The role of carbon presence on the strontium hexaferrite phase decomposition during pressureless spark plasma sintering (pSPS)

Abstract

The phase composition and microstructure of Sr-hexaferrite (SFO) ceramics govern the hard magnetic properties. Here, pressureless spark plasma sintering (pSPS) technique was employed for the rapid consolidation (500 °C/min) of SFO in a radiating graphite crucible under vacuum and, thus, reductive conditions. A numerical model depicting the temperature profile within the heating crucible was constructed to understand the temperature evolution within the samples. The combination pSPS sintering environment (graphite heating crucible under vacuum) promoted phase decomposition to Sr-enriched and depleted phases of various morphological variations, leading to reduction of hard magnetic properties. Notably, certain newly formed phases exhibited lower melting points, inducing a shift in the sintering mechanism from solid-state sintering to a partial liquid-phase sintering mechanism.