Different pressures of 80 and 90 MPa were applied to produce Y 2 O 3 ceramics by spark plasma sintering in this work. Effects of pressure were investigated on densification, microstructure, infrared (IR) transmission and mechanical properties. It was found that applying higher pressure led to finer microstructure and consequently higher hardness and fracture toughness. An IR-transparent Y 2 O 3 ceramic with 60% transmission at wavelength of 5 µm was obtained by sintering at 1300°C under uniaxial pressure of 90 MPa. This sample had an average grain size of 0.76 µm and hardness and fracture toughness of 9.37 GPa and 1.60 MPa.m 1/2 , respectively.

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In the present study, zinc selenide powder was successfully sintered using spark plasma sintering. The effect of spark plasma sintering temperature and pressure on the densification, microstructure and hardness were investigated. Relative density, microstructure, hardness and crystallographic properties of specimens were evaluated by means of the Archimedes method, optical microscopy/scanning electron microscopy, micro-Vickers and X-ray diffraction, respectively. The results indicated that temperature and pressure were the most effective parameters affecting the process. The maximum relative density (99.3%) and hardness (163 kg mm−2) were obtained using conditions of 1100°C for 5 min under 70 MPa. The crystallographic orientation (twinning) observed by optical microscopy was confirmed by X-ray diffraction results.