The effects of Mg2+ ions on the microwave dielectric properties of BaO-(Nd1-xBix)2O3-4.5TiO2 ceramics

Microwave dielectric properties of BaO-(Nd_1-xBi_x)₂O₃-4.5TiO₂ (x=0∼0.15), hereafter abbreviated as BNBT, ceramics modified with MgO or MgTiO₃ have been investigated to obtain low τ_f materials suited for microwave applications. BNBT ceramics without Mg²⁺ ions showed the dielectric constant of 92 and τ_f of 12∼24 ppm/°C. The addition of MgO into BNBT ceramics up to 0.4 wt.% resulted in a. decrease in the dielectric constant without significant effects on the τ_f. In contrast, the addition of MgTiO₃ into BNBT ceramics reduced the τ_f with an increased dielectric constant. As a result, we obtained BNBT ceramics with ε_r=94, Q×f₀=5, 130 GHz, and τ_f=0.2 ppm/°C, which are promising for commercial applications.