Optical and Microwave Dielectric Properties of Zn‐Doped MgAl2O4 Transparent Ceramics Fabricated by Spark Plasma Sintering

Abstract

(Mg1−xZnx)Al2O4 transparent ceramics were fabricated by spark plasma sintering technique at 1325°C for 10 min. A small mount of Zn2+ addition to MgAl2O4 ceramics was very effective to the performance improvement, while further increase in Zn‐doped content would give rise to the optical transmittance deterioration. The optical and microwave dielectric properties of MgAl2O4 transparent ceramics were improved by Zn substitution for Mg. The in‐line transmittance of the (Mg1−xZnx)Al2O4 (x = 0.02) ceramics can be as high as 70% at λ = 550 nm and 86.5% at λ = 2000 nm, respectively. The dielectric constant εr of (Mg1−xZnx)Al2O4 just varied from 8.32 to 8.54, however, the Q × f value increased significantly up to a maximal value of 66,000 GHz at x = 0.02. Moreover, the τf of (Mg1−xZnx)Al2O4 transparent ceramics changed from −74 to −65.5 ppm/°C. With the increasing of Zn‐doped content, the average grain size and the porosity increased, which was the primary reason for the change in optical and microwave dielectric properties.