Luminescence, energy transfer properties of Tb3+/Gd3+-coactivated oxyfluoride borogermanate scintillating glasses

Gd3+-, Tb3+/Gd3+-coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.35-6.61 g/cm3 were prepared by a melt-quenching method. The luminescent and energy transfer properties were studied by transmittance, photoluminescence and X-ray excited luminescence (XEL) spectra. The total content of rare-earth oxide and fluoride is as high as 49 mol% in oxyfluoride borogermanate glasses, which are necessary to ensure their density up to 6.61 g/cm3. Energy transfer efficiency and mechanism from Gd3+ to Tb3+ were determined, and the corresponding critical distances for both Gd3+-Tb3+ and Tb3+-Tb3+ ion pairs were calculated, respectively. The optimal concentration of Tb3+ ions in dense oxyfluoride borogermanate glasses excited by both ultraviolet light and X-ray excitation were also determined. The integral scintillation efficiency of Tb3+-activated borogermanate scintillating glass was found to be about 26.9% of the standard Bi4Ge3O12 (BGO) scintillating crystal.