The synthesis and microwave dielectric properties of Mg3B2O6 and Mg2B2O5 ceramics

Single-phase Mg3B2O6 and Mg2B2O5 ceramics were synthesized and then structurally and dielectrically characterized. The highest Qxf value of 230,900 GHz was obtained for a Mg3B2O6 ceramic with a density of 97% and 1000-μm grains. Considerably lower Qxf values (10,000–32,000 GHz) were determined for the Mg2B2O5 ceramic. Mg3B2O6 and Mg2B2O5 exhibited permittivities (ɛ) of 7.2 and 6.2–7.0, respectively. Both ceramics showed negative temperature coefficients of resonant frequency (τf) of −18 to −45 ppm/°C.