82
2 – Methods and techniques
.
a
02
O
CE
2
=
The ionic conductivity of the sample is calculated from the expression
(a )
2 a
1
dU
dI
i O
WE
2
σ
π
=
#
The factor dI/dU is obtained by calculating the derivative of the analytical
expression for current as a function of the applied potential determined above:
.
dU
dI
U
U
U
2 8 10
9 10
2 10
3 10
5
3
6
2
7
8
= −
+
−
+
−
−
−
−
#
#
#
#
#
#
#
with U in V and I in A.
The results for the oxygen activity a O
WE
2
and the ionic conductivity σ i of the
sample for each value of the applied potential appear in table 21.
Table 21 – Logarithm of oxygen activity and of the ionic
conductivity of LSCo as a function of applied potential U.
U [V]
− 0.160 − 0.140 − 0.120 − 0.100 − 0.080 − 0.060 − 0.040 − 0.020
log a O
WE
2
− 4.39 − 3.93 − 3.47 − 3.01 − 2.55 − 2.08 − 1.62 − 1.16
log σ i [S cm
−1
] − 5.19 − 5.30 − 5.43 − 5.57 − 5.73 − 5.89 − 6.06 − 6.22
U [V]
0
0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160
log a O
WE
2
− 0.70 − 0.24 0.22 0.69 1.15 1.61 2.07 2.53 3.00
log σ i [S cm
−1
] − 6.32 − 6.33 − 6.26 − 6.15 − 6.04 − 5.94 − 5.86 − 5.79 − 5.74
4. Figure 34 shows the ionic conductivity of LSCo as a function of oxygen
activity.
<
<
<
<
<
<
<
<
<
<
ORJı
L >ı
L LQ6FP
<
@
:(
ORJD 2
9 2
‡‡
2 L ƍƍ
Figure 34 – Ionic conductivity of LSCo as a function of oxygen activity.