Microwave dielectric properties of AWO4 (AÂ =Â Ca, Ba, Sr) ceramics synthesized via high energy ball milling method

The AWO4 (A = Ca, Sr, Ba) compounds with scheelite structure were synthesized by high energy ball milling for 30 min and the average particle size was reduced to about 120 nm after milling 30 h. AWO4 ceramics were well sintered at relatively low temperatures of 900-1000 °C, 200-400 °C lower than those required by a conventional solid state reaction technique. The samples of CaWO4, SrWO4, and BaWO4 ceramics have dense microstructures and excellent microwave dielectric properties, ɛr = 10.7, 8.6, 8.4; Q × f = 62,100 GHz, 57,500 GHz, 58,800 GHz; and τf = −48 ppm/°C, −52 ppm/°C, −64 ppm/°C, respectively.