Formation of in situ Reinforced Microstructures in α-sialon Ceramics: Part II. In the Presence of a Liquid Phase.
2002 (English)In: Journal of Materials Research, ISSN 0884-2914, Vol. 17, no 5, 1136-1142 p.Article in journal (Refereed) Published
In situ reinforced microstructures with well-dispersed elongated grains, up to 10 μm in length, embedded in matrices consisting of submicron equiaxed grains, were developed by hot pressing Y-, Yb-, and (Y + Yb)-doped a-sialon ceramics containing approximately 3 vol% extra liquid phase at a comparatively low sintering temperature, 1800 °C. The liquid phase, thermodynamically compatible with a-sialon, was introduced by raising the oxygen content of an already oxygen-rich α-sialon composition, e.g., by increasing the O/N ratio in RExSi12-(3x+n) Al3x+nOnN16−n. Two different α–Si3N4 precursor powders, one fine-grained and one coarse, and one coarse β–Si3N4 powder were used, and the influence of particle size and crystalline modification of the precursor Si3N4 powder on the formation of elongated a-sialon grains was investigated. The formation of elongated α-sialon grains was promoted by introducing an extra liquid phase and by using a fine-grained α–Si3N4 powder, whereas the coarse β–Si3N4 powder did not yield any elongated grains at all. The obtained in situ reinforced α-sialon ceramics were both hard and tough, with a Vickers hardness and a fracture toughness of 21 GPa and approximately 5 MPa m1/2, respectively.
Place, publisher, year, edition, pages
2002. Vol. 17, no 5, 1136-1142 p.
IdentifiersURN: urn:nbn:se:su:diva-22948DOI: 10.1557/JMR.2002.0168OAI: oai:DiVA.org:su-22948DiVA: diva2:189793