Improved mechanical properties of dense β-Si3N4 ceramics fabricated by spark plasma sintering with Al2O3-YSZ additives
2018
In this work the influence of sintering conditions on structure and
mechanical properties of Si3N4 ceramics was investigated. Nearly full dense
β-Si3N4 ceramics with excellent mechanical properties and interlock
microstructure of elongated grains was fabricated using Al2O3 and
yttria-stabilized zirconia (YSZ with 3mol% Y2O3) as sintering additives by
spark plasma sintering (SPS) at relatively low temperature of 1600°C for
15min. X-ray diffraction analysis shows that the SPSed sample is pure
β-Si3N4 phase without any secondary crystalline phase. The elements Al, Zr,
Y and O of the additive can diffuse into Si3N4 lattice forming β-Si3N4-
based solid solution. The residual additive formed an amorphous phase at the
β-Si3N4 grain boundaries. The β-Si3N4 ceramics obtained by SPS using 6.0wt.%
Al2O3 and 6.0 wt.% YSZ as additives shows interlock elongated β-Si3N4 grains
of 500 nm in width and 3000 nm in length, high density of 3.29 g/cm3,
Vickers hardness of 16.15GPa and high fracture toughness KIC of 6.75MPam1/2.
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