Biomedical Engineering Reference
In-Depth Information
Figure 14.3
Scanning electron micrographs of sintered composition (1170 C).
8
6
4
2
1
0
1
2
3
z ×10
2
0
0
1
2
3
4
5
z ×10
3
Figure 14.4
Complex-plane impedence plots for present material at 443 K.
In general, for a perfect crystal the values of resistance R and capaci-
tance C can be analyzed by an equivalent circuit of one parallel resistance-
capacitance (RC) element. h is RC element gives rise to one semicircular
arc on the complex plane and has intercepts on the Z axis of zero and R.
h us C can be calculated with the relation ω
m
RC = 1, where ω
m
= 2πν
m
and ν
m
is the frequency at the arc maxima. For a bulk crystal contain-
ing interfacial boundary layers, the equivalent circuit may be considered
as two parallel RC elements connected in series and giving rise to two
arcs in complex plane: one for the bulk crystal (grain) and the other for
the interfacial boundary (grain-boundary) response. h e relative posi-
tion of the two arcs in the complex plane can be identii ed by the fre-
quency. h e arc of bulk generally lies on a frequency range higher than
