Flame spray synthesis and characterisation of stabilised ZrO2 and CeO2 electrolyte nanopowders for SOFC applications at intermediate temperatures

Abstract

Zirconia (Y0.16Zr0.84O2, Sc0.2Zr0.8O2 and Sc0.2Ce0.01Zr0.79O2) and ceria (Gd0.2Ce0.8O2) based electrolyte materials are synthesised at production rates up to 260 g h−1 by a liquid-fed one-step flame spray synthesis from water-based solutions, or cost-effective rare earth nitrates with a high water content. It was found that this one-step synthesis, based on an acetylene-supported flame is able to produce phase pure and highly crystalline, nanoscale electrolyte materials. The as-synthesised powders show a cubic lattice structure independent of production rates. Specific surface areas of the powders were adjusted between 20 and 60 m2 g−2, where the latter is an upper limit for the further processing of the powders in terms of screen printing. The influence of process parameters on morphology, particle size, composition, crystallinity, lattice parameter, shrinkage behaviour and coefficient of thermal expansion of the as-synthesised powders were systematically investigated by transmission electron microscopy (TEM), nitrogen adsorption (BET), X-ray diffraction (XRD) and dilatometry. Electrochemical impedance spectroscopy (EIS) was applied at temperatures between 300 °C and 900 °C and confirmed the high quality and the competitive electrochemical behaviour of the produced powders.