Composite dielectric ceramics based on BaO-Ln2O3-TiO2 (Ln = Nd, La)

BaLa4Ti4O15 (BLT) is a hexagonal perovskite-related compound with a temperature coefficient of resonant frequency (tau(f)) of -2ppm/degrees C, relative permittivity (epsilon(Gamma)) similar to 44 and figure of merit (Q (.) f) similar to 44000GHz. Ba4Nd9.333Ti18O54 (BNT) has a tungsten-bronze-related structure with epsilon(Gamma) similar to 78, Q (.) f approximate to 11000 GHz and tau(f) of +47 ppm/degrees C. The microstructures and microwave dielectric properties of xBNT-(1 - x)BLT (0 <= x <= 1) composite ceramics have been studied. X-ray diffraction analysis and scanning electron microscopy revealed that there was limited inter-reaction between the two phases and that samples were composed largely of BNT and BLT, although some deterioration in measured Er with respect to calculated values was observed. The optimum compositions were x = 0.55 and 0.75 for which epsilon(Gamma) similar to 63, tau(f) similar to -20ppm/degrees C and Q (.) f > 10,000 GHz.