Electr
olyte materials with c
omp
ositi
on La
2M
o2−yW
yO
9 (
y = 0–1.5) exhibit high i
onic c
onductivity ranging fr
om 0.11 S cm
− 1 (
y = 0) t
o 0.05 S cm
− 1 (y = 1.5) at 1023 K, which is c
omparable t
o gad
olinia d
oped ceria. The i
onic c
onductivity is pred
ominant in a wide range
of
oxygen partial pressures fr
om 0.21 t
o 10
− 20 atm at 973 K with i
onic transp
ort numbers higher than 0.95 under humidified 5%H
2–Ar. Ab
ove this temperature, a significant increase
of the n-type electr
onic c
onductivity and degradati
on
of the ceramic micr
ostructure are
observed as a c
onsequence
of the cell v
olume expansi
on in additi
on t
o the f
ormati
on
of new phases up
on reducti
on. C
onsidering the p
otential use
of these materials as s
olid electr
olytes, the chemical c
ompatibility with m
ost
of the typical electr
odes c
omm
only used in SOFCs (e.g. c
obaltites, ferrites, chr
omites and manganites) was investigated. Severe chemical reacti
on was f
ound between La
2M
o2−yW
yO
9 and m
ost
of the studied electr
odes, mainly due t
o m
olybdenum migrati
on. Furtherm
ore, the high thermal expansi
on c
oefficients
of La
2M
o2O
9 based materials (
om/scidirimg/entities/223c.gif" alt="n
ot, vert, similar" b
order=0> 15 · 10
− 6 and
om/scidirimg/entities/223c.gif" alt="n
ot, vert, similar" b
order=0> 20 · 10
− 6 K
− 1 in the l
ow and high temperature range, respectively) restrict the ch
oice
of c
ompatible materials as cell c
omp
onents. M
ore
over, electr
olyte and electr
odes present p
oor c
ontact due t
o the l
ow fixing temperature, necessary t
o prevent excessive chemical reacti
on between the materials, and als
o the large thermal expansi
on c
oefficients
of lanthanum m
olybdate materials, resulting in the separati
on
of b
oth materials after several c
onsecutive thermal cycles. Theref
ore, the use
of these materials as SOFC electr
olyte seems t
o be rather limited.