Near-Infrared Emitting Nd³⁺:LaF₃ Nano-Glass-Ceramics Produced by Sol-Gel Technology

In this work, the series of sol-gel materials doped with Nd³⁺ ions were synthesized and further transformed into nano-glass-ceramics containing LaF₃:Nd³⁺ nanocrystals via controlled heat treatment, carried out at 700°C and 900°C. The structural characterization of materials obtained at different temperature conditions was performed using x-ray diffraction analysis (XRD), revealing a crystallization of the fluoride nanophase. The examination of luminescent properties included analysis of PLE and PL spectra recorded using different excitation wavelengths. The characteristic emission bands of Nd³⁺ ions within near-infrared (NIR) spectral scope were observed for all fabricated samples. Furthermore, the luminescence decay curves of the ⁴F_3/2 state of Nd³⁺ were registered. It has been demonstrated that samples annealed at a higher temperature level (900°C) exhibited more intense NIR luminescence bands and longer lifetimes of the ⁴F_3/2 excited state, compared with the series fabricated at 700°C. Indeed, the luminescence lifetimes noted for materials annealed at 700°C ranged from 141 to 772 μs, whereas those obtained for materials heat-treated at 900°C ranged from 213 to 862 μs. Based on the obtained results, it was concluded that the Nd³⁺ ions were partially incorporated into LaF₃ nanocrystals, thus the fabricated sol-gel materials are promising candidates for the NIR luminescence applications.