Materials Science of the Luminescence of Inorganic Solids
The dependence of emission and excitation spectra of luminescent centres on the nature of the host lattice is discussed and exemplified by the following cases: Eu3+, Eu2+, NbO 6 7- and Pr3+. The quantum efficiency of isolated luminescent centres is reviewed from the point of view of a general approximation and from the point of view of some specific examples (trivalent rare-earth ions; including the effects of charge-transfer and 4fn-15d states). Concentration quenching of luminescence is dealt with starting from a discussion of energy transfer. The concept of energy migration through a host lattice is outlined. Concentration quenching by cross-relaxation in rare-earth ions closes this section. Sensitized luminescence is discussed as a consequence of energy transfer between unlike, luminescent centres. From the foregoing, rules are derived to predict the composition of efficient phosphors. This is illustrated for two special cases in the application field, viz. the Eu3+ ion (red colour television phosphor) and the rare-earth activated phosphors applied in a new generation of fluorescent lamps.
KeywordsEnergy Transfer Host Lattice Luminescent Centre Concentration Quenching Nonradiative Transition
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