Crystalline Inorganic Phosphors

The luminescence of inorganic phosphors is comprised of the following processes 1) absorption and excitation, 2) energy transfer, and 3) emission. 

Excitation requires that energy acts on the phosphor that can be absorbed by it. The excitation mechanism differs according to the type of energy involved. 

Excitation by Photons. The dependence of the absorptivity of a phosphor upon the photon energy is given by the absorption spectrum. This can be divided into various regions such as basic lattice absorption, edge absorption, and defect absorption [5.307]. 

excitation only takes place with photons of higher energy. The absorption that is effective for excitation of luminescence is given by the excitation spectrum, which shows the dependence of the luminescence intensity on the photon energy. Strong luminescence occurs when the exciting photon has sufficient energy to promote an electron from the valence band to the conduction band. 

Energy Configuration Diagram. This model, based on the energy level diagrams of atoms and molecules, is applicable to luminescence processes in which excitation and emission take place at the same luminescence center. 

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Most crystals will emit light when fractured. Because most inorganic phosphors have a crystalline structure, they should emit TL. One phosphor, namely, zinc sulfide doped with manganese (ZnS Mn), has often been noted for its TL. To develop an effective phosphor-based sensor, the relationship between TL intensity and impact velocity for ZnS Mn or any other material must be quantified. 

A series of aluminum phosphite and phosphite-phosphate molecular sieves were synthesized by using P (III) (phosphorous acid) partly or completely replaced P (V) (phosphoric acid) as the source of phosphorus materials. DPA (di-n-propylamine), TEA (triethylamine) and CHA (cyclohexylamine) were used as the template respectively. SEM photographs showed the shapes of these crystalline inorganic solid. It was very interesting that a kind of aluminum phosphite NKX-4 can be synthesized with or without template. 

The luminescent material may be considered as a transformer of energy, i.e.. from ultraviolet photons to photons of lower energy from cathode rays to photons front electric fields to photons, etc. An inorganic luminescent material, or phosphor, usually consists of a crystalline host materia) to which is added a trace of an impurity (activator and eoactivaturl. 

A large number of inorganic layer crystals such as micas, sodium silicates, niobate, uranate, vanadate, titanate, zirconium phosphate, graphitic acids, crystalline silicic acids, vanadium oxyhydrate, calcium phosphoric acid esters, and titanium disulfide develop alkyl crystals between their rigid crystal layers by ion exchange with, for example, alkyl ammonium salts and by intercalation inorganic... 

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