Microwave dielectric properties and microstructures of (Ba1-xPbx)O•La2O3•4.7TiO2 ceramics

The evolution and correlation of microwave dielectric properties and microstructures were investigated systematically for ceramics composed of (Ba1-xPbx)O . La2O3 . 4.7TiO(2) (0 less than or equal to x less than or equal to 0.5) and sintered at temperatures between 1250 degrees and 1350 degrees C. Major phase BaLa2Ti4O12 and minor phases Ba4Ti13O30 and La4Ti9O24 present in the samples were identified, A Pb additive generally reduced the dielectric constant and enhanced the quality factor of the specimens, except for that prepared at 1250 degrees C, which exhibited the opposite trends. Appreciable replacement of Ba2+ by La3+ and Pb2+ ions was found in the major phase and it effectively reduced the temperature coefficient of resonant frequency tau(f) to 3 ppm/degrees C. The observed variations of microwave properties were interpreted based on microstructural and composition analysis.