Fig. 3 shows SEM images of surface microstructures for
the ceramics sintered at different sintering times. As can
be seen from Fig. 3(a)‐(c), the microstructures of
CaCu2.9Zn0.1Ti4O12 change significantly with sintering
time. In specimen sintered at 950 ºC for 6h a porous with
small grain size 8‐10 μm is observed. The grain size range
varies from 10‐15 μm and 15‐25 μm of the ceramics
sintered at 8h and 12h, respectively. It can be seen that
the grain size increased with increase of sintering time
and the correspondingly grain boundary was reduced.
Increasing the sintering time significantly promotes the
grain growth and microstructural densification. The
microstructures show grain growth in the specimen
sintered for 8h and 12h along with some liquid phase.
Additionally, a small amount of CuO phase was found in
grain boundary region. This phase was so small that XRD
could not detect. It also seems that with increasing
sintering time from 6h, 8h and 12h solid CuO phase start
melting as shown in Fig. 3(b) and totally melted in at
grain boundary as shown in Fig. 3(c). Copper oxide
present at grain‐boundary transforms into the liquid
phase during sintering which leads to abnormal grain
growth [23‐24].