title: Proton conductors based on alkaline-earth substituted La(28-x)W(4+x)O(54+3x/2).
abstract: Lanthanum tungstates, "La6WO12", are mixed ion proton-electronic conductors with very interesting properties for technological applications and better phase stability compared to alkaline earth perovskites. A new series of compounds La(27.04-x)M(x)W(4.96)O(55.44-x/2□8.56+x/2) (M = Ca(2+), Sr(2+) and Ba(2+)) are investigated with the aim of increasing the concentration of oxygen vacancies and studying their effects on the structure and transport properties. The materials have been studied by high-resolution laboratory X-ray powder diffraction and scanning electron microscopy combined with energy dispersive spectroscopy (EDS). High temperature X-ray powder diffraction and thermal analysis in wet and dry N2 gas did not show any evidence of phase transition up to 800 °C. The total conductivity was studied by impedance spectroscopy under dry and wet atmospheres and as a function of the oxygen partial pressure. The electronic contribution to the conductivity was determined by the Hebb-Wagner polarization method. The generation of extrinsic vacancies in the lattice with alkaline earth doping leads to a decrease of the ionic conductivity for high doping level, suggesting a proton trapping mechanism.
authors.affiliation: Department of Inorganic Chemistry, University of Malaga, 29071-Malaga, Spain. r_losilla@uma.es.
authors.forename: M J
authors.initials: MJ
authors.lastname: Zayas-Rey
authors.forename: L
authors.initials: L
authors.lastname: dos Santos-Gómez
authors.forename: A
authors.initials: A
authors.lastname: Cabeza
authors.forename: D
authors.initials: D
authors.lastname: Marrero-López
authors.forename: E R
authors.initials: ER
authors.lastname: Losilla