Microstructure Characterization and Thermal Conductivity Analysis of Plasma Sprayed ZrO₂ Coatings

Yttria stabilized zirconia coatings were deposited using two different sets of parameters (N1, N2 coating). The microstructure features, such as total porosity and large porosity, were quantified by means of scanning electron microscope and image analysis. The three-dimensional distribution of microcracks and segmentation cracks was successfully revealed by the X-ray microscopy in the scanning electron microscope with three-dimensional microtomography capability. So the relationship between microstructure and thermal conductivity was found. At room temperature, thermal conductivity of N2 was lower than that of N1 due to larger pores and microcracks. At 1000℃ thermal conductivity of N1 was lower for the sintering of microcracks. The segmentation cracks formed by the propagation of microcracks could effectively reduce the thermal conductivity at high temperature.