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Description
The geopolymer obtained by the standard procedure of alkaline activation of metakaolin is doped with samarium (Sm) and neodymium (Nd) ions. The mass concentration of the dopant in both cases is 5%. After doping, the obtained materials were thermally treated at 600°C in a tube furnace in a stream of argon for 1 hour [1]. After cooling, the obtained materials were characterized using: Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Fourier Transrorm Infrared Spectroscopy (FTIR) and Spectroscopic Ellipsometry (SE). SEM analysis revealed that thermal exposure induces dehydroxylation, crystallization, and sintering processes, which are reflected in both morphological (SEM) and chemical (EDS) changes. The SEM micrographs also present a low degree of geopolymerization, as evidenced by the presence of numerous unreacted particles, indicating limited dissolution of the precursor material. HR-TEM clearly shows the differences between the crystal planes in the geopolymer, the presence of Al and Si phases as well as the polycrystalline structure of the doped geopolymer even after thermal treatment [2]. FTIR spectroscopy was performed to examine the structural evolution, and confirmed existence of hydroxyl groups bonded within the gel in the range of about 3450 cm-1 was. Spectroscopic ellipsometry (SE) showed absorption of Nd and Sm dopants in the UV region in the range from 290 nm to 373 nm. It is indicative that both dopants representing rare earths show activity in the UV region.