  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.
