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J. Neumann-Zdralek
Elektronenmikroskopische Untersuchungen zur Fresnoitbildung in Bariumtitanatkeramik
Dissertation (1999),

The well known compound BaTiO3 is widely used for capacitors, sensors, PTC thermistors and other devices. The properties of the ceramic can be controlled through different sintering regimes and/or by using secondary phases. If SiC or SiO2 is used as an additive, fresnoite (Ba2TiSi2O8) form. This phase influences the grain growth essentially. The main interest was directed to comparative studies of microwave and conventional sintered bodies with respect to their microstructure development. It was essential contents of work to examine the formation of fresnoite as a solid state reaction at temperatures below liquid phase formation. For this purpose, test charges (with SiC or SiO2) were annealed at the temperature range from 600 to 1100°C. The temperature was adjusted both by conventional heating and by microwave heating. In the case of microwave heating, SiC acts as an internal suszeptor, wich improves the heating-up process of the body.
The structural analysis of the ceramics was carried out by electron microscopy (Philips XL 30 ESEM FEG) and scanning transmission electron microscopy (VG HB501UX). The growing of fresnoite in dependance of the sintering temperature was observed by EELS using a fingerprint-technique.

Keywords: Electron microscopy, STEM, ESEM, EDX, EELS, barium titanate, ceramic, microwave sintering, solid state reaction

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