| Due to the small size of nano materials in one-dimensional space, crystallites are influenced by the presence of significant numbers of surface atoms and by the quantum confinement of the electronic states providing novel properties compared with their corresponding bulk phases, this is particularly true in the case of luminescent materials since emission lifetime, luminescence quantum efficiency and concentration quenching were found to strongly depend on the particle-size in the nanometer range. Among the fluoride compounds, Ca F2 is an attractive material because of its stability and non-hygroscopic behavior. Recently there are a lot of researches on the synthesis and properties of rare earth doped fluoride, especially in laser research. Nd3+ ion with wide absorption band, low pumping threshold, large absorption and emission cross section is an excellent performance of the gain medium. In laser applications, Nd3+ ion is the earliest and most widely used. It can be used as the activation of more than 100 kinds of matrix materials. Nd3+ ion has a larger absorption at around 808 nm, which can realize laser output at 1064 nm. Co-doped Y3+ ions can form [Nd3+-Y3+] activation center, and can replace the the original [Nd3+-Nd3+] cluster structure, the formation of new [Nd3+-Y3+] clusters having more or less complicated structures, rich in the crystal strcture, which can reduce the concentration quenching or prevent the energy transfer caused by rare earth ions and some cross relaxation, thus to improve the optical performance has the obvious effect, can increase the emission line width and can realize the continuous wave operation at 1.06?m. In this paper, wet chemical precipitation method and two kinds of drying methods were used to synthesis Nd, Y:Ca F2 nano-powders, mainly to explore the relations between different reaction conditions and the structure and properties of powders. The major points of this work were summarized as follows:1. Wet chemical precipitation method was used to synthesis Nd, Y:Ca F2 nanoparticles. XRD, FE-SEM, particle size analyzer, infrared spectro-meter and absorption spectroscopy were both used to measure crystal structure, morphology, dispersion, particle size distribution and optical properties. The results of the study found that, we obtained the similar spherical morphology, the grain size is in the range of 18-25 nm, good dispersion, the crystallization is not complete, and there are many impurities(NO3-, OH-).2. Different Nd, Y doping content of Ca F2 nano powder were studied, when Y3+ doping 2at %, particle dispersion is best and the particle size distribution is the most narrow when Nd3+ with 4 at% dopants. When co-doped with Y3+, with the increase of Y3+ dopants, the lattice parameters and the FWHM increased gradually, indicating the crystallinity decreased and crystal defect increased. The results of ICP showed that, Nd3+ ion is 1.98at%, Y3+ ion is 3.78at% in 2%Nd,4% Y:Ca F2, which shows that the rare earth ion doped well into the Ca F2 lattice.3. Effects of different annealed temperature on the structure and properties of Nd,Y:Ca F2 nano powder was studied. At low temperature(200?), the grain size changes little, when the temperature continues to rise, the particles grow up, the morphology of the boundary becomes more clearly, the impurity ions(NO3-, OH-) were more and more less, and the absorption strength exhibited a rising trend. But when the temperature reached 800?, the absorption intensity decreased and the impurity ion exclusion did not change much compared with 600?. Both considering the particle size and impurity removal, the optimum calcination temperature is 600?.4. Because of the wet gel is easily bridged adhesion in the drying process and the occurrence of clusters. Azeotropic distillation was used to remove water in maximize. Azeotropic distillation method showed that the agglomeration degree was significantly reduced, we obtained uniform particle size distribution, and the TG-DSC, FTIR and absorption spectra showed that the dehydration effect is much better than the direct drying method... |
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