Synthesis, crystal structure and investigation of ion-exchange possibility for sodium tellurate NaTeO3(OH)

Abstract

A new sodium tellurate has been hydrothermally synthesized and comprehensively analysed using spectroscopic and thermogravimetric techniques, resulting in the determination of its composition as NaTeO₃(OH). The analysis of synchrotron X-ray and neutron diffraction data indicates that NaTeO₃(OH) has a crystal structure similar to that of the previously reported tellurate, KTeO₃(OH), with the space group P2₁/a (No. 14). NaTeO₃(OH) consists of zigzag one-dimensional chains built by edge-sharing TeO₆ octahedra, running parallel to the c-axis and connected to sodium and hydrogen atoms. The hydrogen atoms covalently bond to the terminal oxygen atoms on the one-dimensional chain and also form hydrogen bonds with other terminal oxygen atoms on nearby chains. The structure has been confirmed by optimization using the pseudopotential method and performing Bond Valence Sum (BVS) analysis. Although Li⁺ ions in LiTeO₃(OH) can be exchanged reversibly with H⁺ ions, no ion exchange behaviour is observed in NaTeO₃(OH). The difference is attributed to the size of the alkali ions and their crystal structure.