B6O is a possible candidate of superhard materials with a hardness of 45 GPa measured on single crystals. Up to now, densification of these materials was only possible at high pressure. However, recently it was found that Al2O3 can be utilized as an effective sintering additive, similar to the addition of Y2O3/Al2O3 that was used in this work. The densification behavior of the material as a function of applied pressure, its microstructure evolution, and the resulting mechanical properties were investigated. A strong dependence of the densification with increasing pressure was found. The material revealed characteristic triple junctions filled with amorphous residue composed of B2O3, Al2O3, and Y2O3, while no amorphous grain-boundary films were observed along internal interfaces. Mechanical testing revealed on average a hardness of 33 GPa, a fracture toughness of 4 MPa·m1/2, and a strength value of 520 MPa.
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Document Type: Research Article
Fraunhofer Institute of Ceramic Technologies and Systems, D-01277 Dresden, Winterbergstr 28, Germany
Institute for Applied Geosciences, Technische Universität Darmstadt, Schnittspahnstr 9, D-64287 Darmstadt, Germany
School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg, South Africa
Publication date: October 1, 2009