Lawrence Berkeley National Laboratory

At the High-throughput Discovery of Scintillator Materials Facility at Lawrence Berkeley National Laboratory, scintillators are synthesized by solid-state reaction or melt mixing, forming crystalline powders. These powders are formed in various granularity and the crystal grain size affects the apparent luminosity of the scintillator. To accurately predict a ?full-size? scintillator?s crystal luminosity, the crystal luminosity as a function of crystal granularity size has to be known. In this study, we examine Bi4Ge3O12 (BGO), Lu2SiO5:Ce (LSO), YAlO3:Ce (YAP:Ce), and CsBa2I5:Eu2+ (CBI) luminosities as a function of crystalline grain size. The highest luminosities were measured for 600- to 1000-?m crystal grain sizes for BGO and LSO, for 310- to 600-?m crystal grain sizes for CBI, and for crystal grains larger than 165?m for YAP:Ce. Crystal grains that were larger than 1 mm had a lower packing fraction, and smaller grains were affected by internal scattering. We measured a 34percent decrease in luminosity for BGO when decreasing from the 600- to 1000- ?m crystal grain size range down to the 20- to 36-?m range. The corresponding luminosity decrease for LSO was 44percent for the same grain size decrease. YAP:Ce exhibited a luminosity decrease of 47percent when the grain size decreased from the 165- to 310-?m crystal grains to the 20- to 36-?m range, and CBI exhibited a luminosity decrease of 98percent when the grain size decreased from the 310- to 600-?m crystal grain range to the 36- to 50-?m range. We were able to very accurately estimate full-size crystal luminosities from crystalline grains that are larger than 90 ?m.