Preparation of the NaTaO₃ Crystal from the KTaO₃ Substrate via Topotactic Alkaline Cation Substitution as Confirmed by Transmission Electron Microscopy

Abstract

Orthorhombic-type sodium tantalite (NaTaO₃) is one of the most promising photocatalyst for hydrogen generation via water splitting reaction with ultraviolet-irradiation. In this research, we prepared NaTaO₃ crystal from KTaO₃ substrate via solid-state K⁺−Na⁺ alkaline cation substitution. In the transmission electron microscopy (TEM) observation revealed the perovskite-type KTaO₃ crystal phase is transformed into the orthorhombic crystal phase via simple heating of KTaO₃ substrate with Na₂O₂. Atomic scale scanning TEM imaging with energy dispersive X-ray spectroscopy (EDS) are supported that this phase transformation clearly based on the topotactic alkaline cation substitution with K⁺ and Na⁺ at a common Ta-O basic lattice structure.