Cathodo- and photoluminescence of (H3O)Al3(SO4)2(OH)6:Cu synthesized under hydrothermal conditions

Copper-doped hydronium alunite ((H3O)Al3(SO4)2(OH)6:Cu) was synthesized under hydrothermal conditions (240 deg. C, 60 min) from copper nitrate and aluminium nitrate solutions mixed with elemental sulfur. SEM and XRD measurements revealed that pseudocubic crystals of hydronium alunite and a small amount of boehmite rods coexisted in the resultant product. XPS measurements revealed the presence of monovalent copper (Cu+). Blue cathodoluminescence and photoluminescence were observed at about 414 and 419 nm, respectively. Two photoluminescence excitation bands were found at 295 and 325 nm. The excitation and emission processes for photoluminescence may involve the 3d10↔3d94s1 transition of the Cu+ ion. (H3O)Al3(SO4)2(OH)6:Cu has the potential to be used as a blue luminescent phosphor for both electron beam and ultraviolet irradiation.