On the synthesis and performance of flame-made nanoscale La0.6Sr0.4CoO3−δ and its influence on the application as an intermediate temperature solid oxide fuel cell cathode

Flame spray synthesis (FSS), a large-scale powder processing technique is used to prepare nanoscale La0.6Sr0.4CoO3−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 La0.6Sr0.4CoO3−δ nanopowder of 29 m2 g−1 is used to investigate its performance and chemical reaction with common electrolytes (Y0.16Zr0.84O2−δ, Ce0.9Gd0.1O2−δ and Sc0.20Ce0.01Zr0.79O2−δ). Secondary phase analysis from XRD measurements revealed a substantially lower La2Zr2O7 and SrZrO3 formation in comparison to conventional spray pyrolysed and submicron powder of about 9 m2 g−1. TGA and resistivity measurements proofed that La0.6Sr0.4CoO3−δ is non-sensitive towards carbonate formation under CO2 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 × 105 Pa > p(O2) > 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 La0.6Sr0.4CoO3−δ on Ce0.9Gd0.1O2−δ substrates from which an area specific resistance (ASR) of 0.96 Ω cm2 at 600 °C and 0.14 Ω cm2 at 700 °C were obtained.