Growth and characterization of ions doped lead tungstate scintillation crystals by using novel multi-crucible temperature gradient system

摘要

PbWO4 crystals and BaF2: PbW04 crystals are grown by a novel multi-crucible temperature gradient system developed by our selves.Utilizing a topical partial heating method,this system can form a topical partial high temperature in its hearth. This special system can melt raw material in step by step but not fully melt the raw material together in the crucible. The advantage of this novel method is that there would be solid obstruct left on the melt in the procedure of the crystal growing up. The left obstruct could prevent the volatiliza tion of the component in the melt.Hence it is helpful for the composition homogenization in the crystal. The system also offers a sustain ing device for multi-crucible and can growth many crystals. The optical properties and scintillation properties of the two kind crystals are studied. The results reveal that the ions doping improves the scintillation properties of the crystal. The transmittance spectra show that the transmittance of BaF2: PbWO4 crystals are better than that of PbW04 crystals.For the PbWO4 crystals,their absorption edge is at 325 run,and their maximum transmittance is 68%.While for the BaF2: PbW04 crystals,their absorption edge is at 325 run and their maximum transmittance is upto 76%.For The studied of X-ray excited luminescence spectra shows that the luminescence peak is at 420 run for the samples of PbWO4 crystal while the luminescence peak is at 430 nm for the samples of BaF2: PbW04 crystal respectively. Analyzing these scintillation properties,we find that the Vpb3+ and Vo- defects do harm for the optical properties of the crystal.Ions do ping method could reduce the defect concentration and improving its illumination performance of the crystal.Specially,the doped F- ions in O2- site can induce the aberrance of the [ WO4 ]2- tetrahedron and form [ WO3F]-tetrahedron which has more active blue light yield,thus improve the light yield of the crystal. The improved light yield of BaF2: PbWO4 crystals is valuable for the medical diagnosing instru ment PET and CT with high resolving power.