BaCeO3 dopado com 5%Mol Y2O3 : sinterização, microestrutura e condutividade elétrica protônica
Resumen
The development of solid electrolytes for Solid Oxide Fuel Cells is a challenge to
enabling this technology as sustanaible energy resource. Ceramics based on
Yttrium doped- Barium cerate are potential candidates for this application due
high protonic electrical conducitivity at intermediate temperatures, 500~600o C.
In this present work, BaCe0,9Y0,1O3 based ceramics were prepared by solid state
reaction and wet chemical route, specifically amorphous citrate process. The
sintering parameters were controlled by dwell temperature, dwell time and
heating rate. X ray diffraction was performed to powders, green and sintered
ceramics and the perovskite phase was obtained but it was observed that lattice
symmetry shows strongly dependent on dwell sintering and powders preparation
route. The scanning electronic microscopy and sintering at dilatometer were
performed and have shown a liquid phase sintering. A model to BaCe0,9Y0,1O3
sintering was proposed which the partial substitution of Yttrium atoms at host site
of Cerium leads to a liquid phase formation at eutectic point of BaCeO3
composition and this promotes densification. The following step is dedicated to
re-incorporation of Yttrium atoms to lattice and returning to conductive phase.
The success of this step is favored by higher temperatures and chemical
homogeneity of powders. The electrical conductivity shows stronger dependence
on sintering profile at wet chemical powder than at solid state reaction powder.
Among sintered ceramics with density at least 95% than theoretical density, the
higher conductivity was achieved with lower temperature sintering and better
chemical homogeneity, with =10-2 S.cm-1 at 500ºC in humidity atmospheres.