Phosphors Based on Spinels

The spinel group is divided into three immiscible series, the spinel in which Bis aluminum (aluminum-spinel), the chromite (chromium-spinel) series in which B is chromium and the magnetite (iron-spinel) series, in which B is iron. 

For reasons which will become clear later, we cannot use chromium-spinels or iron-spinels as a phosphor base. Thus, we are limited to aluminum, tin and the like. We will limit our discussion to tin and gallium-based compounds, i.e.- Mga SnO and Mg2Ga04. 

Both of these materials can be activated by Mn which also forms a spinel, i.e.- Mn2Sn04. The latter as a phosphor, i.e.- Mg2GKi04 Mn , is used as the source of green light in most copsdng machines today. It is interesting to note that the cubic spinel structure is formed by a majority of dibasic cations like Mg and that many trivalent or quadrivalent cations can form oxide-based anions like stannate. aluminate, titanates, vanadates and the like. 

To prepare a phosphor, we need to follow a certain series of steps. We will go into more detail in another chapter, but here we only present a bare outline of the preparation of the phosphor- Mg2Sn04 Mn, where the actual formula is a solid solution of Mg2Sn04 Mn2Sn04 

As shown in the last chapter, luminescent-grade materials must have no more than a total of 100 ppm of impurities. The reaction that we will use to prepare our phosphor is  

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