Doping level dependence of the structure and luminescence properties of LaBO3: Tb3+ phosphors

Tb3+ doped LaBO3 phosphors with various doping levels were synthesized by hydrothermal and post-calcination methods. The structure, morphology, chemical composition, and optical properties of the samples were studied by X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), Photoluminescence spectroscopy (PL). XRD patterns reveal that Tb3+ doped LaBO3 crystals with monoclinic or orthorhombic structures can be obtained by adjusting the doping content of Tb3+. The XPS and EDS results indicate that the elements of La, O, B, and Tb were uniformly distributed in the samples, and some doping Tb3+ were oxidized to Tb4+. The prepared Tb3+ doped LaBO3 phosphors emit green emission at 543 nm under 271 nm excitation. The luminescence intensity is affected by the Tb3+ doping level, and concentration quenching will be observed due to an electric quadrupole-electric quadrupole interaction (p-p) process when the Tb3+ doping amount rises above 22 %. In particular, the luminescence properties of the Tb3+ doped LaBO3 phosphors are dramatically affected by the structure of the samples, and the luminescence intensity of the samples with orthorhombic structure is significantly higher than those with monoclinic structure. The decay curves of samples exhibit a double exponential behavior, and the average luminescence lifetime decreases with an increase in Tb3+ doping levels.