Crystal Structure and Ferroelectric Evidence of BaZnSi₃ O₈ , a Low-Permittivity Microwave Dielectric Ceramic

BaZnSi₃ O₈ ceramic was prepared by the conventional solid-state method and sintered at 1100 °C. XRD and synchrotron Rietveld refinement analyses revealed the BaZnSi₃ O₈ ceramic presented a monoclinic structure with a space group of P2₁ /a (No.14), which is reported for the first time. The BaZnSi₃ O₈ ceramic presented a weak ferroelectricity, which was confirmed by the P-E loop and the 90° nanoscale ferroelectric domain. Although ϵ_r -T displayed two ϵ_r abnormal peaks at 400 °C and 460 °C, the Curie temperature (T_c ) was located at 460 °C according to the dielectric loss and Curie-Weiss law. Moreover, the BaZnSi₃ O₈ ceramic exhibited optimized microwave dielectric properties with ϵ_r =6.55, Q×f=52400 GHz, and τ_f =-24.5 ppm/°C. Hence, the BaZnSi₃ O₈ ceramic in the ternary BaO-ZnO-SiO₂ system possessed both weak ferroelectricity and microwave dielectric properties. These results are expected to break the technical barrier of ferroelectric phase shifter applications in microwave and even millimeter-wave frequency bands.