Crystal structure and ferroelectric evidences of BaZnSi3O8 low-permittivity microwave dielectric ceramic.

BaZnSi 3 O 8 ceramic was prepared via the conventional solid-state method and sintered at 1100 °C. XRD and synchrotron Rietveld refinement analyses revealed the BaZnSi 3 O 8 ceramic presented monoclinic structure with a space group of P 2 1 /a (No.14), which was reported for the first time. The BaZnSi 3 O 8 ceramic presented a weak ferroelectricity, which was confirmed by the P-E loop and the 90° nanoscale ferroelectric domain. Although e r - T displayed two e 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 BaZnSi 3 O 8 ceramic exhibited optimised microwave dielectric properties with e r = 6.55, Q × f = 52400 GHz, and τ f = -24.5 ppm/°C. Hence, the BaZnSi 3 O 8 ceramic in the ternary BaO-ZnO-SiO 2 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.