraviolet-visible absorption spectra was 4.25 eV. Raman scattering spectra showed the highest phonon energy was about 880 cm-1. The infrared absorption spectrum had two peaks between 600 cm-1 and 850cm-1 which belonged to the frame structure of C12A7.The mechanism of upconversion luminescence of Er3+/Yb3+/C12A7 and the factors affecting upconversion luminescence had been explored. The emission of Er3+/Yb3+/C12A7 were mainly green emission that belong to 2H11/2,4S3/2â†'4I15/2 and red emission belong to 4F9/2â†'4I15/2. Concentration of Er3+, OH- and Yb3+, the emission center and quench center and sensitization agent, which were all factors that can influence the upconversion emission. Er3+ mainly affected upconversion luminescence by cross relaxation and changing the band gap of the material. OH- could enhance non-radiative transition that can weak the intensity of green light, and fluorescence intensity ratio had been used as a probe to tested out the oncentration of OH- which was 1.7×1018cm-3. Yb3+ affected upconversion emission by Cross-Relaxation between itselves, which could determine the pump efficiency.Upconversion emission spectrum was tested at different temperatures and Er3+/Yb3+/C12A7 applying on temperature sensor was discussed. The temperature sensitivity coefficient S of Er3+/Yb3+/C12A7 polycrystal and single-crystal were 1124.81 and 1122.69 respectively. Compared with polycrystal, Er3+/Yb3+/C12A7 single-crystal has more application value in the application of temperature sensor.