Synthesis and Formulation of Inorganic Phosphors

The manufactnring process for the important zinc and cadmium sulfide phosphors involves precipitation of the sulfide from purified salt solutions, e.g. the snlfate, with hydrogen snlfide. For ZnS Cu, the copper activator is added, as a readily decomposed derivative, to the sulfides and after grinding the components are fired in fnmaces at temperatures in the range 800-1200 °C. ZnS Ag, the bine phosphor nsed in CRTs, is prepared by firing zinc sulfide with silver nitrate at 1000 °C, nsnally in the presence of sodinm chloride to give the co-activating chloride ions. 

Oxygen-dominant phosphors are made by a solid-state reaction between the intimately mixed components of the phosphor, generally the oxides or oxide forming derivatives, at 500-1500 °C. For instance, Y2Al3Ga20j2 Tb + is made by mixing stoichiometric qnantities of the oxides, containing 5-7 mol% of terbium, with 20% BaFj in ethanol. The mixture is dried and then fired for 2 h at 1500 °C. The resultant flnx is washed with 20% nitric acid. 

Strontium thiogallates, such as SrGa S iCe, are produced by Mug a mixture of high purity sulfides, containing 4 mol% Ce + in a stream of hydrogen sulfide gas at 900-950 °Cfor2h. 

Orthosilicates for use in CRT and projection TV tubes are made by solid-state reactions, e.g. Zn SiO Mn2+ by firing a mixture of ZnO, SiO and MnCOj at 1200°Cfor2h. 

These are selected syntheses from a whole range and the limited details are only intended to provide an insight into the types of synthetic methods that are employed. Any reader wishing to have further information should consult the book edited by Gunter Buxbaum as this contains more details and a list of primary reference sources for the methods of manufacture.  

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