Unconventional and Powerful Ion Sources for Solid-State Ion Exchange, Cu2SO4 and Cu3PO4: Exemplified by Synthesis of Metastable \beta-CuGaO2 from Stable \beta-LiGaO2

TL;DR

This paper presents a novel approach for synthesizing metastable Cu+-containing phases using powerful ion sources identified through first-principles calculations, enabling new reaction pathways in solid-state ion exchange.

Contribution

It introduces Cu2SO4 and Cu3PO4 as effective ion sources for solid-state ion exchange, expanding the synthesis of metastable materials beyond traditional methods.

Findings

Cu2SO4 and Cu3PO4 provide higher thermodynamic driving force than CuCl.

Successful synthesis of metastable eta-CuGaO2 from eta-LiGaO2.

First-principles calculations effectively guided the selection of ion sources.

Abstract

This study introduces a new method for synthesizing Cu+-containing metastable phases through ion exchange. Traditionally, CuCl has been used as a Cu+ ion source for solid-state ion exchanges; however, its thermodynamic driving force is often insufficient for complete ion exchange with Li+-containing precursors. First-principles calculations have identified Cu2SO4 and Cu3PO4 as more powerful alternatives, providing a higher driving force than CuCl. It has been experimentally demon-strated that these ion sources can open up new reaction pathways through experimental ion exchanges, such as from \beta-LiGaO2 to \beta-CuGaO2, which were previously unattainable. An important perspective provided by this study is that the poten-tial of such basic compounds to act as powerful ion sources has been overlooked, and that they were identified through straightforward first-principles calculations. This work presents the initial strategic design of an ion exchange reaction by exploring suitable ion sources, thereby expanding the potential for synthesizing metastable materials.