Alumina encapsulated SrAl2O4:Eu2+, Dy3+ phosphors

Atomic layer deposition (ALD) of nanoscale coatings on SrAl2O4‐based phosphor powders to prevent aqueous degradation

“…These phosphors have excellent luminescence persistence in the blue/green region that can last for many hours . However, these aluminate‐based phosphors are susceptible to degradation in humid or aqueous environments, which restricts their usage in more sustainable waterborne coatings and/or external, zero‐energy lighting applications …”

“…Eu 2+ and RE 3+ dopants substitute for these Sr 2+ ions owing to similar radii: 1.26 Å for Sr 2+ versus 1.25 Å for Eu 2+ and 1.03 Å for Dy 3+ . Water molecules are believed to penetrate these channels, initially breaking the weaker Sr‐O bonds and eventually hydroxylating the AlO 4 tetrahedra, to decompose the structure …”

“…Both organic and inorganic coatings have been explored for preventing the decomposition of ceramic phosphors. To maintain good phosphorescence, these coatings must be optically transparent and homogeneous.…”

“…While organic coatings can provide good water stability, they limit high‐temperature postprocessing and/or operation. These coatings are also susceptible to degradation in organic solvents …”

Encapsulation of strontium aluminate phosphors to enhance water resistance and luminescence

“…A limited number of encapsulation methods are carried out to prevent hydrolysis of aluminate phosphors up to now. SiO 2 [14][15][16], Al 2 O 3 [17], TiO 2 [18], SrF 2 [19], BN [14] and organic ligands [20,21] are currently employed for encapsulation. In general, inorganic layers encapsulate phosphors by precipitation, while organic layers cover phosphors through coordination combination.…”