Microwave Dielectric Properties of Ba_4.2(Sm_0.8Nd_0.17Bi_0.03)_9.2Ti₁₈O₅₄ Solid Solution with TiO₂ Added

The effects of TiO₂ addition on the microwave dielectric properties of Ba_6-3x(Sm_1-y-zNd_yBi_z)_8+2xTi₁₈O₅₄ (BSNBT) ceramics, with x=0.6, y=0.17, and z=0.03, have been investigated. The microstructure of BSNBT doped with TiO₂ was analyzed using X-ray diffraction (XRD) analysis, electron probe microanalysis (EPMA) and field-emission scanning electron microscopy (FE-SEM). XRD and EPMA analysis reveals the existence of second phases. The addition of small amounts of TiO₂ (≤1.0 wt %) increased Q·f markedly and improved TC f without any influence on dielectric constant (ε_r). However, the addition of excess TiO₂ reduced the bulk density and dielectric properties of the materials. BSNBT doped with 0.5 wt % TiO₂ exhibited excellent dielectric properties with ε_r=80.5, Q·f=9009 GHz and TC f=6.5 ppm/°C when sintered at 1340 °C for 2 h. The reasons for the nonlinear behavior of TC f are also provided.