Microstructure and phase composition of steatite ceramics sintered by traditional and spark plasma sintering
The influence of the sintering method on the mineral phase transformations and development of the crystalline microstructure of steatite ceramics was investigated. The steatite samples were fabricated from talc and bentonite as low-cost raw materials. Feldspar and barium carbonate, as fluxing agents, were altered in the steatite composition. Dilatometric analysis was applied in the monitoring of the dimensional changes and thereby densification of steatite during the traditional sintering (TS) procedure up to 1200 °C. Spark plasma sintering (SPS) method was used under the following sintering conditions: 100 °C/min heating rate, uniaxial pressure of 50 MPa; sintering temperature 800 °C/1 min or 1000 °C/2 min. Crystallinity changes and mineral phase transition during sintering were observed by X-ray diffraction technique. Microstructural visualization of the samples and the spatial arrangements of individual chemical elements were achieved via scanning electron microscopy equipped with the EDS mapping. It was found that SPS sintering facilitated all microstructural changes during high temperature treatment and shifted them to lower temperatures. SPS treatment conducted at 1000 °C resulted in maximum densification of the steatite powder compacts and the formation stabilized protoenstatite structure.
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