Manganese-Activated Luminescence in SrAl[sub 12]O[sub 19] and CaAl[sub 12]O[sub 19]

Manganese‐activated and phosphors have been prepared under oxidizing and reducing conditions, and by direct cation exchange. The red emission of oxidized phosphor and green emission of reduced phosphor confirm previous assignments to octahedral Mn 4+ and tetrahedral Mn 2+ , respectively. New emission bands in the yellow and orange arise from centers which are related to cation exchange, presumably the Sr 2+ or 5‐coordinated Al 3+ sites. The behavior of the various emission bands during further oxidation and reduction provides a guide to the sites on which the activator centers are located.