Improvement in the microwave dielectric properties of SrCa4Nb4TiO17 ceramics by Ba substitution

Microwave dielectric ceramics in the Sr1- (x) Ba (x) Ca4Nb4TiO17 (0 a parts per thousand currency sign x a parts per thousand currency sign 0.75) composition series were fabricated via a solid-state mixed oxide route. All the compositions formed single phase in Sr1- (x) Ba (x) Ca4Nb4TiO17 (0 a parts per thousand currency sign x a parts per thousand currency sign 0.75) solid solutions within the detection limit of in-house X-ray diffraction (XRD). The sintered microstructure of these ceramics comprised densely packed elongated and plate-like grains. The dielectric properties varied linearly with x. Relative permittivity (epsilon (r)) increased from 47.2 to 54.5, unloaded quality factor multiplying the resonant frequency (Q (u) f (o)) decreased from 11,984 to 9345 GHz and temperature coefficient of resonant frequency (tau (f)) increased from -78.6 to 20 ppm/A degrees C with an increase in x from 0 to 0.75. In the present study, epsilon (r) a parts per thousand 51.6, Q (u) f (o) a parts per thousand 10,160 GHz (5.37 GHz) and tau (f) a parts per thousand -13.5 ppm/A degrees C were achieved for Sr0.5Ba0.5Ca4Nb4TiO17 (x = 0.5) ceramics.