Stabilization of {alpha}-SiAlONs using a rare-earth mixed oxide (RE{sub 2}O{sub 3}) as sintering additive

{alpha}-SiAlONs are commonly produced by liquid phase sintering of Si{sub 3}N{sub 4} with AlN and Y{sub 2}O{sub 3} as additives. The formation of the {alpha}-SiAlONs using a mixed oxide (RE{sub 2}O{sub 3}), containing yttria and rare-earth oxides, as an alternative additive was investigated. Dense {...

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Published inMaterials research bulletin Vol. 40; no. 7
Main Authors Santos, C., Strecker, K., Suzuki, P.A., Kycia, S., Silva, O.M.M., Silva, C.R.M.
Format Journal Article
LanguageEnglish
Published United States 12.07.2005
Subjects
ALUMINIUM NITRIDES
ALUMINIUM OXIDES
ASPECT RATIO
CERAMICS
CRYSTAL STRUCTURE
FRACTURE PROPERTIES
GRAIN SIZE
HARDNESS
MATERIALS SCIENCE
PRESSURE RANGE GIGA PA
RARE EARTHS
SILICON NITRIDES
SINTERING
SOLID SOLUTIONS
STABILIZATION
SYNCHROTRONS
X-RAY DIFFRACTION
YTTRIUM OXIDES
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Summary:{alpha}-SiAlONs are commonly produced by liquid phase sintering of Si{sub 3}N{sub 4} with AlN and Y{sub 2}O{sub 3} as additives. The formation of the {alpha}-SiAlONs using a mixed oxide (RE{sub 2}O{sub 3}), containing yttria and rare-earth oxides, as an alternative additive was investigated. Dense {alpha}-SiAlONs were obtained by gas-pressure sintering, starting from {alpha}-Si{sub 3}N{sub 4} and AlN-Y{sub 2}O{sub 3} or AlN-RE{sub 2}O{sub 3} as additives. The mixed oxide powder RE{sub 2}O{sub 3} was characterized by means of high-resolution synchrotron X-ray diffraction and compared to Y{sub 2}O{sub 3}. The X-ray diffraction analysis of the mixed oxide shows a pattern indicating a true solid solution formation. The Rietveld refinement of the crystal structure of the sintered {alpha}-SiAlON using AlN-RE{sub 2}O{sub 3} as additive revealed a similar crystal structure to the {alpha}-SiAlON using AlN-RE{sub 2}O{sub 3} as additive. The comparison of the microstructures of the both {alpha}-SiAlONs produced using pure Y{sub 2}O{sub 3} or RE{sub 2}O{sub 3}, revealed similar grain sizes of about 4.5 {mu}m with aspect ratios of about 5. Both materials show also similar mechanical properties, with hardness of 18.5 GPa and fracture toughness of 5 MPa m{sup 1/2}. It could be, thus, demonstrated that pure Y{sub 2}O{sub 3} can be substituted by the rare-earth solid solution, RE{sub 2}O{sub 3}, in the formation of {alpha}-SiAlONs, presenting similar microstructural and mechanical properties.
ISSN:0025-5408
1873-4227
DOI:10.1016/j.materresbull.2005.03.017