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Densification of Sr-Mg doped SiAlONs with GPS and SPS

: Kurama, S.; Herrmann, M.


Mandal, H. ; European Ceramic Society:
Nitrides and oxynitrides III. Proceedings of the 5th International Symposium on Nitrides 2006 : Anadolu University, Eskisehir, Turkey, April 3 - 5, 2006; ECERS topical meeting
Stafa-Zürich: Trans Tech Publications, 2007 (Materials Science Forum 554)
ISBN: 0-87849-439-1
ISBN: 978-0-87849-439-2
International Symposium on Nitrides <5, 2006, Eskisehir, Turkey>
Fraunhofer IKTS ()
SiAlON; Fremdatomzusatz; Magnesiumion; Strontiumion; Verdichtung; Gasdrucksintern; Funkenentladungsplasmasintern; Sintertemperatur; Phasenumwandlung; Mikrostruktur; mechanische Eigenschaft

At temperature above 1200 deg C, the thermal stability of alpha-SiAlON phases has been debated since 1992; however, it has been discussed if any alpha-SiAlON phase can be formed in Ce, La, Eu and Sr-doped SiAlON systems. In previous studies it was shown that the use of Mg-Ce and Mg-Sr elements as dopants SiAlON compositions, in which all elements just have very low or no stability in the alpha-SiAlON structure, would promote the stability of Mg-Ce elements in the alpha-SiAlON phase. However, in Mg-Sr systems, it was obtained that Mg(2+) is predominantly incorporated in alpha-SiAlON structure whereas Sr(2+) mainly remains in the grain boundaries. In this study, by applying spark plasma sintering (SPS) (at 1400-1700 deg C) and post-sintering thermal heat treatment (at 1500 deg C for 5 hrs and 1700 deg C for 2hrs) Mg or Mg-Sr doped SiAlON (50:50 mole ratios) ceramics were prepared. The results were compared with GPS (gas pressure sintering) sintered samples data. The effect of sintering temperature on densification process, phase transformation, microstructure and mechanical properties of samples were investigated. The results showed that by using SPS, Sr-Mg doped samples can be sintered at lower temperature (at 1600 deg C) than at GPS (at 1800 deg C) and it has no Sr-doped grain boundary phases.