Preparation and luminescence properties of KLaSiO4:Tb3+ phosphors

KLaSiO₄:Tb³⁺ phosphors were synthesized using the sol–gel method. The structure and luminescence properties of the materials were characterized using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry–differential thermal analysis, fluorescence spectra and calculated Commission Internationale de l'éclairage coordinates. The results showed that the material had a hexagonal structure, and that doping of Tb³⁺ did not change the crystal structure of KLaSiO₄. FTIR spectroscopy confirmed the existence of stretching vibrations of Si–O, bending vibrations of Si–O–Si, and asymmetric tensile vibrations of Si–O in KLaSiO₄. The excitation spectrum of the sample consisted of 4f⁷→5d¹ broadband absorption and the characteristic excitation peak of Tb³⁺, the excitation peak at 232 nm belongs to the spin allowed ⁷F_J→⁷D_J transition of Tb³⁺, the excitation peak at 268 nm belongs to the spin forbidden ⁷F_J→⁹D_J transition of Tb³⁺, and the absorption band of ⁷F_J→⁷D_J transition is split. Under excitation at 232 nm, the emission peak of the sample was composed of the ⁵D₄→⁷F_J (J = 6, 5, 4, 3) energy level transition of Tb³⁺. The highest emission peak is located at 543 nm, which belongs to the ⁵D₄→⁷F₅ transition and emits green light. Concentration quenching occurred when the Tb³⁺ doping concentration was greater than 1% mol, the quenching mechanism was an electric dipole–electric dipole action. When the ratio of citric acid to total metal ions was 1:1 and the annealing temperature was 800°C, the surface defects of the phosphors were greatly reduced, the quenching effect was reduced, and the luminous intensity reached the maximum.