Luminescence of (H3O)Al3(SO4)2(OH)6:Cu synthesized under hydrothermal condition

Copper doped hydronium alunite; (H3O)Al3(SO4)2(OH)6:Cu was successfully synthesized under hydrothermal conditions. The blue cathodoluminescence (peak at about 414 nm) was observed from the (H3O)Al3(SO4)2(OH)6:Cu when the copper ratio x was 1 and above, where x was the molar ratio of Cu:Al:S = x:3:2 (0 ≤ x ≤ 15) in the starting materials. The luminescence intensity increased with increasing x up to 3, and then decreased. The monovalent copper ion (Cu+) was detected by XPS measurements for all the doped samples. In addition, the divalent copper (Cu2+) was detected for the samples with x ≥ 6. Therefore, the origin of the blue luminescence is considered to be monovalent Cu+ ion. Excess doping of Cu+ (x ≥ 6) is thought to cause a concentration quenching of the luminescence. The obtained (H3O)Al3(SO4)2(OH)6:Cu is expected to find use in the blue luminescent phosphor under electron beam irradiation.