Microstructure and mechanical properties of NiFe2O4 ceramics reinforced with ZrO2 particles with different sintering temperatures

NiFe2O4 ceramics reinforced with ZrO2 particle was fabricated by conventional high-temperature solid state reaction. Effect of the sintering temperature (1100–1500 °C) on the microstructure and mechanical properties of the ZrO2/NiFe2O4 composite ceramics was investigated in detail. The fracture surfaces of NiFe2O4 composite ceramics were observed by scanning electron microscopy (SEM). Elemental analysis of micro-structural phases was performed using energy dispersive spectroscopy (EDS), attached with SEM. Flexural strength by three-point bending techniques and fracture toughness were measured. It was indicated that when the sintering temperature was above 1400 °C, phase transformation causing crack can directly lead to the strength degradation. The grain size of ZrO2 increases with increasing of the sintering temperature. The samples sintering at 1400 °C had the highest flexural strength of 192 ± 10 MPa and fracture toughness of 3.38 ± 0.05 MPa m1/2 due to densification, phase transformation.

► ZrO2/NiFe2O4 composite ceramics were synthesized by powder metallurgy methods.
► The microstructure was investigated at different sintering temperatures.
► The grain size increases with increasing of the sintering temperature.
► The composite ceramics sintering at 1400°C show superior mechanical properties.
► Main toughening mechanisms are densification, phase transformation toughening.