Structure and thermal properties of ZrO2–Ta2O5–Y2O3–Ln2O3 (Ln = Nd, Sm or Gd) ceramics for thermal barrier coatings

The effects of rare earth oxides on the structure and thermal properties of 8.3 mol.% Y2O3 + 8.3 mol.% Ta2O5 co-doped ZrO2 ceramics were investigated. All compositions consisted of only tetragonal (t) phase when 1 mol.% Ln2O3 was substituted for 1 mol.% Y2O3. The introduction of Ln2O3 into the ZrO2–Ta2O5–Y2O3 system resulted in a decrease in grain growth, specific heat capacity and thermal conductivity. Among these oxides Gd2O3 was the most effective oxide in lowering the thermal conductivity of the ZrO2–Ta2O5–Y2O3 system.