Tailoring the initial characterization of fully stabilized HfO₂ with Y₂O₃/Ta₂O₅

New ceramic materials for thermal barrier coating (TBC) are a key to more powerful and efficient next-generation gas turbines. Here, we investigate the effect of the two novel dopants, Ta₂O₅ and Y₂O₃, on the phase stability, thermophysical and mechanical properties of the HfO₂-based ceramic systems (i.e., Ta₂O₅-HfO₂; Y₂O₃-HfO₂). For the Ta₂O₅-HfO₂ system, we observe the formation of a new compound, Hf₆Ta₂O₁₇. In the Y₂O₃-HfO₂ system, stabilized HfO₂ with up to 18 mol% YO_1.5 (YSH) is generated, whereby monoclinic HfO₂ transforms to cubic HfO₂. The cubic YSH ceramics demonstrate enhanced phase stability, compared with Hf₆Ta₂O₁₇ at temperatures up to 1300 °C. The mechanical properties, thermal expansion and fracture toughness of 18–24 mol% YSH (YO_1.5 = 18–24 mol%) indicate that cubic YSH exhibits enhanced suitability for higher-temperature.