Narrowband ultraviolet B emitting Gd doped CaAl2O4 phosphors - An ESR and photoluminescence study

Phosphors with the composition Ca1-xGdxAl2O4 (x = 0.0025-0.09) were synthesized by a simple combustion route in a short time. The formation of the as-prepared combustion products was confirmed by the X-ray diffraction analysis, indicating the formation of a monoclinic phase. The PL spectroscopy assessment shows that with increasing Gd3+ concentration, the ultraviolet emission from Gd3+ at 314 nm (6P7/2→8S7/2) progressively enhanced. The Gd3+-doped CaAl2O4 displays electron spin resonance signals with the effective g values at g ≈ 1.95, 2.9, and 3.7. Additional lines were also observed at the approximate g values of ~2.2 and 5.3. Gd3+ ion located in the distorted surroundings and experiencing relatively strong crystal field, give rise to low field lines. Distorted surroundings in the present system may result from the nearness of the charge compensator oxygen vacancies.