Preparation and optical properties of Bi³⁺-doped K₄SrGe₃O₉ as a UVA phosphor

Optical materials with UV emission have diverse applications, for example, in phototherapy, anti-counterfeiting, disinfection, and photocopying. Yet, these materials are mainly activated by rare earth ions with narrow and inflexible emission characteristics. Here, we report on UVA emission from a Bi 3+ -doped K 4 SrGe 3 O 9 phosphor synthesized by conventional high-temperature solid state reaction at ambient atmosphere. The structure, morphology and luminescent properties of the material were characterized using X-ray diffraction, scanning electron microscopy (SEM) and photoluminescence spectroscopy, demonstrating broadband emission of ultraviolet-A (UVA) light peaking at 353 nm (FWHM ∼ 46 nm) when stimulated by ultraviolet radiation at a wavelength of 304 nm. The maximum emission intensity was found for K 4 SrGe 3 O 9 :0.001Bi 3+ , with a quantum yield of 46% and a lifetime of 477 ns.