Summary

that shown by Rabatin and Gillooly (15) to be charac-teristic of Mn 3+. Another qualitative indication of this mechanism was the significant green fluorescence de-veloped after only air heat-treatments in preparations where small amounts of Si 4+ or Ge 4+ were substi-tuted for Ga 3+. This probably resulted from the tetra-valent cations forcing more of the manganese into the divalent state in order to balance the electrostatic charges. Jagodzinski and Saalfeld (4) have shown that va-cancies are distributed only over octahedral sites in MgA1204. If it is assumed that this is also the case for MgGa204, and that the population of Mg 2+ ions in octahedral sites is about 0.84 at 1400 ~ (2), then the optimum phosphor composition can be approxi-mated as follow