Luminescence of Three Forms of Zinc Orthophosphate:Mn'

Three forms of zinc orthophosphate:manganese have been found. The a form cor-responds in x-ray diffraction pattern to the published values. The luminescence is green, the peak wavelength being 5540 A. It is produced when manganese concentrations arc below 1 mole per cent, or when higher concentrations are not heated above 700 ~ The fl form has a red luminescence with a peak at 6380 A. This formation occurs at manganese concentrations above 1 mole per cent and firing temperatures above 800 ~ The-y form may be produced by additions of magnesium orthophosphate above 3 mole per cent. The emission is similar to the ~ form with a peak at 6320 A, and of somewhat lowered intensity