Thermodynamic investigations on the growth of CuAlO$_2$ delafossite crystals

TL;DR

This study investigates the thermodynamic conditions for growing CuAlO$_2$ delafossite crystals, identifying suitable crucibles and phase diagram parameters to optimize crystal growth in oxidizing atmospheres.

Contribution

It provides new thermodynamic data and phase diagrams crucial for the controlled growth of CuAlO$_2$ delafossite single crystals.

Findings

Sapphire and platinum crucibles are stable for crystal growth.

Crystals can be grown from copper oxide melts with 1-2 mol % aluminum oxide.

Stable growth occurs in oxidizing atmospheres with 15-21% oxygen.

Abstract

Simultaneous differential thermal analysis (DTA) and thermogravimetric (TG) measurements with copper oxide/aluminum oxide mixtures were performed in atmospheres with varying oxygen partial pressures and with crucibles made of different materials. Only sapphire and platinum crucibles proved to be stable under conditions that are useful for the growth of CuAlO$_2$ delafossite single crystals. Then the ternary phase diagram Al$_2$O$_3$-CuO-Cu and its isopleth section Cu$_2$O-Al$_2$O$_3$ were redetermined. Millimeter sized crystals could be obtained from copper oxide melts with 1-2 mol % addition of aluminum oxide that are stable in platinum crucibles held in oxidizing atmosphere containing 15-21 % oxygen.