Abstract: In this work, we grew two types of Bi₄Ge₃O₁₂ (BGO) crystals in different temperature gradient by
Bridgmen-Stockbarger technology and compared the optical transmissions and energy resolutions of the two types of BGO crystals before and after
ultraviolet irradiation. It was found that the optical transmissions and energy resolutions of the two types of BGO crystals are similar before
UV-irradiation. After UV-irradiation the optical transmissions at 480nm of the first type of BGO crystals which were grown in high temperature
gradient cut down about 20% and their energy resolutions obviously changed bad from about 12% to 18%. But the optical transmissions and energy
resolutions of the second type of BGO crystals which were grown in low temperature gradient keep unchanged on the whole. After 250℃/4h
annealing, the optical transmissions and energy resolutions of the second type of BGO crystals can completely be recovered. Whereas the optical
transmissions and energy resolutions of the first type of BGO crystals can’t completely be recovered until through 800℃/8h annealing. The
thermoluminescence curves of the two types of BGO crystals show that there is a luminescence peak at 85℃ for second type of BGO crystal,
whereas for the first type of BGO crystals, besides at 85℃, there are also two luminescence peaks at 130℃ and at 170℃ which
may show that there exist defects with deeper traps in the first type of BGO crystals. The reason for the difference between the first and second type
of BGO crystals may be that if the temperature drop dawn too fast during crystal growing, the defects in the melt can not spread out to the surface and so the
defects easily exist in the first type of BGO crystals.

Key words: Bi₄Ge₃O₁₂crystals, temperature gradient, radiation damage