Effect of Host Structure

Little has been said concerning this parameter because of its complexity. The subject is so complicated that a separate treatise could be written on this subject alone. Essentially, it involves two factors 1) the site symmetry at the cation site, and 2) the strength of the crystal field at that site. Consider the activator, Sn2+. As we change the host, the emission colors 

The emitting state for Sn2-i- is the state. The free-lon energy level lies above 40,000 cm i. But in a crystal field, this level splits into three field components. For this reason, we can vary the emission band of Sn2+ by varying the nature of the host employed. 

Crystal Structure Lattice symmetry Cation Site 

19- IN THE SELECTION OF HOST COMPOUNDS TO PREPARE A PHOSPHOR, WE AVOID THOSE WHICH POSSESS A LOW TEMPERATURE FORM, ESPECIALLY IF THEY HAVE A LOW TRANSITION TEMPERATURE. 

This explains the non-lumlnescent behavior of the Mg2P207 forms. 

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