Low permittivity MgO–xB2O3–yBaCu(B2O5) microwave dielectric ceramics for low temperature co-fired ceramics technology

MgO– x B 2 O 3 – y BaCu(B 2 O 5 ) ceramics were prepared by a solid-state reaction method. The phase composition and microwave dielectric properties of ceramics were studied. The MgO-rich ceramics ( x = 1/4, 1/3 and 1/2) contain MgO and Mg 3 B 2 O 6 . But the B 2 O 3 -rich ceramics ( x = 1, 2 and 3) contain B 2 O 3 , MgB 2 O 4 and Mg 2 B 2 O 5 . The MgO– x B 2 O 3 ( x = 1/4, 1/3, 1/2, 1, 2 and 3) ceramics show high Q × f of 41,754–105,852 GHz, low ε r of 4.24 ~ 7.68 and negative τ f values of − 56 to − 30 ppm °C −1 with tuning the x values. The BaCu(B 2 O 5 ) (BCB) was used to reduce the sintering temperature of MgO–2B 2 O 3 ceramic. The MgO–2B 2 O 3 -4 wt% BCB ceramic sintered at 925 °C exhibits good microwave dielectric properties with high Q × f of 30,589 GHz, low ε r of 4.8 and negative τ f value of − 40 ppm °C −1 . Importantly, MgO–2B 2 O 3 -4 wt% BCB ceramic has a good chemical compatibility with Ag, which illustrates that it is a candidate material for low temperature co-fired ceramic devices.