In this paper, the phase stability of 50wt% gadolinium zirconate (Gd2Zr2O7, GZ) and 50wt% yttria-stabilized zirconia (YSZ) powder mixture heat treated at 1300 °C for different time was investigation by X-ray diffraction (XRD). Results showed that due to the gadolinium and yttria ion diffusion, the lattice parameter of GZ decreased with increase of the heat treatment time, and a part of YSZ had phase transformation which might be one of the reasons for the interface failure in double-layered or functionally gradient TBC systems. In addition, the room-temperature hemispherical reflectance, transmittance and absorptance spectra over the wavelength range from 0.8 to 15 μm were also determined for free standing GZ, YSZ and 50wt% GZ+50wt% YSZ plasma sprayed coatings. All of the ceramic coatings are semitransparent due to the high transmittance in the wavelength range <6 μm where turbine engine thermal radiation is concentrated. GZ is transparent to longer wavelengths than 8YSZ and has unique small peaks at wavelength 2.4 μm. The mixed coating is intermediate in behavior to GZ and YSZ coatings.

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