It is argued that the sintering and densification of Si3N4 based ceramics, using transition metal or rare earth metal oxide additives, can be described as an electronic mechanism involving a transfer of electrons into the Si3N4–SiO2 valence band: this is consistent with a recently proposed model of bonding at metal/ceramic interfaces. Transition metal/rare earth metal oxides with a ‘metallic’ character tend to aid densification during sintering of Si3N4–β sialon whereas insulator type metal oxides are less effective densifiers.
MST/1855
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