Variations in Hardness and Grain Size with Density for Fully Stabilized Zirconia Sintered Using Microwave Processing

Abstract

Densification of ceramic materials with microwave energy is being considered as an alternative means to conventional methods. Using microwave processing for sintering ceramics, many researchers have observed higher densities at lower temperatures, as compared with conventional sintering methods. Microwave sintering technology is under investigation for fabricating inert matrix materials that would recycle fuel in proposed Generation IV nuclear reactors. This study examined the variation in hardness with density and the changes in microstructure with processing technique and temperature. The 8 mol% Y 2 O 3 -ZrO 2 samples selected for this study were sintered using a conventional furnace, a multi-mode microwave furnace and a single-mode microwave furnace. Microstructural results on 96% theoretically dense samples showed differences in grain size to processing technique (conventional = 1.58 μm, multi-mode microwave = 1.29 μm, and single-mode microwave = 8.86 μm). Vickers hardness tests were performed on select sample groups representative of each processing method. Similarly, dense samples sintered with a conventional furnace yielded a hardness of 5.37 GPa. Whereas, higher hardness values were observed in similarly dense samples that were processed in a multi-mode microwave (9.28 GPa) and single-mode microwave (7.77 GPa). The results obtained in this study favor microwave sintering at low temperature that could eventually find an application in fabricating inert matrix fuels for next generation reactors.

Effect of Direct Microwave Sintering on Structure and Properties of 8 Mol% Y2O3-ZrO2

“…This behavior implies the completion of the densification stage; the next step in the sintering process would be the onset of grain growth, as seen in Fig. 4 37 . The grain size value for direct microwave sintering was 0.64 μm (at 1100°C) and, with the increase in temperature, this value increased to 8.86 μm (at 1500°C).…”

“…4. 37 The grain size value for direct microwave sintering was 0.64 mm (at 11001C) and, with the increase in temperature, this value increased to 8.86 mm (at 15001C). For the cases, of conventional and microwave hybrid sintering, an appreciable grain structure could only be seen at temperatures 412001C.…”