Preparation of YSZ/Al2O3 composite coatings via electrophoretic deposition of nanopowders

Abstract

Using electrophoretic deposition (EPD), we have produced YSZ individual ceramic coatings and YSZ/Al₂O₃ composite coatings for a wide range of applications in modern materials research. YSZ and Al₂O₃ nanopowders were prepared by high-energy physical dispersion techniques, namely, by a laser evaporation–condensation process and electroexplosion of wire, respectively. Stable nonaqueous suspensions for the EPD process have been prepared using YSZ and Al₂O₃ nanopowders with an average particle size of 11 and 22 nm, respectively. The YSZ/Al₂O₃ composite coating produced by sintering at 1200°C has been shown to have higher density in comparison with the YSZ individual coating produced at the same temperature. X-ray diffraction characterization showed that the YSZ/Al₂O₃ composite coating consisted of two crystalline phases: α-Al₂O₃ (corundum) (42 wt %) and cubic ZrO₂〈Y₂O₃〉 (58 wt %). Quantitative analysis of electron micrographs of the surface of the films showed that the YSZ individual coating produced by sintering at 1200°C had a loose structure and contained pores (9%), as distinct from the composite coating, which had a dense, porefree grain structure.