Morphology and Photoluminescence Properties of the GdPO₄:Ce, Tb Nanomaterials with Ultrasonic-assisted Synthesis Characterized by X-ray Diffraction, Infrared Spectroscopy and Scanning Electron Microscopy

Ultrasonic assisted method is an effective method to prepare nanomaterials, which can improve their magnetic and optical properties. Described in this paper, GdPO₄:Ce, Tb ternary system fluorescent powder was synthesized under different pH conditions by ultrasonic-assisted. Optical and structural properties of the fluorescent powder were determined by X-ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Photoluminesce (PL).The following conclusions are drawn:(1) When pH=1, synthetic samples are 15 nm×104 nm hexagonalnanobars like orthophosphate, green phosphor. Cystals prefer growing at the face of (102) and (200). When pH < 1, no samples can be synthesized, whereas granular orthophosphate green phosphors were synthesized when pH>1. (2) A possible formation mechanism has been put forward, which provided further evidence for the fluorescent efficiency enhancement. Because the 5d energy states of Ce³⁺ ions are high, they can be transferred to the Gd³⁺ ions efficiently. However, the emission transition peak of Gd³⁺ ions and the absorption peak of Tb³⁺ ions have large spectral overlap in the Gd, Ce, Tb ternary system. Therefore, the sequence of energy transmission is the Ce³⁺→Gd³⁺→Tb³⁺. A few Ce³⁺ ions doping to GdPO₄ matrix can enhance fluorescence intensity of the luminescent materials. The result provides theoretical basis for the exploit of rare earth materials.