Research Of Properties Of Doped Lead Tungstate Crystal And Theoretical Calculation Of Density Function

In order to improve the optical properties of Lead Tungstate (PbWO4, PWO) crystal, the preparation of crystal has been extensively researched and the doping technique has been widely applied. In this paper, the growth technique of high-quality and doped PWO crystals had been taken through theoretical analysis and practical conformation by Czochralski method, and the optical properties of doped PWO crystals had been studied.The structure of Sm:PWO, Y:Zn:PWO, La:Zn:PWO and Yb:Zn:PWO crystals were studied by the means of XRD and Raman spectra. In our doping concentration range, Sm3 + would occupy the W6+ site firstly, then occupy Pb2 + site. Y3 +, La3 + and Yb³⁺ would occupy Pb2 + Site, Zn2 + would occupy space location. The crystal structure of doped PWO crystal was not changed and the lattice constants changed slightly.The transmittance and emission spectra indicated that, Sm³⁺ doping could reduce the transmission intensity, make the absorption edge shift to longer wavelength, Sm³⁺ ions had their own absorption peaks. Sm³⁺ ions had competitive effects with PWO matrix in luminescence, which restraining the intrinsic luminescence of PWO had concentration quenching effect.Y³⁺ and Zn²⁺ ions doping could increase the transmission intensity, with Zn²⁺ concentration enhancing, transmission intensity decreased firstly, then increased, the absorption edge shifted to shorter wavelength, this can be explained to the formation of defect clusters betweenY³⁺ and crystal defects or between Zn²⁺ ions and crystal defects, they present competition at the same time. Y³⁺ ions incorporation could sensitize the blue luminescence of negative group, so did the Zn²⁺ ions doping.The results of La:Zn:PWO and Yb:Zn:PWO displaied that doped crystals had little VPb″和VO··, absorption edge shifted to shorter wavelength, La³⁺ dopants had a strong compensation capability with VPb″, Yb³⁺ dopants were on the contrary. The valence change of element Yb might affect transmission performance. There was abnormal strong luminescence in Yb:Zn:PWO crystal, besides Yb³⁺ ions affected the disturbance created by Pb²⁺ ion to (WO4) 2- group just like La³⁺ ions, it might have a relationship with 4f13 shell of Yb³⁺ ions.Calculation of Y:Zn:PWO crystal in density functional theory shown: lattice parameters and volume of doped crystal became smaller after structure optimization. Structure band and density of states displaied that, the dopant Zn²⁺ ions could not only compensate excess charge in crystals, but formed bonding with O atom, however, Y³⁺ ions just only compensated the charge. The energy difference between conduction band and valence band was higher than that of pure PWO crystal, energy of electronic transitions increased, which responded to absorption edge shifting to shorter wavelength of Y:Zn:PWO crystal in transmission spectra.Through theoretical calculation, we can understand the affecting mechanism of dopants, different dopants have different impacts and so do different doping concentrations of the same dopant. Theoretical calculation may certificate the experimental results, make the theory and experiment achieve integration.