Synthesis and microwave dielectric properties of 2ZnO⋠3B2O3-doped ZnAl2O4 low-permittivity ceramics

2ZnO⋅3B2O3-doped ZnAl2O4 ceramics were synthesized via solid-state method. Influence of different 2ZnO⋅3B2O3 additions on the microstructure, sintering behavior and microwave dielectric properties has been investigated. The results showed that zinc borate could effectively improve the densification and expand the sintering temperature range. Microwave dielectric properties of 2ZnO⋅3B2O3-doped ZnAl2O4 ceramics were exhibited as follow: εr = 8.32, Q × f = 93,600 GHz (at 14.0 GHz) and τf = −68.5 ppm/°C. Spinel-structured zinc borate-doped ZnAl2O4 ceramics possessed comparatively low sintering temperatures, wide temperature regions (about 100 °C), simultaneously, high Q × f and stable τf values. These outstanding performance make them promising candidate materials for millimeter-wave devices at high frequency.