Prakt. Met. Sonderband 46 (2014) 165
T/°C
875 850 825 800 775 750 725 700 675 650 625 600
EZ EL ALL
/ relaxation | —A-— oxidation
is abruptly —7— reduction
. Nonlinear
xtraction of Le
d chemical - 1E-3 ~~ with An-layer
2d between &
to higher or 2
axperiment, 2
= 1E-4
ring Ag-foil
levice. The
otoelectron i v
in ultrahigh 16-5 4 ke SEEN
jgectrometer 0.90 0.95 1.00 1.05 1.10 1.15
n. Surface 1000 T° / K*
oy use of a
hode at an Fig. 1: Effect of silver-coating on the oxygen surface exchange coefficient kchem of
Laz2NiO4+5 at 0.1 bar pO2. Symbols connected by solid lines represent results obtained
from a bar-shaped sample after silver coating, while dotted lines link data points from
measurements on a reference sample without prior surface modification.
f LazNiOa+s T/°C Tic
B75 850 825 800 775 750 725 700 675 650 625 600 875 850 825 800 775 750 725 700 675 650 625 600
orresponds Edt AL L te = 1E-2 1B pd. Lp E22
C-cathode. De
| step in the ~~ ES res
s could be . =, N
inetics was | : EE 5 ©. pres 5
c activity of a 3 A ad Lies :
. + 1E-5 2 1E-5 £
s started at — U? a =
850°C was - N 1E-6 E1E-6
| A 0.01 bar —> 0.015 bar pO ] ie 0.1 bar > 0.15 bar pC
¥ 0.015 bar — 0.01 bar pO | 7 0.15 bar — 0.1 bar pC [
of silver at Ek oss 10 10s | tho ams TR im a
cooling run 1000 7 7K" 1000 77 / kK!
[relaxation
noval of the Fig. 2: Arrhenius plots of chemical diffusion and surface exchange coefficients of oxygen
for La2NiOa+s at 0.01 bar pO: (left) and 0.1 bar pO: (right).
ye obtained
cess to the
vo different 3.1 Surface analysis
ined during
are results Visual inspection of the Ag-coated samples after measurement gave no evidence of Ag-
show good residuals on the ceramic surface. Post-test analytical investigations have been performed
. Activation on the surface layer to confirm the complete absence of even trace amounts of silver as well
s of linear as to check whether Ag has been incorporated into the specimen by solid-state diffusion at
for kchem. A elevated temperatures, which might affect the diffusion properties of oxygen within the
by changes material. Penetration of silver from external electrodes into the bulk via diffusion and
