Thermal conductivity of nanoporous ZrO2–4 mol% Y2O3 multilayer coatings fabricated by EB-PVD

The effect of multilayer configurations on the thermal conductivity of 4 mol% Y2O3− stabilized ZrO2 coatings fabricated by EB-PVD has been investigated. The deposited coating layers consist of columnar grains containing nano-sized pores. Multilayer specimens are found to contain many pores at the interfaces between layers. The density and thermal conductivity of the multilayer coatings decreases with increasing number of coating layers for one to six layers. The thermal conductivities of coatings deposited onto rotating substrates are lower than those of coatings deposited on stationary substrates. The decreased thermal conductivity of multilayer coatings is ascribed to the increased total porosity resulting from an increase in the number of interface pores concomitant with the formation of non-uniform interfaces between layers, which causes increased phonon scattering.