Growth And Scintillation Properties Of Dy Doped Bi₄Si₃O₁₂ Crystals

Bismuth silicate (Bi4Si3O12, BSO) is known as an excellent scintillator for various applications in high energy physics, nuclear medicine, geological prospecting and other industries. Compared with bismuth germanate (Bi4Ge3O12, BGO), BSO has much faster decay time, higher radiation hardness and lower cost. BSO is considered as one of the possible candidates for an alternative to BGO. Recent studies show that BSO crystals are excellent materials to be used in 4π electromagnetic calorimeters in the energy region of several hundreds of MeV and BSO crystals have the better performance than BGO and PWO used for dual readout. Because of the different physical properties of Bi2O3 and SiO2, including the density and melting point, compositional deviation easily occurs during the BSO crystal growing. Low light output is anather factor which limit its further application.In this paper, high quality and different concentration of Dy doped BSO crystals were grown by the modified Bridgman method and the scintillation properties were measured. There are no cracks and obvious compositional deviation in grown crystals. The crystals have about 80% transmittance in the visible region. The light yield of BSO doping with small doses of Dy3+ increased obviously and the energy resolution improved significantly compared to pure BSO. The optimized concentration of Dy2O3 is about 0.1 mol% based on our experimental results which could make the light yield to 150% of pure BSO crystal. However, high concentration of Dy doping resulted in the decrease of light yield. The luminescent mechanism shows that small doses of Dy3+ doping could sensitize the Bi3+ ions. While the concentration of Dy+ increased, the Dy+ ions became new luminescent centers by replace some Bi3+ resulted in reducing the light yield. The fluorescence spectra properties show that Dy doped BSO may emit yellow light when excited at 288 nm while Tm/Dy co-doped BSO crystal can emit white light under excited by 357 nm, they are both the promising LED phosphor.