Effects of rare earth oxides on microstructures and thermo-physical properties of hafnia ceramics

•The sintering resistance and thermo-physical properties of rare earth oxides multi-doped hafnia ceramics were investigated.•The co-doping of Yb-Y significantly improved sintering resistance of the ceramics.•Thermal conductivity of Yb6Y18 is as low as 1.4 W m−1 K−1 while TEC is as high as 10.3 × 10-6 K−1.