SÍNTESE E CARACTERIZAÇÃO DE COMPÓSITOS COM CONDUTIVIDADE MISTA IÔNICA E PROTÔNICA

Abstract

Solid oxide fuel cells (CaCOS) are considered to be promising sources of clean energy. They are devices capable of converting chemical energy into electrical energy, reaching efficiency of around 70%, which is why the interest of research aimed at this type of fuel cell. The present work sought to synthesize and characterize materials with mixed proton and ionic conductivity for a possible use as electrolyte for CaCOS. The strategy was to obtain a composite material formed by a proton conductive phase BaCe0,2Zr0,7Y0,1O3-δ (BCZY) and an ionic conductive phase of Sm0,2Ce0,8O1,9 (SCO). The BCZY was synthesized by the modified Pechini method and calcined at 900ºC for 4 hours. The SCO was used commercial powder. We studied 3 compositions (in % by weight) were studied: 30% BCZY and 70% SCO (B3S7), 50% BCZY and 50% SCO (B5S5) and 70% BCZY and 30% SCO (B7S3). The composites were sintered at temperatures of 1400ºC and 1500ºC for 4h and characterized by measurements of apparent density, apparent porosity, X-ray diffraction, scanning electron microscopy with dispersive energy spectroscopy and impedance spectroscopy. The electrical measurements associated to the X-ray diffraction results show that it was possible to form the composites with two phases, one proton conductive and one ionic conductive, using the BCZY and SCO phases, and that the composites presented mixed proton/ionic conductivity. The results of the electrical measurements correcting the effect of porosity by the Archie equation show that the B3S7 composite presented the highest conductivity values among the 3 composites studied.