Highly dense spinel ceramics with completely suppressed grain growth prepared via SPS with NaF as a sintering additive

For the preparation of transparent spinel ceramics it is common practice to use LiF as a sintering additive to achieve transparency. However, it is well known that in this case the grain size exhibits a significant increase compared to pure spinel ceramics, which can lead to a deterioration in mechanical properties. The findings of this paper indicate that when NaF is used as a sintering additive for the preparation of spinel ceramics via spark plasma sintering (SPS) translucent materials with a high level of densification can be obtained without observable grain growth. It is shown that the grain size after SPS at 1500 degrees C with 1 h dwell is essentially the same as the primary particle size of the spinel powder, whereas pure spinel ceramics prepared via SPS under the same conditions exhibit grain growth by approximately a factor 5.