Eletrólitos sólidos homogêneos e heterogêneos : obtenção e caracterização visando aplicação em células A combustível de temperatura intermediária

Abstract

Emission reduction of greenhouse gases to the atmosphere in order to control global warming is an urgent need fully accepted by the international community. Ceramic materials play an important role in the possible solutions for this problem, with emphasis on 8 mol% Yttria-Stabilized Zirconia (8YSZ). 8YSZ is the state of the art material for high temperature Solid Oxide Fuel Cell (SOFC) electrolytes, however its ionic conductivity is not high enough to enable cell operation at intermediate temperatures (T~600°C), which are considered to be optimal for technological feasibility, considering cost, efficiency and life span. The goal of this work was to investigate the role of new interfaces in electrolytes with 8YSZ as the major phase, in order to obtain ceramic materials with unique microstructures, as well as higher conductivity than conventional ones. In order to achieve this goal, the following were investigated: i) homogeneous composite consisting of 8YSZ single crystals dispersed and oriented in 8YSZ polycrystalline matrix; ii) heterogeneous composite formed by Al2O3 single crystals (sapphire) dispersed and oriented in 8YSZ polycrystalline matrix; iii) heterogeneous composite consisting of intercalated layers of 8YSZ and Al2O3 polycrystalline films, which were deposited on Al2O3 mono and polycrystalline substrates. All analyzed systems showed higher electrical conductivity than 8YSZ samples with conventional microstructure. Emphasis should be made to the homogeneous composite (8YSZ polycrystalline matrix with 8YSZ monocrystalline fiber oriented) which showed electrical conductivity 18 times higher than 8YSZ with conventional microstructure, which can enable SOFC operation at intermediate temperatures.