Toughening effect of Yb2O3 stabilized ZrO2 doped in Gd2Zr2O7 ceramic for thermal barrier coatings

Gd2Zr2O7 has been considered as a promising thermal barrier coating candidate for operating above 1300 °C, but the relatively poor fracture toughness limits its application. In this study, effort was made to toughen Gd2Zr2O7 with the addition of metastable tetragonal (t′) phase. For 3.5 mol% RE2O3 (RE=Dy, Y, Er, Yb) stabilized ZrO2 (RESZ) ceramics, the t′ phase stability increased with the decrease of RE3+ ionic radius. Among these compounds, YbSZ exhibited the best phase stability and had excellent toughness, thus it was selected as the toughening agent for Gd2Zr2O7. The phase structure and mechanical properties of YbSZ doped Gd2Zr2O7 were investigated. YbSZ first dissolved in Gd2Zr2O7 lattice, then it presented as a second phase when its content reached to 15 mol%. With YbSZ content increasing, the fracture toughness of the compounds increased, and the related mechanisms were discussed.