Influence of Bi substitution on microwave dielectric properties of BaO-La2O3-Sm2O3-TiO2 ceramics

The influences of Bi substitution on microwave dielectric properties of Ba-4(La0.5Sm0.5)(9.33)Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba-4(La(0.5-z)Sm0.5Bi (z) )(9.33)Ti18O54, z = 0.0-0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents using open-ended coaxial probe method in the frequency range 0.3-3.0 GHz at room temperature. Dielectric constant varies from 83 to 88 and loss tangent from 2.1 x 10(-3) to 5.5 x 10(-3) at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to -8.4 ppm/A(0)C as Bi contents increases from z = 0.00-0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas loss tangent is adversely affected with increase in Bi substitution.