limit fixed by the energy gap of the compound. Thus infrared filters and selective narrow-band filterdetector combinations can be constructed to operate anywhere within the spectral range of the material.
ABSTRACTThe importance of the surface properties of zinc silicate phosphor to fluorescent brightness and lumen maintenance has been demonstrated. A phenomenological theory is developed which accounts qualitatively for some of the changes that occur during lamp burning. Inherent in this theory is the concept of a high-temperature surface phase which is a part of the zinc silicate crystal. The surface phase may be retained at room temperature by rapid quenching, but if the phosphor is cooled slowly the surface phase dissociates, probably into its constituent oxides. As a result Mn 2 § can be oxidized, and Zn ~ § can be reduced either by vacuum firing or by photolysis by u.v. light. Metallic zinc is produced as a consequence of lamp burning and it amalgamates with mercury. The zinc atoms on the phosphor surface act as vapor traps for mercury and cause it to distribute itself over the surface, probably as tiny droplets. The oxidation of Mn ~ § and the reduction of Zn ~ § can be prevented by formation of a protective layer on the phosphor surface, e. g. ZnSb20,. It is thought that the surface properties of zinc silicate phosphor, particularly those which affect the extent and perfection of a protective coating, greatly influence the quality of lamps produced by identical procedures.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.215.225.9