New Stannate Luminescent Materials

The preparation and photoluminescence properties of M_2-xEu_xSnO₄(M=Ca,Sr) phosphors have been discussed in this paper. Typically, the red Ca_2-xEu_xSnO₄ phosphors prepared through ammonia and ammonium oxalate precipitation method and the red Sr_2-xEu_xSnO₄ phosphors prepared through high-temperature solid-state method are characterized by XRD,TG,FT-IR,PL,TEM,SEM respectively. The main conclusions are as follows:The red Ca_2-xEu_xSnO₄ phosphor by the preparation of ammonia precipitation method is a novel-red phosphor. Ca_2-xEu_xSnO₄ with orthorhombic system structure consists of SnO6 octahedra which are linked by edges and the Ca2+ which are surrounded by seven oxygen ions in an arrangement of low symmetry. The Eu³⁺ ions substitute for the Ca2+ sites, not Sn4+ sites. The Ca_2-xEu_xSnO₄ phosphor morphology particles are about 200nm, however the result isn't accorded with calculation, because the sample reunite at high-temperature. The Ca_2-xEu_xSnO₄ contains two absorption bands with main peaks of 396nm and 289nm, which are attributed to f-f transitions and due to CTB, respectively. And the intensity of 289nm is lower than that of 396nm. The emission spectrum excited by 396nm originates from the transition 5D0â†'7FJ(J=0-4) of Eu³⁺ and the strongest emission line is at 617nm, originating from the transition 5D0â†'7F2 of Eu³⁺. The preparation conditions of the phosphor sample have been also carefully studied. When the pH value of precursor solution, the mol proportion of Eu³⁺, the sintering temperature, the mode of annealing is 8, 10 %, 1200 oC, slowly annealing respectively, the phosphor sample owns the maximum emission intensity of photoluminescence. The luminescence intensity of Ca_2-xEu_xSnO₄ can be significantly enhanced by co-doped with Li+ ion. The energy of Ca_2-xEu_xSnO₄ excited by 396nm is low, so it will be a promising phosphor by long wavelength UV excitation and will be applied to red phosphor of LED of emvironment protection and save of intensity.The Ca_2-xEu_xSnO₄ by ammonium oxalate precipitation is also orthorhombic system structure and the Eu³⁺ ions substitute for the Ca2+ sites. The phosphor particles are about 250nm～300nm at high-temperature. The Ca_2-xEu_xSnO₄ synthesized through ammonium oxalate precipitation also contains two absorption bands, peaking around 289nm and 396nm, with the main excitation locating at around 289nm. The main emission excited by 289nm locates at 617nm. I study the technology conditions of preparation. When the mol proportion of (NH4)2C2O4 to basics, the mol proportion of Eu³⁺, the sintering temperature, the mode of annealing are 1.2:1, 10%, 1200oC, slowly annealing respectively, it owns maximum emission intensity of photolumines- cence. The luminescence intensity of Ca_2-xEu_xSnO₄ can be significantly enhanced by co-doped with alkali metal ions, especially for Li+ ion.The red Sr_2-xEu_xSnO₄ phosphor by the preparation of high-temperature solid-state method is a novel-red phosphor too. Sr_2-xEu_xSnO₄ in which the Eu³⁺ ions substitute for the Sr2+ sites is orthorhombic system structure. The bulk of particles tested by SEM are about 100nm. The Sr_2-xEu_xSnO₄ made through high-temperature solid-state method also contains two absorption bands, 289nm and 396nm. The main excitation locates at 289nm and the main emission by excited 289nm locates at 623nm. Similarly when the mol proportion of Eu³⁺, the sintering temperature, the mode of annealing is 12%, 1200oC, slow annealing respectively, it owns maximum emission intensity of photoluminescence. By co-doped Li+ ion, the luminescence intensity of Sr_2-xEu_xSnO₄ can be significantly enhanced.In a word, the preparation conditions of three methods are simple and are flexible to be controlled, so they can be easily applied to technological production. The obtaining red phosphors have high-purity,high-stability and low exciting energy. The price of raw material of samples is cheaper than that of traditional Y2O3:Eu phosphors, then they can be produced industrially.