Grain growth of MgAl2O4 ceramics with LiF and NaF addition

Abstract

The effects of LiF and NaF sintering additives on the grain growth of spinel ceramics prepared via spark plasma sintering (SPS) are investigated and compared for dwell times in the range 0–120 ​min. Absence of sintering additives resulted in abnormal grain growth, whereas LiF addition allowed continuous (normal) grain growth, although with final grain size larger by a factor 12 after 120 ​min dwell time. By contrast, NaF is the other extreme, its addition results in very little grain growth (by a factor of only 1.2 after 120 ​min dwell time), thus preserving a grain size very close to nanometric. Occasionally, large highly faceted grains were observed, indicating inadequate homogenization in the case of spinel ceramics with NaF addition. Nevertheless, it seems that addition of NaF is suitable for the preparation of dense nanocrystalline spinel ceramics without any extreme conditions applied (high pressure).

Keywords

• Spark plasma sintering (SPS)
• Sintering additives
• Magnesium aluminate spinel
• Grain growth
• Magnesia alumina spinel