Effect of glass addition on microwave properties of BaO•La2O3•4.7TiO2

The effects of the addition of glass to the microwave properties of BaO . La2O3. 4.7TiO(2) ceramics were investigated. Three commercial glasses. PbO-B2O3-SiO2 (GA9), ZnO-B2O3-SiO2 (GP032) and PbO-Ba2O3 (LS3081), were investigated in this study. The ceramics without glass addition and sintered at 1300 degrees C gave the relative dielectric constant epsilon(r) = 92, quality factor Q = 1653 and temperature coefficient of resonant frequency tau(f) = 40.3 ppm/degrees C at 3.0 GHz. With 20 wt% GA9 addition. highly dense samples (void fraction were less than or equal to 2.5 vol%) were obtained at T, greater than or equal to 900 degrees C and their microwave properties were: epsilon(r) greater than or equal to 64, Q greater than or equal to 1037 and tau(f) less than or equal to 15.3 ppm/degrees C at 3.0 GHz. The high sintering temperature increased epsilon(r) and Q values but decreased the value of tau(f). The densification of specimens was found to play an important role in improving the dielectric constant. Heterogeneous interfaces and the dissolution of trace amounts of ceramics in glass increased the dielectric loss significantly; also, the former increased tau(f) whereas the latter decreased it.