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Nickel superalloy used for gas turbine blades was coated with a ceramic thermal barrier by powder spraying. For formation of the sublayer and the surface layer, the AMDRY 962 and the YSZ METCO 204B-NS powders were used, respectively. Microanalysis of chemical and phase composition of the powders as received and after plasma spraying were carried out. The original sublayer powder was composed of Ni(Cr) phase (about 71 %), NiAl phase (25.5 %) and Ni5Y phase (3.5 %). In the YSZ powder, various crystallographic forms of ZrO2 were found. It consisted of monoclinic (7.5 %), tetragonal (37 %) and cubic (55 %) phases. After spraying, the content of monoclinic phase was increased to 10 %. After 100 thermal cycles at 1100 deg C, only the cubic phase was found. Thermal cycling resulted in spalling of the coating along the sublayer-surface layer interface because of the cumulation of microcracks, sintering the ceramics and interlayer oxidation, what is characteristic for plasma-sprayed coatings.