Greener processing of SrFe$_{12}$O$_{19}$ ceramic permanent magnets by two-step sintering

TL;DR

This study introduces a greener two-step sintering process for SrFe$_{12}$O$_{19}$ ceramic magnets, achieving high density and magnetic properties with significantly reduced energy consumption, contributing to sustainable manufacturing.

Contribution

A novel two-step sintering method for Sr-ferrite magnets that reduces energy use while maintaining high density and magnetic performance.

Findings

Achieved 93% relative density in SrFe$_{12}$O$_{19}$ magnets.

Reduced energy consumption by 31% compared to traditional sintering.

Produced magnets with coercivity of 164 kA/m comparable to state-of-the-art.

Abstract

With an annual production amounting to 800 kilotons, ferrite magnets constitute the largest family of permanent magnets in volume, a demand that will only increase as a consequence of the rare-earth crisis. With the global goal of building a climate-resilient future, strategies towards a greener manufacturing of ferrite magnets are of great interest. A new ceramic processing route for obtaining dense Sr-ferrite sintered magnets is presented here. Instead of the usual sintering process employed nowadays in ferrite magnet manufacturing that demands long dwell times, a shorter two-step sintering is designed to densify the ferrite ceramics. As a result of these processes, dense SrFe$_{12}$O$_{19}$ ceramic magnets with properties comparable to state-of-the-art ferrite magnets are obtained. In particular, the SrFe$_{12}$O$_{19}$ magnet containing 0.2% PVA and 0.6% wt SiO$_2$ reaches a coercivity of 164 kA/m along with a 93% relative density. A reduction of 31% in energy consumption is achieved in the thermal treatment with respect to conventional sintering, which could lead to energy savings for the industry of the order of 7.109 kWh per year.