In this work we are to report the results of our recent development in the field of powder synthesis and coating production with lanthanum and gadolinium zirconates and their thermal properties investigation. Spray drying route was chosen to prepare powders with inorganic salt solutions being the precursors. The powders obtained were analyzed by means of SEM, XRF (WDS), XRD, DSC and laser diffraction. To obtain coatings air plasma spray (APS) equipment was used. The structure and properties of coatings were studied using SEM, XRF (WDS), XRD, DSC, and LFA techniques.It was shown that during the spraying process and subsequent thermal treatment phase transitions and microstructure evolution occur. Obtained powders have the pyrochlore structure, but due to rare earth oxide evaporation during the spraying process and due to high cooling rate most of the coatings acquire the defect fluorite structure. Thermal conductivity of as-sprayed coatings was shown to be very low (0.35-0.50 VV/mK at 1000°C). Then, during the heat treatment microstructure evolution, crystal structure ordering and phase transition processes occurred strongly affecting the thermal properties of coatings (> 100% conductivity growth during first ~20 hours). This "initial growth" value is completely different for all advanced TBC materials. The present paper focuses specifically on data for lanthanum and gadolinium zirconates.
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