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Defect related spectroscopic properties of Yb-doped CaF2 nanocrystals
The CaF₂ nanocrystals doped with different concentrations of Yb-ions were obtained and carefully characterised. The X-ray diffraction measurements confirmed the cubic structure of the fluorite, although slight lattice distortions were observed at higher doping levels. The transmission electron microscopy images revealed well dispersed nanoparticles with an average size of 10 nm. The high-resolution images have enabled the direct visualisation of the distribution of Yb3+-clusters located at Ca2+ sites within these nanocrystals, as well as their statistical analysis. Based on the vibrational spectroscopy structural distortions were confirmed to occur upon doping. The spectra exhibited Yb³⁺ ion luminescence characteristic of typical infrared emission in the 2F7/2→2F5/2 transition region, as well as characteristic anti-Stokes emission in the visible region. Additional measurements with deep ultraviolet were performed to analyse defect related emission in the nanocrystals. Thermoluminescence curves and electron paramagnetic resonance spectra have been carried out to investigate the existence of defects that could be used as trapping centres in the persistent luminescence process.
Dr. Dariusz Hreniak is a professor at the Institute of Low Temperature and Structure Research of the Polish Academy of Sciences in Wroclaw, Poland. Graduated from the Wroclaw University of Science and Technology with a master's degree in materials engineering in 2000, obtained a doctor degree in chemical sciences in 2005 at the Institute of Low Temperature and Structure Research, followed by a post-doctoral degree of habilitated doctor in Chemical Sciences in 2011 and the title of full professor in chemical sciences in 2022. Fields of interest are related to the study of optical materials, in particular luminescent materials, and the characterization of luminescent properties of lanthanide ions in glasses, ceramics and nanocomposites. Current interests mainly concern size effects in persistent phosphors. Member of the Editorial Board of the journals Optical Materials (since 2005) and Optical Materials X (since 2021). Scientific secretary of 9 international conferences. Chair and co-chair of scientific committees of 4 international conferences. Member of the board in CTT INtech Sp. z o.o. (since 2014) company belongs fully to the ILT&SR PAS and being a commercialization support and the technology transfer office. Co-author of 30 national and international patents and patent applications resulting from R&D projects. Published papers in total: 235. Number of citations (27/08/2026): 4,751 (without self-citations), H-index = 38 (Web of ScienceTM).
