title: Synthesis and characterization of nonsubstituted and substituted proton-conducting La(6-x)WO(12-y).
abstract: Mixed proton-electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic-electronic conductivity. Lanthanum tungstate La(6-x)WO(12-y) (with y = 1.5x + δ and x = 0.5-0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La(6-x)WO(12-y) and for all substituted La(6-x)WO(12-y) compounds was measured in the temperature range of 400-900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM.
authors.affiliation: Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research IEK-1 , D-52425 Jülich, Germany.
authors.forename: Janka
authors.initials: J
authors.lastname: Seeger
authors.forename: Mariya E
authors.initials: ME
authors.lastname: Ivanova
authors.forename: Wilhelm A
authors.initials: WA
authors.lastname: Meulenberg
authors.forename: Doris
authors.initials: D
authors.lastname: Sebold
authors.forename: Detlev
authors.initials: D
authors.lastname: Stöver
authors.forename: Tobias
authors.initials: T
authors.lastname: Scherb
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schumacher
authors.forename: Sonia
authors.initials: S
authors.lastname: Escolástico
authors.forename: Cecilia
authors.initials: C
authors.lastname: Solís
authors.forename: José M
authors.initials: JM
authors.lastname: Serra