Cold sintering assisted processing of Mn-Zn ferrites

Abstract

Typically, commercial Mn-Zn ferrites are sintered at high temperatures with prolong times. In this work, commercial Fe2O3-rich ferrite powders with the composition of 0.21Mn0.8Zn0.2Fe2O4-0.79Fe2O3 (wt%) are densified by cold sintering at 300 °C with the assistance of organic salts, including MnC2O4·2H2O, FeC2O4·2H2O, and Zn(C2H3O2)2·2H2O. Excessive Fe2O3 enters into spinel structure forming a solid solution through annealing in low pO2 at 1350 °C. The sintering behaviors, microstructures, magnetic properties and impedances are investigated. The dehydration of organic salts provides mediate liquid phase to trigger the dissolution-precipitation process, which assists the densification of ceramics. The grains grow from 0.15 µm to 0.52 µm and 7.67 µm after cold sintering at 300 °C and annealing at 1350 °C, respectively. The initial permeability of cold sintered sample is improved to 11000 with a Curie temperature of 125 °C. This work provides a feasible route for cold sintering assisted processing of commercial soft magnetic ferrites.