The investigation of new phosphors, with particular reference to the pyrophosphates

There is a continuing demand for new phosphors in the fluorescent lamp industry and the initial stages of the search for suitable materials are essentially of a chemical nature. Some of the techniques used in this work are illustrated by reference to a large group of alkaline earth pyrophosphate phosphors recently developed. These materials utilize Sn 2 + or Ce 4 + as primary activator and manganese as secondary activator, and are of considerable potential application. Physical methods of analysis have proved indispensable in providing an understanding of this pyrophosphate system. By means of X-ray and differential thermal analysis the various crystal structures of the pure pyrophosphates have been studied, and the conditions for the existence of the different forms estalished. Crystal data for the more important structures are given. The relationships between the main peaks of the emission bands, crystal structures and activators are discussed. A detailed study of such systems, in which interchange of matrix metal, well-defined crystal changes, and different activators produce marked changes in the fluorescence, may prove to be of importance in developing a useful theory of luminescence in activated inorganic solids.