An intelligent approach to the discovery of luminescent materials using a combinatorial approach combined with Taguchi methodology

A significant advance made in combinatorial approach research was that the emphasis shifted from simple mixing to intelligent screening, so as to improve the efficiency and accuracy of discovering new materials from a larger number of diverse compositions. In this study, the long-lasting luminescence of SrAl ₂O₄, which is co-doped with Eu²⁺, Ce ³⁺, Dy³⁺, Li⁺ and H₃BO₃, was investigated based on a combinatorial approach in conjunction with the Taguchi method. The minimal number of 16 samples to be tested (five dopants and four levels of concentration) were designed using the Taguchi method. The samples to be screened were synthesized using a parallel combinatorial strategy based on ink-jetting of precursors into an array of micro-reactor wells. The relative brightness of luminescence of the different phosphors over a particular period was assessed. Ce³⁺ was identified as the constituent that detrimentally affected long-lasting luminescence. Its concentration was optimized to zero. Li⁺ had a minor effect on long-lasting luminescence but the main factors that contributed to the objective property (long-lasting luminescence) were Eu²⁺, Dy³⁺ and H ₃BO₃, and the concentrations of these dopants were optimized to 0.020, 0.030 and 0.300, respectively, for co-doping into SrAl ₂O₄. This study demonstrates that the utility of the combinatorial approach for evaluating the effect of components on an objective property (e.g. phosphorescence) and estimating the expected performance under the optimal conditions can be improved by the Taguchi method.