Abstract
The α-β transformation of Si3N4 during liquid-phase sintering appears to be controlled by the growth of the β-Si3N4 grains in the direction perpendicular to thec-axis in the case of MgO additive. The diffusion through the liquid is the rate-controlling step in the case of the Y4Al5O12 additive. The density of the sintered body at the solid skeleton stage was influenced by the change in the α-β transformation rate and/or by a change of the transformation mechanism. The indirect proportionality between the β-phase content in the starting powder and the density at the solid skeleton stage was found. The microstructure of the sintered body is influenced by both the β-phase content in the starting powder and the chemical composition of the additive. Fine, uniform microstructure with a high aspect ratio of β-grains is obtained, when the β-phase content in the starting powder is as small as possible and when the α-β transformation is controlled by grain growth.
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Prokešova, M., Pánek, Z. Phase transformation and densification during pressureless sintering of Si3N4 with MgO and Y3Al5O12 additives. J Mater Sci 25, 3709–3713 (1990). https://doi.org/10.1007/BF00575409
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DOI: https://doi.org/10.1007/BF00575409