Composite dielectric ceramics based on BaO-Ln2O 3-TiO2 (Ln = Nd, La)

Abstract

BaLa4Ti4O15 (BLT) is a hexagonal perovskite-related compound with a temperature coefficient of resonant frequency (τf) of -2ppm/°C, relative permittivity (εr) ∼ 44 and figure of merit (Q · f) ∼ 44000 GHz. Ba4Nd9.333Ti18O54 (BNT) has a tungsten-bronze-related structure with εr, ∼ 78, Q · f ≈ 11000 GHz and τf of +47 ppm/°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 εr with respect to calculated values was observed. The optimum compositions were x = 0.55 and 0.75 for which εr ∼ 63, τf ∼ -20ppm/°C and Q · f > 10,000 GHz. © 2005 The Japan Society of Applied Physics.