JultikaUniversity of Oulu repository

Abstract

For this thesis, X-ray photoelectron spectroscopy (XPS) was used to study copper tellurates synthesized at different pH values using novel hydrothermal synthesis. Copper tellurate compound (Cu3TeO6) is a semiconductor that belongs to the metal tellurate family and exhibits fascinating electronic and magnetic properties like antiferromagnetism. It also has applications in ceramics and as a possible drug sensor. The new hydrothermal synthesis route provides better control over the composition and size of the nanoparticles. Since there is high interest in these materials and a new synthesis method has been used, a thorough characterization is needed.

XPS is a surface-sensitive method based on the photoelectric effect and is suitable for identifying elements and chemical states in the sample. Here, XPS spectra were peak fitted to identify the binding energies of copper, tellurium, and oxygen species in the samples. Copper was revealed to be Cu(II) species, tellurium spectra included both Te(IV) and Te(VI) components, meanwhile, oxygen spectra had a strong shoulder peak for either hydroxide or defective oxygen, the latter of which would explain the unexpected Te(IV) peak. The results also showed the presence of a hydroxide component, which was removed by calcination. Chemical shifts were observed for copper and tellurium peaks. The findings of this study provide insights into the synthesis and properties of copper tellurates, which can guide future research.