Energy storage phosphors

Energy storage phosphors are materials in which an irradiation induces ionization of some ions followed by capture of the extracted electrons by vacancies, forming colour centres, or oxidizing cations. By irradiation in the absorption bands of the centres so created (photostimulation) or temperature rise, the trapped electrons can be released and the recombination energy with holes transferred to a luminescent ion. 

Iitg. 8,4. Energy band model showing the electronic transitions in a storage phosphor (a) generation of electrons and holes (b) electron and hole trapping (c) electron release due to stimulation (4) recombination. Solid circles are electrons, open circles are holes. Center I presents an electron trap, center 2 a hole trap... 

The stoted energy can be released by thermal or optical stimulation. In the case of thermal stimulation the irradiated phosphor is heated to a temperature at which the energy barrier AE can be overcome thermally. The trapped electron (or hole) can escape irom the trap and recombine with the trapped hole (or electron). In the case of radiative recombination, luminescence is observed which is called thermally stimulated luminescence (TSL) (compare Sect. 3.5). Under optical stimulation the energy of an incident photon is used to overcome AE. The luminescence due to optical stimulation is called photostimulated lumine.scence (PSL). The phenomenon of stimulated luminescence from storage phosphors has been known since 1663 (Boyle). Storage phosphors have found a wide range of applications, e.g. as infrared detectors and in the field of dosimetry [3J. 

Kallmann H, Sucov E Energy storage in ZnS and ZnCdS phosphors. Physical Reviews 1958, 109(5) 1473-1478. 

Compounds of one acid with another are referred to as acid anhydrides. A particularly large amount of energy is required for the formation of an acid—anhydride bond. Phosphoric anhydride bonds therefore play a central role in the storage and release of chemical energy in the cell (see p. 122). Mixed anhydrides between carboxylic acids and phosphoric acid are also very important energy-rich metabolites in cellular metabolism. 

Acid Fuel Cells Phosphoric Acid Electrolyte - Fickett, A.P., Fuel Cell Electrolysis Where Have We Failed Proc. of the Symp. on Electrode Materials and Processes for Energy Conversion and Storage, J.D.E. McIntyre, S. Srinivasan and F. G. Will (Eds.), Vol. 77-6, 546-558. Electrochemical Society, Princeton, Mew Jersey, 1977. 

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