Effect of Gd-codoping on photoluminescence properties of Eu-doped natural fluorapatite

Abstract

This study investigated the photoluminescence properties of Eu, Gd, and Eu-Gd co-doped natural fluorapatite (FAP) particles. Ca10(PO4)6F2:EuxGd0.2−x powders were synthesized by the solid-state powder synthesis method at 1150 ⁰C. X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-Ray Spectroscopy, and Photoluminescence Spectroscopy (PL) were used to characterize the structural, morphological, chemical, and optical properties, respectively. XRD and FTIR analysis demonstrated the presence of mainly FAP while CaO and larnite as minor phases. Approximately 1–2 µm equiaxed FAP particles were seen in SEM microstructure images. Regardless of Gd3+, in the presence of Eu3+, under 253 nm excitation, the FAP samples showed characteristic emission bands of Eu3+ at 600 nm and 625 nm originating from 5D0→7F1 and 5D0→7F2 transitions, respectively. In addition, a noticeable increase was observed in the emission intensity of Eu3+ with the addition of Gd3+. On the other hand, the Gd-doped FAP sample showed an emission band at 320 nm originating from the Gd3+ 6P7/2→8S7/2 transition under excitation at 205 nm. As a result, the emissions of Eu-FAPs were improved with the Gd-codoping, and materials with high color purity and excellent chromaticity coordinate characteristics were obtained.