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As a valuable material for the detecting of γ-ray, PbWO4 and BaF2:PbWO4 crystals were grown
by a novel multi-crucible temperature gradient system developed by ourselves. Utilizing a topical
partial heating method, this system can form a topical partial high temperature in its hearth. Thus
this system could melt raw materials in step by step as requirement. The advantage of this 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 volatilization of the component in the melt. Hence it is helpful
for the composition homogenization in the crystal. The system also offers a sustaining device for
multi-crucibles and thus it can grow many crystals simultaneity. The optical properties and
scintillation properties of the crystals were 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 PbWO4 crystals. For the PbWO4
crystals, their absorption edge is at 325nm, and their maximum transmittance is 68%.
For the BaF2:PbWO4 crystals, their absorption edge is at 325nm and their maximum
transmittance is upto76%. The X-ray excited luminescence spectra shows that the
luminescence peak is at 420nm for the samples of PbWO4 crystal while the peak is at
430nm for the samples of BaF2:PbWO4 crystal respectively. The luminescence intensity of
the samples of BaF2:PbWO4 crystal is about two times than that of PbWO4 crystal. And their peak
shape is different for the two kind of crystal. The light yield of BaF2:PbWO4 crystals is
about 2.9 times than that of PbWO4 crystal Analyzing these scintillation properties, we find that
the VPb
3+ and VO- defects do harm for the optical properties of the crystal. Ions doping 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 instrument PET and CT with high resolving power
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