Effect of BaWO ₄ on the Microwave Dielectric Properties of Ba(Mg _1/3 Ta _2/3 )O ₃ Ceramics

Physical and microwave dielectric properties of complex perovskite Ba(Mg _1/3 Ta _2/3 )O ₃ ceramics have been investigated as a function of the amount of BaWO ₄ in the temperature range from 20° to 80°C at 10.5 GHz. Up to 0.05 mol BaWO ₄ addition, the lattice constant ratio ( c/a ), ordering parameter, apparent density, and unloaded Q all increase, due to the increase in the substitution of Ta ⁵⁺ ions of Ba(Mg _1/3 Ta _2/3 )O ₃ by W ⁶⁺ ions from the melted BaWO ₄ at above 1430°C. With further addition of BaWO _4, the unloaded Q decreases, due to an increase of the BaWO ₄ phase. The temperature coefficient of resonant frequency (TCF) can be controlled by the volume mixture rule of Ba(Mg _1/3 Ta _2/3 )O ₃ and BaWO ₄ . When 0.09 mol BaWO ₄ is added, TCF becomes 0 ppm/°C.