Strontium aluminate
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IUPAC name
Dialuminum strontium oxygen(2-)
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3D model (Jmol)
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| ECHA InfoCard | 100.031.310 |
| EC Number | 234-455-3 |
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PubChem CID
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| Properties | |
| SrAl2O4 | |
| Molar mass | 205.58 g/mol |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Strontium aluminate (SRA, SrAl, SrAl2O4) is a solid odorless, nonflammable, pale yellow, monoclinic crystalline 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.
There are also other strontium aluminates, e.g. SrAl4O7 (monoclinic), Sr3Al2O6 (cubic), SrAl12O19 (hexagonal), Sr4Al14O25 (orthorhombic).
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.
Different aluminates can be used as the host matrix. This influences the wavelength of emission of the europium ion, by its covalent interaction with surrounding oxygens, and crystal field splitting of the 5d orbital energy levels.
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.
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