Preparation and luminescent properties of Ca2Si(O4-xNx)：Eu2+ green-emitting phosphors

A nitrogen-contained solid solution Ca2Si(O4-xNx):Eu2+ green phosphors was successfully synthesized using the method of mixing Ca-Si-O xerogel precursor with Si3N4 powders in a non-reducing atmosphere (pure nitrogen). The structure, morphology, and luminescent properties of the phosphors are characterized by X-ray diffraction (XRD), \text {scanning} electron microscopy (SEM) and photoluminescence (PL) spectra. Results show that the Ca2Si(O4-xNx):Eu2+ is obtained and especially the reduction of Eu3+ to Eu2+ occurs when the mixture of Si3N4 and precursor is calcined at 1100℃ in pure nitrogen atmosphere. XRD results show that the crystalline structure of N-contained solid solution Ca2Si(O4-xNx):Eu2+ is consistent with that of βup -Ca2SiO4 phase. The phosphors can be efficiently excited at a wavelength of 270–400 nm and shows a single intense broadband emission (450–600 nm). Significantly, the red-shift (501 nm to 504 nm) of emission peak occurs and the luminescent intensity is improved significantly with increasing N concentration. With increasing Eu2+ concentration, luminescent intensity of the phosphors increases continuously and reaches a maximum value at the concentration of 0.25 mol% Eu2+. Then the luminescent intensity decreases significantly and the concentration quenching effect appears when Eu2+ concentration is above 0.25 mol%.