Insights into NiTeO calcination synchrotron X-ray diffraction.

The versatility of metal tellurate chemistry enables the creation of unique structures with tailored properties, opening avenues for advancements in a wide range of applications. However, precise nanoengineering of NiTeO, a ceramic Ni tellurate with a broad variety of properties, like electrical, magnetic, photocatalytic and multiferroic properties, demands a deep understanding of the synthesis process, which is strongly influenced by experimental parameters. This study delves into the formation mechanism of NiTeO nanoparticles during calcination of hydrothermally produced precursors, using synchrotron X-ray diffraction, complemented by post-mortem TEM and XPS, and thermal analysis. The results reveal a reaction sequence involving dehydration and dehydroxylation of stoichiometric Ni/Te oxyhydroxide coordinated by Te. This oxyhydroxide can be schematically represented by a formula of (3Ni/Te)(OOH)·HO. Subsequently, preferential nucleation of NiTeO occurs. Further calcination after full crystallization of NiTeO leads to the formation of a different Ni tellurate (NiTeO) phase as an impurity. These findings clarify the reactions occurring during calcination of Ni/Te mixed precursors, which have frequently been inferred from empirical and post-mortem reports but not confirmed comprehensive and guided explorations.