Deposition of thick and 50% porous YpSZ layer by spraying nitrate solution in a low pressure plasma reactor

The deposition of Yttria partially Stabilized Zirconia (YpSZ) for Thermal Barrier Coating application (TBC) is a current topic of interest. The TBC must exhibit high thickness (100–300 μm), vertical cracks in order to be a strain tolerant layer, and high porosity to decrease the thermal conductivity. In this paper, a solution of nitrate salt is introduced into a low pressure plasma discharge (600 Pa, 80–220 W) to obtain YpSZ layers.Several analytical techniques were used to study the characteristics and the stability of the YpSZ layers obtained in the low pressure plasma reactor. Optical emission spectroscopy indicated that the oxidant chemistry in the plasma is responsible for the formation of the oxide and the elimination of the nitrates at low temperature (T < 300 °C on the layer). SEM, water porosimetry, thermal diffusivity and XRD analyses were performed to study the effect of the parameters (power of the plasma discharge, post-treatment, heat treatment) on the structure, the morphology and the stability of YpSZ coatings. For example, it was observed that YpSZ is 50% porous in all cases and that the nanostructures of the coating resist against high temperature conditions (1200 °C/5 h).