Yttria partially stabilized zirconia (YSZ) thick thermal barrier coatings were fabricated by Atmospheric Plasma Spraying (APS) and isothermally annealed at 1315 °C for different durations. The phase composition of as-sprayed and heat-treated free-standing coatings was investigated by X-ray Diffraction (XRD) and the Rietveld method was employed for quantitative phase analysis. High-temperature exposure of YSZ coatings produced the partial decomposition of metastable t′ zirconia phase and the corresponding increase in the amount of stable tetragonal t, cubic c and monoclinic m phases with increasing the aging time. The thermophysical properties of as-sprayed and annealed YSZ coatings, such as thermal expansion and heat capacity, were measured. The thermal expansion coefficient kept almost constant in-plane direction after heat treatment. Otherwise, it changed in through-thickness direction due to any structural changes and high-temperature sintering of the porous microstructure. The sintering also influenced the specific heat capacity Cp which increased with increasing the annealing time. © 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

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