The Effects of Purity And Impurities

Our study has led us to the point where we can realize that the primary effect of impurities in a solid is the formation of defects, particularly the Frenkel and Schottky types of associated defects. Thus, the primary effect obtained in purifying a solid is the minimization of defects. Impurities, particularly those of differing valences than those of the lattice, cause charged vacancies and/or interstitials. We can also increase the reactivity of a solid to a certain extent by making it more of a defect crystal by the addition of selected impurities. 

The GRADES listed above are named for the usage to which they are intended, and are usually minimum purities required for the particular application. Fiber-optic materials are currently prepared by chemical vapor deposition techniques because any handling of materials introduces impurities. Furthermore, this is the only way found to date to prepare the required materials at this level of purity. 

The frontiers of purity achievement of solids presently lie at the fraction of pcirts per billion level. However, because of Environmental Demands, analytical methodolo presently available far exceeds this. We can now analyze metals and anions at the femto level (parts per quadrillion= 10 15 ) if we wish to do so. 

Nevertheless, it is becoming apparent that as high puiily inorganic solids are being obtained, we observe that their physical properties nu be 

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