Development of BSO (Bi4Si3O12) crystal for radiation detector

Abstract

Colorless and crack-free single crystals of bismuth silicate (Bi4Si3O12, BSO) scintillators have been grown by the vertical Bridgman method. Some segregation phases have been found to form on the surface and at the top of the crystals grown from both stoichiometric and off-stoichiometric melt compositions. The excitation and emission spectra are similar to BGO. The light output is 20% of BGO, giving energy resolution of 32% for 662 keV γ-rays (137Cs). The decay constants are 2.4 ns (for 6% of intensity), 26 ns (12%) and 99 ns (82%). The radiation hardness against 60Co γ-rays was found about 105–106 rad at the emission peak of 480 nm for undoped and it was almost negligible up to 107 rad for 0.2 at.% Ce doped crystals. We have also achieved a considerable improvement in the growth of large size crystals, offering the possible application in γ-ray detectors at high energies. Clear blocks with transverse/longitudinal dimensions as large as 25 mm/200 mm were produced with good reproducibility. The pulse height uniformity along the longitudinal axis is within ±2%. The scintillation characteristics are similar to those of small crystals.