Y–Al–O thermal barrier coating was investigated using synchrotron radiation. Y–Al–O coating was deposited on molybdenum substrate using cathodic-arc deposition with two elemental cathodes made from aluminum and yttrium respectively. Phase evolution was investigated during samples heating up to 1500°C in vacuum. It was found that as-deposited coating has amorphous structure and crystallization process take place at 1160–1170°C, no another phase transformations was observed. Qualitative phase composition of coating as well as microstresses in film were determined. The results of evaluation demonstrates lack of microstresses in obtained coating. Obtained results demonstrates a possibility of Y–Al–O coating deposition by cathodic arc deposition Arc-PVD technology, and deposited coating consist of YAlO3 (predominantly), Y2O3 oxides and YAl2 intermetallic.