High-Q microwave dielectrics in the (Mg1−xZnx)4Ta2O9 ceramics

(Mg1−xZnx)4Ta2O9 (x = 0.02-0.08) ceramics were prepared using a solid-state reaction process, and their dielectric properties were characterized at microwave frequency. The formation of solid solutions (Mg1−xZnx)4Ta2O9 were confirmed by the X-ray diffraction patterns. Molecular volumes (Vm) and ionic polarizabilities (αobs) of the specimens were also calculated, which varied linearly from Vm = 323.99 Å, αobs = 61.321 Å3 for (Mg0.98Zn0.02)4Ta2O9 to Vm = 324.24 Å, αobs = 61.510 Å3 for (Mg0.92Zn0.08)4Ta2O9. The dielectric properties are strongly dependent on the compositions, the densifications and the microstructures of the specimens. The composition (Mg0.95Zn0.05)4Ta2O9 has good microwave dielectric properties with an ɛr of 12.67, an extremely high Q × f of 385,000 GHz, and a τf of −61.9 ppm/°C. Addition of B2O3 can lower the sintering temperatures of specimens; whereas it also degrades the Q × f values.