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

Abstract

Microwave dielectric ceramics in the Sr_{1− x} Ba _x Ca₄Nb₄TiO₁₇ (0 ≤ x ≤ 0.75) composition series were fabricated via a solid-state mixed oxide route. All the compositions formed single phase in Sr_{1− x} Ba _x Ca₄Nb₄TiO₁₇ (0 ≤ x ≤ 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 (ε _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 (τ _f) increased from −78.6 to 20 ppm/°C with an increase in x from 0 to 0.75. In the present study, ε _r ≈ 51.6, Q _u f _o ≈ 10,160 GHz (5.37 GHz) and τ _f ≈ −13.5 ppm/°C were achieved for Sr_0.5Ba_0.5Ca₄Nb₄TiO₁₇ (x = 0.5) ceramics.