Preparation and luminescent properties of CaAl2O4:Eu3+,R+ (R=Li, Na, K) phosphors

CaAl2O4:Eu3+, R+ (R=Li+, Na+, K+) red phosphors were synthesized by solid state reaction method. X-ray diffraction (XRD) and photoluminescence (PL) were employed to characterize their structural and luminescent properties. It was found that the optimal sintering temperature and sintering time were 1200 °C and 4 h, respectively. The optimal concentration of doped Eu3+ was 3 mol.%. Furthermore, under ultraviolet excitation with a wavelength of 254 nm, these samples showed red luminescence which were probably attributed to the transitions from 5D0 excited state to 7FJ (J=0–4) ground states of Eu3+ ions. The feature and the high intensity of hypersensitive transition from 5D0→7F2 indicated that Eu3+ preferred to occupy a low symmetry site. The incorporation of alkali metal ions greatly enhanced the luminescence intensity probably due to the influence of charge compensation of alkali metal ions.