Orange-red luminescence features of Eu3+doped CaAl4O7 phosphors

A series of orange-red emitting Eu3+ doped CaAl4O7 phosphors was synthesized by the citric acid sol gel process using the metal nitrates as precursors. A study of the phosphors according to their X-ray diffraction patterns confirmed the desired phase without any intermediate or precursor compounds. The SEM imaging does not reveal the crystal structure, but it shows a variation of crystalline size within a few micrometers. In the excitation spectrum of CaAl4O7:xEu3+ (x = 0.01-0.11 mol), sharp multiple peaks at 293 nm, 464 nm, and 533 nm which are charac-teristics of Eu3+ transitions from 7F-* 5D were observed. The photoluminescence emission spectra with an excitation wavelength of 464 nm showed characteristic peaks corresponding to the transition of 5D0-* 7F2 at 612 nm and expressed orange-red region of the electromagnetic field. The emission intensity increased as the concentration of Eu3+ increased to 0.05 mol, where it exhibited the highest emission intensity in the series. The intensity ratio results also indicate an intensity drop after a 0.05 concentration of the Eu3+ ion. The full width at half maximum (FWHM) of the synthesized phosphors is expressed as the concentration increase, which leads to a drop in sharpness. The chromaticity properties indicate high color purity of the synthesized phosphor in the orange-red region by the position of the color coordinates at the edge of the CIE color chromaticity diagram.