Low temperature in-situ reaction sintering of zircon: Alumina composites trough spark plasma sintering

Pure Zircon and Zircon: Alumina (ZrSiO4: ?-Al2O3) composite powders were subjected to densification studies employing spark plasma sintering (SPS). Physico chemical and microstructural properties of the samples were evaluated and compared with that of conventionally sintered (CRH-Constant Ramp and Hold) compacts. Density measurements and microstructural evaluation revealed a low temperature densification of Zircon: Alumina at temperatures as low as 1300?C by SPS. Increase of temperature to 1350?C had shown negligible changes in density and on further heating the sample melts at 1400?C as a result of excessive formation of liquid phase. However, pure zircon could not be densified in the absence of alumina under SPS conditions. It is evident that addition of alumina enhances partial low temperature decomposition of zircon under the influence of plasma generated during SPS. Mullite formed as a result of this insitu reaction between alumina and silica acts as a bonding phase as revealed by the X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Electron disperse scanning (EDS) analysis.