116
3 – Transport in ionic solids
<
<
<
<
ORJ>L@
ORJ3 2 >3 2 LQ3D@
>9 2
‡‡
@
>+ L
‡
@
S
@
> @ >
9
9
6U
=U
l
ll
Figure 47 – Concentration of point defects as a function of oxygen partial pressure
in the presence of water vapor at 800 °C (from Labrincha, Frade & Marques, 1993).
3. Justify the equation for the variation of [H
•
i ] with oxygen partial pressure
(see fig. 47).
Data
2H 2  + O 2  m 2H 2 O
with
Δ r  G ° T = − 494 + 0.112 T [kJ mol
−1
]
4. We dope SrZrO 3 with yttrium oxide Y 2 O 3 to obtain a solid solution
SrZr 1−x Y x O 3−0.5x .
a. Write the doping reaction and the equation for electroneutrality.
b. State the conditions that would allow an oxygen partial pressure domain
where [Y ′
Zr ], [V ′′ Sr ], [V
4 ′
Zr ], and [V
••
O ] are constant.
c. For these conditions, give the equation that approximately relates [H
•
i ]
to [V
••
O ] and comment on the type of ionic conduction.
C – Determination of electronic conduction part
1. We make the following cell:
H 2 (P H 2, 1 = 1 bar),Pt / SrZr 0.95 Y 0.05 O 3−α / Pt,H 2 (P H 2 ,c )