Influence of number of layers on thermal properties of nano-structured zirconia film fabricated by EB-PVD method

This work describes the experimental results of thermal conductivity and thermal diffusivity of the multi-layered ZrO2-4 Mol%Y2O3 (YSZ) film to develop the low thermal conductive thermal barrier coating. YSZ films with 2 similar to 5 layers were deposited on zirconia substrates by Electron Beam-Physical Vapor Deposition (EB-PVD). The YSZ layers consist of porous-columnar grains containing nano-pores. It is noted that multi layers contain residual pores at interface between layers. Density and thermal diffusivity of the multi-layered YSZ film decreased with increasing the number of layers. Consequently, the thermal conductivity of films decreased with increasing the number of layers. The decrease of thermal conductivity in multi layers is caused by increase of total porosity due to increase of the layer-interface pores, resulting the increase of the phonon scattering.