Effect of MnO2 Addition on Early‐Stage Sintering Behavior and Properties of NiFe2O4 Ceramics

The samples with small amounts of MnO2 (0, 0.5, 1.0, 2.5 wt%, respectively) were prepared via ball-milling process and two-step sintering process from commercial powders (i.e. Fe2O3, NiO and MnO2). Microstructure features, phase transformation, the early-stage sintering behavior and mechanical properties of Mn-doped NiFe2O4 samples have been investigated. Results indicate that the reduction of MnO2 into Mn2O3 and following the reduction of Mn2O3 into MnO existed in sintering process. No new phases are detected in the matrix, the crystalline structures of ceramic matrix are still NiFe2O4 spinel structure. MnO2 addition can promote the sintering process. The temperature for 1 wt% MnO2-doped samples to reach the maximum shrinkage rate is 59 °C lower than that of un-doped samples.