Photoluminescent properties of europium doped calcium orthogermanate (Ca2GeO4) as a candidate for Red phosphor

Abstract

Powder samples of Ca2GeO4 doped with 0.5, 1, 2, 3, 4 and 5 at% Eu3+ were prepared by conventional solid state synthesis technique. XRD analyses confirm obtaining of the pure phase at all dopant concentrations. Emission and excitation spectra show the characteristic peaks of Eu3+ ion. The strongest peak in excitation spectra in the range from 300 to 500 nm is located at 393 nm corresponding to the 7F0→5L6 transition. The luminescent spectra consist of the characteristic peaks of Eu3+ ion. The 5D0→7F2, 4 electric dipole transitions are dominant, confirming that the presence of Eu3+ ion in position without inversion symmetry in the host is preferable. The peaks are split, so the dopant is placed in more than one crystallographic position. CIE coordinates of the samples show emission colors in the red region slightly influenced by the active ion concentration. The sample doped by 1 at% Eu3+ show chromaticity coordinates close to the standard red chromaticity coordinates (0.6270, 0.3726). The obtained results confirm that europium doped Ca2GeO4 by could be used as a red phosphor.