Oxide and interface characteristics of oxidized silicon oxynitride ceramics - an investigation by electron microscopy

Hot-isostatically pressed silicon oxynitride (Si2N2O) ceramics free from si ntering aids were oxidized in 1 atm dry oxygen at 1100 a nd 1300 degrees C. The structural a nd chem ica I characteristics of the oxide and the nature of the oxide-Si2N2O interface were determined using cross-sectional transm ission electron microscopy in conjunction with small-probe energy dispersiv e X-ray ana lysis and selected-a rea electron diffraction. Oxidation of Si2 N2O resulted in the formation of amorphous SiO2. The oxide-Si2N2O interface was chemically abrupt. The interface was very flat when parallel to low-in dex, high atomic density Si2N2O crystal planes but became notably undulated if oriented to high index, low atomic density planes. About 6 vol % residu al SiO2 phase was present in the bulk of the Si2N2O ceramics. Current resul ts have provided an important baseline for the understanding of the oxidati on behaviour of Si2N2O (C) 1998 Kluwer Academic Publishers.