Ceramics-Silikáty 51, (2) 94 - 97 (2007)

Transparent fine-grained MgAl₂O₄ ceramics was prepared from nanometre-sized powder without any sintering additives. Ceramic green bodies were prepared by cold isostatic pressing and then pressureless presintered at temperatures of 1550-1600°C to achieve closed porosity. Presintered samples were subsequently hot isostatically pressed (HIPed) at 1500°C and 200 MPa for 1 hour. The final density as well as the transparency of HIPed samples was affected by presintering densities. The highest final density (~100% t.d.) and highest in-line transmission (60.2% for sample thickness 1.1 mm and λ = 632.8 nm) were obtained for samples presintered to the lowest density value still guaranteeing a structure with closed porosity (~94% t.d.). The HIPed samples had an average grain size of 1 µm and hardness HV = 13.0 GPa.