Structure and microwave dielectric properties of Ba3(VO4)2–Zn2−xSiO4−x ceramic composites

Highlights: ► New Ba{sub 3}(VO{sub 4}){sub 2}–Zn{sub 1.87}SiO{sub 3.87} microwave dielectric composite ceramic was reported. ► The single-phase willemite was obtained by controlling of ZnO deficiency. ► The composite with 40 wt% Zn{sub 1.87}SiO{sub 3.87} exhibited excellent τ{sub f} value of 0.4 ppm/°C. - Abstract: Microwave dielectric ceramic composites with compositions of (1 − y)Ba{sub 3}(VO{sub 4}){sub 2}–yZn{sub 2−x}SiO{sub 4−x} (y = 0.4–0.6, x = 0.13) have been prepared by firing mixtures of Ba{sub 3}(VO{sub 4}){sub 2} and Zn{sub 1.87}SiO{sub 3.87}. The X-ray diffraction (XRD) analysis revealed that Zn{sub 2}SiO{sub 4} with a willemite phase can be obtained by appropriately controlling the ZnO deficiency. The starting Zn{sub 1.87}SiO{sub 3.87} powder should be thus composed of the ZnSiO{sub 4} crystal phase and redundant SiO{sub 2} amorphous phase at room temperature. The scanning electron microscopy studies demonstrated the coexistence of Zn{sub 2}SiO{sub 4} and Ba{sub 3}(VO{sub 4}){sub 2} phases in the sintered bodies, as further confirmed by the XRD and Raman results. The near-zero temperature coefficients of the resonant frequency (τ{sub f}) could be achieved by adjusting the relative content of the two phases owing to their opposite τ{sub f} values. The existence of a slight amount of secondary phases, element interdiffusionmore » and non-stoichiometry such as Zn deficiency altogether made the predicted property values deviate from the experimentally measured ones. The composite ceramics with 40 wt% Zn{sub 1.87}SiO{sub 3.87} sintered at 1100 °C exhibited desirable microwave dielectric properties of the quality factor Q × f ∼ 23,000 GHz, dielectric constant e{sub r} ∼ 9.3, and τ{sub f} ∼ 0.4 ppm/°C.« less