use of metal templates for microcavity formation in alumina

Figure 4.35 shows the phase equilibrium diagram of CuO- Al2O3 system. There
are several preliminary observations to be made on this diagram. At low temperatures,
no Cu2O is formed, only CuO, which does not react with Al2O3. At around 800°C,
Cu(AlO2)2= CuAl2O4 begins to be formed in this reported narrow 800-900°C. CuAlO2
is reported to be stable for all temperatures between 900°C and 1260°C, and also in
equilibrium with CuO or Al2O3 when unbalanced. At 1350 o C, copper has been almost
completely liquid phase.
Figure 4.35. Phase equilibrium diagram of CuO - Al2O3 system
(Source: Misra et al.,1963).
Figure 4.36 shows EDS analysis of the sample CR30F-Cu. According to EDS
results of the sample, Al and O are stable while we cannot see much Cu. Copper is
considered to be in liquid phase at 1350 o C. It is possible to melt out during heating and
only a minor fraction remained in alumina which was sufficient enough to impart some
color in the otherwise white alumina ceramic.
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