A Strontium Aluminosilicate SrAl ₂ SiO ₆ Offering a Scalable Route to Persistent Luminescent Materials

The substitution of silicon into SrAl 2 O 4 is of interest for the development of new persistent luminescence phosphors with complementary excitation and emission wavelengths, especially in the form of transparent ceramics or glass-ceramics by the glass-crystallization approach. Application of this approach to the series Sr 1– x /2 Al 2– x Si x O 4 (0 ≤ x ≤ 1) has previously produced two different solid solutions adopting either the three-dimensional stuffed tridymite structure of SrAl 2 O 4 (0 ≤ x ≤ 0.5), or the two-dimensional hexacelsian structure of SrAl 2 Si 2 O 8 (0.8 ≤ x ≤ 1.0), with a compositional gap between 0.5 < x < 0.8. Here, we synthesize a solid solution centered around SrAl 2 SiO 6 ( x = 0.66), which is accessible in the range 0.60 ≤ x ≤ 0.75 by glass crystallization. The crystal structure of SrAl 2 SiO 6 features an aluminosilicate framework that is related topologically to SrAl 2 O 4 (stuffed tridymite) and also, more distantly, to SrAl 2 Si 2 O 8 (hexacelsian), representing a stepwise reduction in framework dimensionality across the series. SrAl 2 SiO 6 exhibits an unusual pale blue-green persistent luminescence when doped with Eu 2+ /Dy 3+, and can be produced as powders or transparent glass-ceramic disks. The pale afterglow color, transparency and scalability of these materials are complementary to the dominantly green persistent luminescence of SrAl 2 O 4 -based powders or single crystals.