The possible defect models of Y^3＋：PbWO4 crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y^3＋ ions are studied by using the general utility lattice program （...The possible defect models of Y^3＋：PbWO4 crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y^3＋ ions are studied by using the general utility lattice program （GULP）. The calculated results indicate that in the lightly doped Y^3＋ ：PWO crystal, the main compensating mechanism is [2Ypb^＋ ＋ VPb^2-], and in the heavily doped Y^3＋ ：PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by YPb^＋, forming defect clusters of [2Ypb^＋ ＋Oi^2-] in the crystal. The electronic structures of Y3＋ ：PWO with different defect models are calculated using the DV-Xα method. It can be concluded from the electronic structures that, for lightly doped cases, the energy gap of the crystal would be broadened and the 420nm absorption band will be restricted; for heavily doped cases, because of the existence of interstitial oxygen ions, it can bring a new absorption band and reduce the radiation hardness of the crystal.展开更多
Y_2(p-CH_3C_6H_4COO)_6(C_(12)H_8N_2)_2, Mr=1349.08, triclinic, space group P, a=13.00(3), b=19.743(2), c=12.754(3)A, α=97.94(1), β=106.24(2), γ=91.66(1)°, V=3177(1)~3, Z=2, Dc=1.41gcm^(-3), λ(MoKα)=0.71069, ...Y_2(p-CH_3C_6H_4COO)_6(C_(12)H_8N_2)_2, Mr=1349.08, triclinic, space group P, a=13.00(3), b=19.743(2), c=12.754(3)A, α=97.94(1), β=106.24(2), γ=91.66(1)°, V=3177(1)~3, Z=2, Dc=1.41gcm^(-3), λ(MoKα)=0.71069, μ=18.92 cm^(-1), F(ooo)=1384, T=295K, final R=0.073 for 6504 observed reflections with Ⅰ>36(Ⅰ). There are two nonidentical binuclear molecules with different bridging connection patterns in a cell. One has four bridging carboxyl groups bound two Y(Ⅲ) ions and another only has two. The Y-Y distance is 4.196 for the former and 5.302 for the latter respectively.展开更多
Fluorescence decay curves of the ^3P0 and ^1D2 manifolds in Pr^3＋ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifeti...Fluorescence decay curves of the ^3P0 and ^1D2 manifolds in Pr^3＋ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifetimes of the manifolds calculated on the basis of the modified J-O theory, the main mechanisms for the fluorescence quenching of the manifolds were analyzed. The multi-phonon relaxation and the cross-relaxation energy transfer are the major reasons for the fluorescence quenching of the ^3P0 and ^1D2 manifolds, respectively. The Inokuti-Hirayama model was used to analyze the fluorescence decay curve of the ^1D2 manifold and the cross-relaxation of dlpole-dipole interaction was confirmed. Consequently, the ^3p0 manifold is more favorable as an upper laser level than the ^1D2 manifold.展开更多
The effect of Y and Sb co-doping on the luminescence property of PbWO 4 crystals has been investigated. Compared with undoped PbWO4, the transmittance and emission peak intensity of Y∶Sb∶PbWO 4 crystals were obvious...The effect of Y and Sb co-doping on the luminescence property of PbWO 4 crystals has been investigated. Compared with undoped PbWO4, the transmittance and emission peak intensity of Y∶Sb∶PbWO 4 crystals were obviously improved. In addition, its transmittance cutoff wavelength and emission peak shifted to the shorter one. The mechanism of effect of Y and Sb on the transmittance spectra was briefly discussed. The light yield of Y∶Sb∶PbWO 4 crystals was 25p.e./MeV, which was two times of that of undoped PbWO 4. Our experiments showed that Y and Sb co-doping was a selectable method to improve the luminescence property of PbWO 4.展开更多
Er^3＋ ：Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 ＋ ions in th...Er^3＋ ：Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 ＋ ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.展开更多
The measurements of light yield of PbWO<sub>4</sub> crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with no...The measurements of light yield of PbWO<sub>4</sub> crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with normal radioactive sources is proposed and the measurements for severalPbWO<sub>4</sub> samples produced by Beijing Glass Research Institute are reported.展开更多
Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re...Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re∶GdYCOB single crystals growth were synthesized by multistage solid phase reaction method.Re∶GdYCOB single crystals were grown by Czochralski technique.The pulling rates are 0.5-2mm/h and the rotation rates are 10-30r/min.Usually 65-75% polycrystalline materials can be transformed into good quality single crystals under our growth conditions. The structures of some as grown Re∶GdYCOB single crystals were measured by using a four circle diffractometer.The results measured show that the space group of the crystals is C 3 s Cm.The determined lattice constants of 8 at% Nd doped Ca 4YO(BO 3) 3 single crystal are a =0.8076nm, b =1.6020nm, c =0.3527nm , β =101.23°.展开更多
The luminescent properties of PbWO 4∶Gd 3+ were studied. The luminescence of Gd 3+ in PbWO 4∶Gd 3+ was quenched. It is possible that the excitation states of Gd 3+ locate in the conduction band...The luminescent properties of PbWO 4∶Gd 3+ were studied. The luminescence of Gd 3+ in PbWO 4∶Gd 3+ was quenched. It is possible that the excitation states of Gd 3+ locate in the conduction band of PbWO 4 crystal. The luminescent intensity of the green and the blue band of PbWO 4 emission increases by doping with about 0 005% and 0 01% (molar fraction) Gd 3+ respectively. Mechanism of this enhancement of PbWO 4∶Gd 3+ luminescence is probably due to energy transfer from Gd 3+ to PbWO 4 host in the crystal. The PbWO 4 doped with low concentration of Gd (about 0 005%～0 01%) is a good scintillating material.展开更多
文摘The possible defect models of Y^3＋：PbWO4 crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y^3＋ ions are studied by using the general utility lattice program （GULP）. The calculated results indicate that in the lightly doped Y^3＋ ：PWO crystal, the main compensating mechanism is [2Ypb^＋ ＋ VPb^2-], and in the heavily doped Y^3＋ ：PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by YPb^＋, forming defect clusters of [2Ypb^＋ ＋Oi^2-] in the crystal. The electronic structures of Y3＋ ：PWO with different defect models are calculated using the DV-Xα method. It can be concluded from the electronic structures that, for lightly doped cases, the energy gap of the crystal would be broadened and the 420nm absorption band will be restricted; for heavily doped cases, because of the existence of interstitial oxygen ions, it can bring a new absorption band and reduce the radiation hardness of the crystal.
文摘Y_2(p-CH_3C_6H_4COO)_6(C_(12)H_8N_2)_2, Mr=1349.08, triclinic, space group P, a=13.00(3), b=19.743(2), c=12.754(3)A, α=97.94(1), β=106.24(2), γ=91.66(1)°, V=3177(1)~3, Z=2, Dc=1.41gcm^(-3), λ(MoKα)=0.71069, μ=18.92 cm^(-1), F(ooo)=1384, T=295K, final R=0.073 for 6504 observed reflections with Ⅰ>36(Ⅰ). There are two nonidentical binuclear molecules with different bridging connection patterns in a cell. One has four bridging carboxyl groups bound two Y(Ⅲ) ions and another only has two. The Y-Y distance is 4.196 for the former and 5.302 for the latter respectively.
文摘Fluorescence decay curves of the ^3P0 and ^1D2 manifolds in Pr^3＋ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifetimes of the manifolds calculated on the basis of the modified J-O theory, the main mechanisms for the fluorescence quenching of the manifolds were analyzed. The multi-phonon relaxation and the cross-relaxation energy transfer are the major reasons for the fluorescence quenching of the ^3P0 and ^1D2 manifolds, respectively. The Inokuti-Hirayama model was used to analyze the fluorescence decay curve of the ^1D2 manifold and the cross-relaxation of dlpole-dipole interaction was confirmed. Consequently, the ^3p0 manifold is more favorable as an upper laser level than the ^1D2 manifold.
文摘The effect of Y and Sb co-doping on the luminescence property of PbWO 4 crystals has been investigated. Compared with undoped PbWO4, the transmittance and emission peak intensity of Y∶Sb∶PbWO 4 crystals were obviously improved. In addition, its transmittance cutoff wavelength and emission peak shifted to the shorter one. The mechanism of effect of Y and Sb on the transmittance spectra was briefly discussed. The light yield of Y∶Sb∶PbWO 4 crystals was 25p.e./MeV, which was two times of that of undoped PbWO 4. Our experiments showed that Y and Sb co-doping was a selectable method to improve the luminescence property of PbWO 4.
文摘Er^3＋ ：Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er^3 ＋ ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.
基金The project supported by the Science Foundation of Beijingthe Foundation of Science College of Tsinghua University
文摘The measurements of light yield of PbWO<sub>4</sub> crystals with normal methods may haverelatively large errors because the crystals have a low light yield.Therefore,a single photoelec-tron method with normal radioactive sources is proposed and the measurements for severalPbWO<sub>4</sub> samples produced by Beijing Glass Research Institute are reported.
文摘Growth and morphology of neodymium or ytterbium doped calcium gadolinium yttrium oxoborate (Re∶Ca 4Gd x Y 1- x O(BO 3) 3(Re∶GdYCOB)Re =Nd,Yb; x =0-1)were systematically studied. Polycrystalline materials used for Re∶GdYCOB single crystals growth were synthesized by multistage solid phase reaction method.Re∶GdYCOB single crystals were grown by Czochralski technique.The pulling rates are 0.5-2mm/h and the rotation rates are 10-30r/min.Usually 65-75% polycrystalline materials can be transformed into good quality single crystals under our growth conditions. The structures of some as grown Re∶GdYCOB single crystals were measured by using a four circle diffractometer.The results measured show that the space group of the crystals is C 3 s Cm.The determined lattice constants of 8 at% Nd doped Ca 4YO(BO 3) 3 single crystal are a =0.8076nm, b =1.6020nm, c =0.3527nm , β =101.23°.
文摘The luminescent properties of PbWO 4∶Gd 3+ were studied. The luminescence of Gd 3+ in PbWO 4∶Gd 3+ was quenched. It is possible that the excitation states of Gd 3+ locate in the conduction band of PbWO 4 crystal. The luminescent intensity of the green and the blue band of PbWO 4 emission increases by doping with about 0 005% and 0 01% (molar fraction) Gd 3+ respectively. Mechanism of this enhancement of PbWO 4∶Gd 3+ luminescence is probably due to energy transfer from Gd 3+ to PbWO 4 host in the crystal. The PbWO 4 doped with low concentration of Gd (about 0 005%～0 01%) is a good scintillating material.
