Intense violet-blue-emitting Ba ₂ AlB ₄ O ₉ Cl:Eu ²⁺ phosphors for applications in fluorescent lamps and ultraviolet-light-emitting diodes

We synthesized a violet-blue phosphor Ba ₂ AlB ₄ O ₉ Cl:Eu ²⁺ with a solid-state reaction. The excitation and emission spectra of this phosphor showed that all were broadband due to 4f ⁷ - 4f ⁶ d ¹ transitions of Eu ²⁺ . The phosphors with different Eu ²⁺ concentrations presented violet-blue luminescence for ultraviolet [(UV) 250-390 nm] excitation. The optimum concentration of Eu ²⁺ in Ba ₂ AlB ₄ O ₉ Cl:Eu ²⁺ is determined to be 6 mol:%. The luminous efficiency was found to be 8:1 lm/Wfor the violet-blue fluorescent lamp and 3:2 lm/W for the violet-blue phosphor-converted light-emitting diode, respectively. Ba ₂ AlB ₄ O ₉ Cl:Eu ²⁺ would be a promising phosphor for converting the UV radiation to violet-blue emission for a novel high light-conversion efficiency phototherapy illuminator.