Microstructure, Mechanical Properties, and Pyroconductivity of NiFe2O4 Composite Reinforced with ZrO2 Fibers

NiO-Fe2O3-ZrO2f composites were fabricated by a two-step sintering process. No phase transformation for ZrO2f was observed. The as-prepared NiO-Fe2O3-ZrO2f ceramic showed excellent mechanical properties because of the introduction of ZrO2 fiber. The values for both the bending strength and fracture strength of 3 wt.% ZrO2f-reinforced NiFe2O4 samples reached the maximum values of ~89.0 MPa and ~4.67 MPa m1/2, respectively, The toughness mechanism is mainly attributed to fibers’ fracture, crack deflection, fibers’ pull-out, and fibers’ debonding. The conductivity of ZrO2f-reinforced NiFe2O4 is dependent on temperature and ZrO2f content. When the electrolytic temperature is up to 950 °C, the conductivity value of the sample reinforced with 4 wt.% ZrO2 fibers is 0.63 S/cm, which has been improved by 37.8% compared with the conductivity value of 0.45 S/cm for the un-doped samples. The main conductive mechanisms of ZrO2 fiber in the matrix are the one based on the substitution of Zr4+ ions to produce quasi-free electrons, and the other based on oxygen ionic conducting mechanism.