Dialuminum strontium oxygen(2-)
|Molar mass||205.58 g/mol|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Strontium aluminate (SRA, SrAl, SrAl2O4) is a solid odorless, nonflammable, pale yellow powder, heavier than water. It is chemically and biologically inert. When activated with a suitable dopant (e.g. europium, then it is labeled SrAl2O4:Eu), it acts as a photoluminescent phosphor with long persistence of phosphorescence.
For many phosphorescent-based purposes, strontium aluminate is a vastly superior phosphor to its predecessor, copper-activated zinc sulfide; it is about 10 times brighter and 10 times longer glowing, however it is about 10 times more expensive than ZnS:Cu and it cannot produce the unique red phosphorescence of the latter. It is frequently used in glow 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; manufacturers frequently coat the particles with a suitable lubricant when adding them to a plastic.
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 520 nm, its blue-green version emits at 505 nm, and the blue one emits at 490 nm. 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 of carbon or rare-earth halides) 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 doped with Europium and Dysprosium is called Lumibrite developed by Seiko and claimed to be brighter and longer glow time compare to ordinary Strontium aluminate doped with only Europium.
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