Optical and microwave dielectric properties of transparent MgAl_2O_4 ceramics fabricated by Spark Plasma Sintering

摘要

Transparent polycrystalline MgAl_2O_4 ceramics were fabricated through homemade nanosized MgAl_2O_4 powders by using spark plasma sintering (SPS) technique at a temperature range from 1275°C to 1400 °C. The samples fabricated at optimal sintering processes have cubic spinel structure with an average grain size of 345 nm. The in-line transmittance of the sintered ceramics can be as high as 70% at 550 nm and 82% at 2000 nm, respectively. As the sintering temperature increases, Qxf andτ f values increase to maximum and then decrease respectively, while ε_r value is almost independent of the sintering temperature and remains between 8.3 and 8.43. The optimal microwave dielectric properties(ε_r = 8.38, Qxf = 54000 GHz and τ_f= -74 ppm/°C) were achieved for transparent MgAl_2O_4 ceramics produced by spark plasma sintering at 1325°C for 20 min.