Proton conductors based on alkaline-earth substituted La28−xW4+xO54+3x/2
2014; Royal Society of Chemistry; Volume: 43; Issue: 17 Linguagem: Inglês
10.1039/c3dt53604a
ISSN1477-9234
AutoresMaría José Zayas-Rey, Lucía dos Santos‐Gómez, Aurelio Cabeza, David Marrero‐López, Enrique R. Losilla,
Tópico(s)Magnetic and transport properties of perovskites and related materials
ResumoLanthanum 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.
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