Electrical properties and oxygen diffusion in yttria-stabilised zirconia (YSZ)–La 0.8Sr 0.2MnO 3± δ (LSM) composites

Abstract

Dense YSZ–LSM composites were fabricated for application as an oxygen separation membrane. A density about 95% was achieved for a sintering temperature of 1350 °C; however, an insulating La 2Zr 2O 7 phase was formed during this high-temperature sintering. The percolation threshold was identified at about 30 wt.% (or 28 vol.%) of LSM. Isotopic exchange depth profiling (IEPD)/secondary ion mass spectrometry (SIMS) method was used to investigate the oxygen diffusion and surface exchange properties of the composites. The two composites, YSZ–30 wt.%LSM and YSZ–40 wt.%LSM (or 38 vol.% LSM), with a 3-D interconnected network, had higher oxygen diffusivity than the pure LSM, but slightly lower than the parent YSZ material. The oxygen surface exchange coefficient of the YSZ was significantly enhanced by the introduction of the electronic conductor LSM, which confirmed the supposition that the availability of electrons limits the oxygen surface exchange reaction on the pure YSZ materials.