XIONG Houbo ¹, WANG Geng ², WANG Yuan ¹, WANG Wenqiang ³, CHENG Jiatai ⁴

(1. College of Electrical and Electronic Engineering, Hubei University of Technology, Wuhan 430068, Hubei, China; 2. College of Electronics and Information Engineering, Hubei University of Science and Technology, Xianning 437100, Hubei, China; 3. School of Materials Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen 333403, Jiangxi, China; 4. Jiangxi Bocent Advanced Ceramic Co., Ltd., Pingxiang 337200, Jiangxi, China)

Abstract: Ba₄Pr_28/3Ti_18-yAl_4y/3O₅₄(0≤y≤2) microwave dielectric ceramics were prepared by using the standard solid-state reaction method. The effect of Al³⁺ substitution on phase composition, microstructure and microwave dielectric properties was studied by using X-ray diffraction (XRD), back-scattering (BSE) and X-ray energy spectrometer (EDS). It is found that all the samples were of orthogonal tungsten-bronze structure as the major phase. The unit cell parameters and unit cell volume were decreased first and then increased with increasing substitution content of Al³⁺. According to the BSE and EDS results, single-phase structure was observed in the samples with 0≤y≤1.5, while a trace of second phase was present in the one with y = 2.0. The grain size and the length of the columnar grains were decreased as the content of Al³⁺ was increased. Al³⁺ substitution could effectively improve the quality factor (Q×f) and reduce the temperature coefficient of resonance frequency (TCF), but decrease the dielectric constant (ε_r). Specifically, the Ba₄Pr_28/3Ti_18-yAl_4y/3O₅₄ ceramics with y = 1.5 exhibited optimal microwave dielectric properties, with ε_r = 76.6, Q × f = 10800 GHz and TCF = +55 ppm/°C.
Key words: Ba₄Pr_28/3Ti_18-yAl_4y/3O₅₄ ceramics; Tungsten-bronze structure; microwave dielectric properties