Effects of B2O3 addition on the microwave dielectric properties of Ba2Ti9O20 ceramics

Microwave characteristics of Ba2Ti9O20 ceramics added with different amounts of B2O3 and sintered at high temperatures ranging from 900 to 960degreesC for 2 h are investigated. It is found that the firing temperature required to densify the Ba2Ti9O20 ceramics is lowered by increasing the B2O3 content. The density and dielectric constants of the B2O3-added ceramics also increase with B2O3 addition. The results of X-ray diffraction (XRD) indicate the presence of five crystalline phases, Ba2Ti9O20, BaZr(BO3)(2), BaZrO3, BaTi4O9, and Zn-3(BO3)(2), in the sintered ceramics, depending upon the amount of B2O3 added. Optimum dielectric properties, i.e., Q = 1477 (Q x f = 10784), epsilon(r) = 28.3, and tau(f) = -8.2, are obtained for the Ba2Ti9O20 ceramics with 3 wt% B2O3 addition and sintering in air at 940degreesC for 2 h.