Pressureless sintering of beta-SiAlON ceramic compositions using fluorine and oxide additive system

SiAlONs are silicon aluminium oxynitride ceramic materials with a range of technically important applications, from cutting tools to specialised refractories and the properties of SiAlONs can be tailored for specific purposes. In this study, different beta-SiAlON compositions were prepared using fluoride (MgF2 as fluorine source plus Y2O3) and oxide (MgO plus Y2O3). These compositions were pressureless sintered under nitrogen atmosphere in the range of 1450-1750 degrees C for 0.5-2.5 h for comparison of densification behaviour and mechanical properties. Densities of samples were measured and analyses of result products were carried out using SEM and XRD. The F-doped sintered beta-SiAlON ceramics showed better densities and less pore micrographs especially at lower temperatures compared with the fluorine free samples. Full densifications were achieved for beta-SiAlON ceramics with fluoride addition at 1700 degrees C for 60 min. Consequently, fluorine addition to additive system has a good effect on mechanical properties and densification behaviour. (C) 2011 Elsevier Ltd. All rights reserved.