Twin-Structured Yttria-Stabilized t′ Zirconia Coatings Deposited by Plasma Spray Physical Vapor Deposition: Microstructure and Mechanical Properties

In this work, we report a twin‐structured yttria‐stabilized t′ zirconia (YSZ) coating which was fabricated through an advanced plasma spray physical vapor deposition process with a high‐power hybrid plasma spraying system. The as‐deposited YSZ structure, entirely different from those deposited by conventional atmospheric plasma spraying and electron beam physical vapor deposition, is characterized by coarse grains of over 5 μm size which compose the entire coating, differently sized t′‐ZrO2 twins which fill the coarse grains, and micron‐scaled lenticular t′ colonies in which twins on the submicrometer scale arrange alternatively. The indentation tests show that both the nanohardness and microhardness of the peculiar coating are markedly higher than those of the ordinary YSZ coatings, even comparable with those of the sintered YSZ polycrystal bulks.