Optimization of scintillation performance via a combinatorial multi-element co-doping strategy: Application to NaI:Tl

A combinatorial approach where doped bulk scintillator materials can be rapidly optimized for their properties through concurrent extrinsic doping/co-doping strategies is presented. The concept that makes use of design of experiment, rapid growth, and evaluation techniques, and multivariable regression analysis, has been successfully applied to the engineering of NaI performance, a historical but mediocre performer in scintillation detection. Using this approach, we identified a three-element doping/co-doping strategy that significantly improves the material performance. The composition was uncovered by simultaneously screening for a beneficial co-dopant ion among the alkaline earth metal family and by optimizing its concentration and that of Tl+ and Eu2+ ions. The composition with the best performance was identified as 0.1% mol Tl+, 0.1% mol Eu2+, and 0.2% mol Ca2+. This formulation shows enhancement of energy resolution and light output at 662 keV, from 6.3 to 4.9%, and from 44 000 to 52 000 ph/MeV, respectively. The method, in addition to improving NaI performance, provides a versatile framework for rapidly unveiling complex and concealed correlations between material composition and performance, and should be broadly applicable to optimization of other material properties. (C) 2015 AIP Publishing LLC.