Modification of MgAl ₂ O ₄ Microwave Dielectric Ceramics by Zn Substitution

MgAl 2 O 4 microwave dielectric ceramics were modified by Zn substitution for Mg, and their dielectric characteristics were evaluated, along with their structures. Dense (Mg 1− x Zn x )Al 2 O 4 ceramics were obtained by sintering at 1550°–1650°C in air for 3 h, and the (Mg 1− x Zn x )Al 2 O 4 solid solution was determined in the entire composition range. With Zn substitution for Mg, the dielectric constant ɛ of MgAl 2 O 4 just varied from 7.90 to 8.56, while the Q × f value had significantly improved up to a maximal value of 106 000 GHz at x =1.0. Moreover, the τ f of MgAl 2 O 4 ceramics had declined from −73 to −63 ppm/°C.