Fabrication of yttria stabilized zirconia coatings by a novel slurry method

By adopting a ‘bricks and mortar’ approach, yttria stabilized zirconia (YSZ) coatings were produced on Fecralloy substrates by a novel slurry method. The slurry contained large preformed particles of 10–60 μm, as the ‘bricks’, and concentrated nano-particle slurry, as the ‘mortar’. Green coatings were prepared by spreading the slurry on substrates. Then sintering at 1200 °C was carried out to produce coatings with grain size up to 200 nm. The presence of larger preformed particles hindered the shrinkage of the coatings during drying and sintering. It was observed that the ‘mortar’ could form inter-preformed particle ‘bridging’, an underlying mechanism for the formation of ‘cemented’ preformed particle network. By using different preformed particles, different micro-architectures were obtained and reduced thermal diffusivities were achieved. The microstructure and density of the coatings can also be modified by infiltration of the nano-slurry.