- Strontium aluminate
Strontium aluminate (SRA, SrAl, StrontiumAluminum2Oxygen4) is a solid odorless nonflammable pale yellow powder, heavier than water. It is chemically and biologically inert. When activated with a suitable
dopant (eg.europium , then it is labeled SrAl2O4:Eu), it acts as a photoluminescentphosphor with long persistence ofphosphorescence . ItsCAS number is CASREF|CAS=12004-37-4.Strontium aluminate is vastly superior phosphor than its predecessor,
copper -activatedzinc sulfide ; it is about 10 times brighter, 10 times longer glowing, and 10 times more expensive than ZnS:Cu. It is frequently used inglow in the dark toys, where it displaces the cheaper but less efficient ZnS:Cu. However, the material has high hardness, causing abrasion to the machinery handling it; coating the particles with a suitablelubricant is usually used when strontium aluminate is added toplastic s.Strontium aluminate phosphors produce green and aqua hues, where green gives the highest brightness and aqua the longest glow time. The excitation wavelengths for strontium aluminate range from 200 to 450 nm. The wavelength for its green formulation is 520nm, its blue-green version emits at 505nm, and the blue one emits at 490nm. Colors with longer wavelengths can be obtained from the strontium aluminate as well, though for the price of some loss of brightness.
The wavelengths produced depend on the internal
crystal structure of the material. Slight modifications in the manufacturing process (the type of reducing atmosphere, small variations of stoichiometry of the reagents, addition ofcarbon orrare-earth halide s) can significantly influence the emission wavelengths.Strontium aluminate phosphor is fired at about 1250 °C. Subjecting it to temperatures above 1090 °C is likely to cause loss of its phosphorescent properties.
The glow intensity depends on the particle size; generally, the bigger the particles, the better the glow.
Strontium aluminate based afterglow pigments are marketed under brandnames like
Super-LumiNova [ [http://www.rctritec.com/index.php?id=13 RC TRITEC Super-LumiNova] ] [ [http://www.nemoto.co.jp/en/products/luminova/index.html Nemoto & Co., Ltd LumiNova] ] or NoctiLumina [ [http://www.noctilumina.com/ NoctiLumina company website] ] .References
External links
* [http://science.howstuffworks.com/question388.htm How does glow-in-the-dark stuff work?]
* [http://www.theodoregray.com/periodicTable/Elements/038/index.html Facts, pictures, stories about the element Strontium]
* [http://www.hf.faa.gov/docs/508/docs/cami/9802.pdf Performance Demonstrations of Zinc Sulfide and Strontium Aluminate Photoluminescent Floor Proximity Escape Path Marking Systems]
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