Page 53 - High Temperature Solid Oxide Fuel Cells Fundamentals, Design and Applications

34 High Temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications

the platinum anodes, which did not withstand long-term current loading; they
tended to peel off from the electrolyte, probably due to the water vapour formed
between the electrolyte and the anode layer.
In Europe, in 19 5 8 Palguyev and Volchenkova published conductivity
measurements on 3Zr022Ce02 + 10 wt% CaO and other systems [60]. From
1960 onwards, results of a broadly based research programme on cells with solid
oxide electrolytes appeared from the Ural branch of the Academy of Sciences
of the USSR [61] under the leadership of Karpachov. Tannenberger et a].,
starting in 19 5 9 at the Battelle Institute in Geneva, presented a thin film fuel cell
concept in a 1962 patent, where a porous ceramic support tube was used as a
structural member [62]. From the Battelle Institute in Frankfurt, Sandstede gave
in September 1962 the first report on the use of hydrocarbons as a fuel in solid
oxide cells, applying a converter containing Ni gauze as catalyst upstream of the
cells (discs of Zro.ssCao.1501.85, diameter 22 mm, with porous Pt layers), and
compared measurements with theoretical calculations [63]. At about the same
time, fuel cell work was started in France by Kleitz [64], and in Britain, a patent
was filed in August 1963 [65] to form fuel cells by depositing layers on a porous
metallic carrier.
In Japan, Takahashi, after investigations with alkali carbonate electrolytes,
published in 1964 his first results obtained on fuel cells with solid oxide
electrolytes [66].
Surveys of these activities were presented at the international fuel cell
meetings in 1965, 1967 and 1969 in Brussels. In 1965, results on solid oxide
fuel cells were published by General Electric [67], by the Battelle Institute in
Geneva [68,69] and by the universities of Grenoble [70], Nagoya [71] and
Greifswald [ 5 11. Most developments began with conductivity measurements
for optimising the solid electrolytes. Even very expensive rare earths, such
as ytterbium oxide, were used [72] to achieve highest conductivities, and
ternary systems were investigated to reduce costs (Zr02-Y203-Yb203 [ 731,
Zr02-Y203-Mg0 [74]). As a rule, A1203 was added to achieve gastight, dense
sintering products [ 72-75]. This provoked investigations of the effect of grain
boundary conductivity in electrolyte materials [ 761.
The mobility of the oxide ions in Zro.s5Ca~.lsOl.ss was determined using
the l80/l6O isotope exchange between solid and gas phase by IGngery ef aI. in
1959 [77] and more precisely by Simpson and Carter in 1965 [78]. In 1962,
Schmalzried showed by X-ray intensity measurements that the Zr and Ca cations
occupy random sites in the cation sublattice of Zro.ssCao.1501.85 [79]. In 1963,
decrease in conductivity with time was seen as a sign of aging of the oxide ion
conductors, caused by disorder-order transitions, in which the random
distribution ofthe cations and oxide ions in the lattice changed to an ordered state
[80,8 I]. Alterations of the composition influenced the effect substantially [82].
Several measurements confirmed the influence of the cation size on the
conductivity of mixed oxides with fluorite structure [68,83-851. These results
and also the determination of the ion mobilities in Na2S, which possesses
antifluorite structure and reaches the highest known sodium ion conductivity
[ 8 61, supported the space-geometrical considerations [48] corresponding to