【作者】 王佳；

【导师】 杨春晖；

【作者基本信息】 哈尔滨工业大学 ， 无机化学， 2006， 硕士

【摘要】 采用提拉法生长了两种不同[Pb]/[W]比(1.01,1.02)的PbWO4晶体、三种不同的氟掺杂浓度(150×10-6,250×10-6,400×10-6)的PbF2:PWO晶体,和与Nb(500×10-6): Mo(1000×10-6): PWO对比的La(500×10-6): PWO和La(500×10-6): Mo(1000×10-6): PWO晶体。研究掺杂对PbWO4晶体光学性能的影响。紫外透射光谱结果表明:富铅PbWO4晶体、掺氟PbWO4晶体与纯PbWO4晶体的吸收边基本一致,而镧掺杂、镧钼双掺和铌钼双掺使晶体的吸收边发生不同程度的红移;Pb:W=1.02的晶体在420nm处的透过率好于Pb:W=1.01的晶体和纯的PbWO4晶体,镧掺杂、铌钼双掺以及氟掺入量增大使透过率增强,镧钼双掺对该处的透过率没有改善。拉曼光谱证实晶体的结构为体心四方结构。Pb、La、Nb掺杂离子占据VPb,使得与Pb2+振动有关的谱线展宽并发生频移,Mo、F离子分别占据钨离子和氧离子的位置,使与WO24-基团外模振动有关的谱线展宽频移。在XRD图谱中未出现新的衍射峰,但是峰的强度和位置发生了变化,说明掺杂改变了晶格参数:过量的铅占据VPb位置,使晶胞体积增大;铌离子占据铅离子位置,氟离子和钼离子分别占据氧离子和钨离子位置,使氟掺杂和铌钼双掺PWO晶体晶胞体积变小。采用密度泛函理论的平面波赝势方法计算了纯钨酸铅晶体、氟掺杂PWO晶体和掺镧PWO晶体的能带结构、态密度和光学性质,与实际的测试结果进行了比较,研究二者的联系。计算结果表明,几种掺杂剂的掺入使晶体的能带结构、态密度和光学性能都发生了变化,通过Final energy确定了掺镧钨酸铅晶体中镧离子和铅空位的最佳占位。对比镧掺杂和纯PWO晶体的紫外光谱和吸收谱,两者可以相互说明。富铅、镧掺杂和铌钼双掺可以提高晶体在420nm处的透过率,理论计算结果和实际结果可以相互验证。更多还原

【Abstract】 In this paper, two different Pb doped PbWO4 crystals with various Pb/W ratios (1.01, 1.02), three PbWO4 crystals with different PbF2 doped concentrations (150×10-6, 250×10-6, 400×10-6), and as with Nb(500×10-6): Mo(1000×10-6): PWO for comparison, La(500×10-6): PWO, La(500×10-6): Mo(1000×10-6): PWO crystals were grown by Czochralski method. The influence of impurities on the crystal optical property were investigated.Ultraviolet spectrum revealed: Pb doped PWO, F doped PWO and pure PWO crystals have the same absorption edge, but the La doped, Nb5+-Mo6+ co-doped, La3+-Mo6+ co-doped make it shift to the longer wavelength; the impurity ions influence the transmittance of PWO in 420nm, PWO crystal with [Pb]/[W]=1.02 is better than [Pb]/[W]=1.01 and pure crystal, the La3+ doped, Nb5+-Mo6+ co-doped PWO and with the higher F doped level decreased the 420nm absorption, but the La3+-Mo6+ co-doped crystal doesn’t improve it.All kinds of PWO crystals showed the body-centered tetragonal structure in the Raman spectra. The peak related to Pb vibration was broadened due to Pb, La, Nb occupying the VPb position; For Mo and F doping, respectively, occupy the W and O position make the outer model of WO42- groups broadened.There were no new peaks in the doped-crystal X ray diffraction patterns, but the intensity and the position of peak are different from pure one, so the doped ions altered the lattice parameters: Pb2+ occupy the VPb position maked the lattice volume increase, but the PbF2 and Nb-Mo co-doped are opposite due to Nb5+, F-, Mo6+ occupying the Pb2+, O2-, W6+ position respectively.At the same time, the plane-wave pseudopotential method of Density Functional Theory is used to study the energy band structure, the densities of states and optical properties of pure PWO and doped PWO crystals.Compared with the analysis result, research their connectivity. Calculation results showed that those impurities influnced the energy band structure, the densities of states and optical properties of pure PWO crystal. Through the Final energy, the positions of La3+ and VPb in La: PWO crysal are known. Compared the UV更多还原