The pink coloration often found in calcium halophosphate phosphors has been found to be associated with the presence of an impurity phase of ~(Ca, Mn)3(P04)2 which forms on partial degradation of the phosphor. The identification, preparation, properties, and mode of formation of this impurity are described. The pink coloration is due to trace amounts of Mn +3. Because Mn +3 absorbs strongly in both the visible and ultraviolet regions, it has a deleterious effect on phosphor brightness. * Initial chloride content 0.62 w/o. ** Chloride loss limited due to the low amount of Ca~P207 initially present.

Total chemical analysis of luminescent apatite together with quantitative x-ray diffraction analysis for secondary phases have made it possible to delineate the maximum permissible nonstoichiometry. Based on the accuracy of the various methods and expressed as a deficiency of calcium, the extent of nonstoichiometry is less than the absence of one calcium in every 380 calcium sites. Quantitative experimental evidence is also presented to support the hypothesis for charge compensation of antimony by a corresponding oxygen substitution at halogen sites.

A double crucible technique has demonstrated that the principal phosphor forming reactions may involve particle-particle interaction between Ca~P207 and CaF2 leading to direct formation of apatite and POF3. The POF3, or vapors of similar composition, react with CaCO~ also forming apatite. The transport of vapors containing fluorine, phosphorus, oxygen, and antimony has been demonstrated. Activation of the phosphor above 1000~ occurs by a reaction of Sb204 vapor with apatite.