On the synthesis and performance of flame-made nanoscale La 0.6Sr 0.4CoO 3− δ and its influence on the application as an intermediate temperature solid oxide fuel cell cathode

Abstract

Flame spray synthesis (FSS), a large-scale powder processing technique is used to prepare nanoscale La 0.6Sr 0.4CoO 3− δ powder for solid oxide fuel cell cathodes from water-based nitrate solutions. Influence of processing is investigated on basis of the as-synthesised powders by X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), nitrogen adsorption (BET) and electron microscopy (SEM and TEM). Against the background of a nanostructured cathode morphology for an intermediate temperature solid oxide fuel cell (IT-SOFC) at 600 °C, an optimised and high surface area flame-made La 0.6Sr 0.4CoO 3− δ nanopowder of 29 m 2 g −1 is used to investigate its performance and chemical reaction with common electrolytes (Y 0.16Zr 0.84O 2− δ , Ce 0.9Gd 0.1O 2− δ and Sc 0.20Ce 0.01Zr 0.79O 2− δ ). Secondary phase analysis from XRD measurements revealed a substantially lower La 2Zr 2O 7 and SrZrO 3 formation in comparison to conventional spray pyrolysed and submicron powder of about 9 m 2 g −1. TGA and resistivity measurements proofed that La 0.6Sr 0.4CoO 3− δ is non-sensitive towards carbonate formation under CO 2 containing atmospheres. Electronic bulk conductivity of 2680 S cm −1 (600 °C) and 3340 S cm −1 (500 °C) were measured in air and as function of oxygen partial pressure (2 × 10 5 Pa > p(O 2) > 1.2 × 10 −2 Pa) in the temperature range between 400 and 900 °C. Electrochemical performance is determined by impedance spectroscopy on symmetrical cells of screen printed nanoscale La 0.6Sr 0.4CoO 3− δ on Ce 0.9Gd 0.1O 2− δ substrates from which an area specific resistance (ASR) of 0.96 Ω cm 2 at 600 °C and 0.14 Ω cm 2 at 700 °C were obtained.