ChemInform Abstract: Oxygen‐Deficient R₂MoO_6‐δ (R: Tb, Dy, Y, Ho, Er, Tm, Yb) with Fluorite Structure as Potential Anodes in Solid Oxide Fuel Cells.

Abstract

Oxygen-Deficient R 2 MoO 6-δ (R: Tb, Dy, Y, Ho, Er, Tm, Yb) with Fluorite Structure as Potential Anodes in Solid Oxide Fuel Cells. -The title compounds are synthesized by solid state reaction of stoichiometric mixtures of Ln2O3 (Ln: Y, Dy, Ho, Er, Tm, Yb) and MoO3 (air, 1150°C, 12 h) followed by treatment in 5% H2/N2 (900°C, 12 h). The products are characterized by neutron powder diffraction, thermal expansion and electrical conductivity measurements. The highly oxygen-deficient compounds crystallize with the fluorite-type structure in the cubic space group Fm3m with Z = 4. The electrical conductivity shows a semiconducting-like behavior with the maximum conductivity value for the Tb compound. The materials are expected to present mixed ionic/electronic conductivity with thermal expansion coefficient values that perfectly match those of the usual solid oxide fuel cell electrolytes. They are therefore potential anode materials for intermediate temperature solid oxide fuel cells. -(AGUADERO*, A.; MARTINEZ-LOPE, M. J.; POMJAKUSHIN, V.; ALONSO, J. A.; Eur. J. Inorg. Chem. 2011, 21, 3226-3231, http://dx.

On the Complex Structural Picture of the Ionic Conductor Sr6Ta2O11

“…The secondary phase was not observed in the XRPD pattern, since the common laboratory XRPD used cannot distinguish such a minor phase. High diffuse background of the NPD patterns, but not of the XRPD pattern, is similar to what has been observed for various oxide ion conductors by NPD, − and it has been described as substantial disorder of the oxygen sublattice.…”

Metal-Doping of La5.4MoO11.1 Proton Conductors: Impact on the Structure and Electrical Properties

“…The unit cell volume of the quenched samples decreases linearly along the series, according to Vegard’s law, due to the smaller ionic radii of Nb 5+ (0.74 Å) in an 8-fold coordination, in comparison to those of La 3+ (1.16 Å) and Mo 6+ (1.02 Å) in the same environment (Figure S2). It has to be noted that the ionic radii of Mo 6+ in 8-fold coordination is not reported in Shannon’s database; therefore it has been estimated from the Mo–O distances of several molybdenum-containing compounds: La 2.4 Mo 1.6 O 8 (ICSD 27006), Ho 2 MoO 4.8 (ICSD 261709), Bi 3.2 Mo 0.8 O 7.5 (ICSD 38357), and Mo 3 O (ICSD 15903), all of them with an Fm 3̅ m space group. − …”

Structural Features and Physical Properties of Tetragonal Ln2MoO6 (Ln = La, Pr) Oxymolybdates Doped with Cadmium Atoms

“…In several works, cubic oxygen-defective molybdates Ln 2 MoO 6−δ with fluorite structure for monoclinic Ln = Gd, Tb, Dy, Ho, and Y, Ln = Tb–Yb, and tetragonal lanthanum molybdate La 2 MoO 6 were prepared under reducing conditions. The authors reported on the high conductivity of such compounds, which makes using it as anode materials in SOFCs possible.…”