Effects of Yb3+ doping on phase structure, thermal conductivity and fracture toughness of (Nd1-xYbx)2Zr2O7

Abstract To investigate the effects of Yb3+ doping on phase structure, thermal conductivity and fracture toughness of bulk Nd2Zr2O7, a series of (Nd1-xYbx)2Zr2O7 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) ceramics were synthesized using a solid-state reaction sintering method at 1600 °C for 10 h. The phase structures were sensitive to the Yb3+ content. With increasing doping concentration, a pyrochlore-fluorite transformation of (Nd1-xYbx)2Zr2O7 ceramics occurred. Meanwhile, the ordering degree of crystal structure decreased. The substitution mechanism of Yb3+ doping was confirmed by analyzing the lattice parameter variation and chemical bond of bulk ceramics. The thermal conductivities of (Nd1-xYbx)2Zr2O7 ceramics decreased first and then increased with the increase of Yb3+ content. The lowest thermal conductivity of approximately 1.2 W m−1 K−1 at 800 °C was attained at x = 0.4, around 20% lower than that of pure Nd2Zr2O7. Besides, the fracture toughness reached a maximum value of ~1.59 MPa m1/2 at x = 0.8 but decreased with further increasing Yb3+ doping concentration. The mechanism for the change of fracture toughness was discussed to result from the lattice distortion and structure disorder caused by Yb3+ doping.