Highly europium-doped strontium aluminate phosphor (Sr0.88Eu0.12Al2O4) particles were prepared by microspray pyrolysis. The crystallographic sites of the doped Eu2+ ions and their local atomic coordinates were determined using a combination of Rietveld refinement and the maximum entropy method (MEM) with high-resolution synchrotron X-ray powder diffraction data. The final Rietveld refinement yielded good R factors of R-wp = 2.59% (S = 1.86) and RB = 1.08% with the following lattice parameters: a = 8.44032(7) angstrom, b = 8.81680(8) angstrom, c = 5.15551(5) angstrom, and beta = 93.3615(3)degrees. It was evident that there were two crystallographic sites for doped Eu2+ ions, namely, Eu1 and Eu2, which were located far from the Sr sites and had displacements of 0.200(7) and 0.160(8) angstrom, respectively. Comparison of the resulting local atomic coordinates of Eu1 and Eu2 revealed similar atomic configurations at both Eu sites, indicating that the emission peaks for both appeared at almost the same positions. Electron density distribution was calculated by MEM, and the results clearly showed that all the doped Eu2+ ions were introduced near Sr1 and Sr2; no other possible crystallographic sites were found. In addition, a subtle electron density between Sr2+/Eu2+ and O2- ions was observed, implying the occurrence of charge transfer between Sr2+/Eu2+ and O2- ions. (c) 2008 The Electrochemical Society.