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

Journal Article · Tue Jul 12 04:00:00 EDT 2005 · Materials Research Bulletin

DOI:https://doi.org/10.1016/j.materresbull.2005.03.017· OSTI ID:20889794

Santos, C ^[1]; Strecker, K ^[1]; Suzuki, P A ^[1]; Kycia, S ^[2]; Silva, O M.M. ^[3]; Silva, C R.M. ^[3]

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1. Faculdade de Engenharia Quimica de Lorena (FAENQUIL), Departamento de Engenharia de Materiais (DEMAR), Polo Urbo-industrial, gleba AI-6, s/n, CEP 12600-970, Caixa Postal 116, Lorena, SP (Brazil)
2. Laboratorio Nacional de Luz Sincrotron (LNLS), CEP 13084-971, Caixa Postal 6192, Campinas, SP (Brazil)
3. Centro Tecnico Aeroespacial - DiviSao de Materiais CTA-IAE-AMR, Pca. Marechal do Ar Eduardo Gomes, 50, CEP 12228-904, Sao Jose dos Campos, SP (Brazil)

{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.

• OSTI ID: 20889794
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 7 Vol. 40; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM NITRIDES
ALUMINIUM OXIDES
ASPECT RATIO
CERAMICS
CRYSTAL STRUCTURE
FRACTURE PROPERTIES
GRAIN SIZE
HARDNESS
PRESSURE RANGE GIGA PA
RARE EARTHS
SILICON NITRIDES
SINTERING
SOLID SOLUTIONS
STABILIZATION
SYNCHROTRONS
X-RAY DIFFRACTION
YTTRIUM OXIDES