Microwave dielectric properties and microstructure of Ba6−3xNd8+2xTi18−y(Cr1/2Nb1/2)yO54 ceramics

Abstract The microwave dielectric properties and the morphology of Ba 6−3x Nd 8+2x Ti 18−y (Cr 1/2 Nb 1/2 ) y O 54 (x = 0.75, 0 ≤ y ≤ 3.0) ceramics prepared under different sintering conditions were investigated in this work. The effects of substitutions on the microstructure and microwave dielectric properties were discussed. The X-ray diffraction (XRD) patterns of the sintered samples revealed a single-phase formation BaNd 2 Ti 4 O 12 with a tungsten bronze type structure in the system. The results of energy dispersive spectrometer (EDS) and lattice parameters calculated on XRD data could confirm the substitution at B-site. A small amount of substitutions improved quality factor value (Q × f) and the temperature coefficient of resonant frequency (τ f ) but led to a decrease of the permittivity. The temperature coefficient of resonant frequency (τ f ) was found to decrease with increasing substitutions because of the declination of tolerance factor (t). And the τ f could be adjusted from +62.4  ppm/°C to −7.3  ppm/°C with increment of substitutions. Finally, excellent dielectric properties were obtained as y was 0.5 sintered at 1400 °C for 2 h in air: e r  = 88.6, Q × f = 11486 GHz, τ f  = +37.1  ppm/°C.