Multivariate Statistical Analysis of Spectrum Lines From Si3N4 Grain Boundaries

Abstract

It is well known that the high-temperature properties of polycrystalline Si3N4 ceramics are strongly influenced by the nanometer-scale glassy phase at the grain boundaries. We have recently analyzed the variation of the near-edge fine structure (ELNES) of the Si-L2,3 edges using a combination of TEM spectrum-line acquisition with an imaging filter and multivariate statistical analysis.The glassy phase at the Si3N4 grain boundaries is easily damaged by the the fine probes usually used in scanning transmission electron microscopy to acquire ELNES data. Thus an alternative method using a Gatan imaging filter (GIF), called TEM spectrum-line analysis, was used. In this mode, energy-loss spectra are dispersed along one axis of the CCD detector, while the orthogonal axis displays the spatial variation across the interface. In this mode, a slotted washer is used as the GIF entrance aperture, with its minor axis parallel to the energy-dispersion direction of the spectrometer.