Crystal structure and microwave dielectric properties of garnet-type Ca2YZr2-xTixAl3O12 ceramics for dual-band bandpass filters

Abstract

Microwave dielectric ceramics with a high-quality factor are vital materials for substrates, dielectric resonators, and filters in millimeter-wave communication systems. Here, a novel microwave dielectric ceramic based on a garnet-type Ca2YZr2Al3O12 compound for bandpass filter was prepared using the solid-state reaction method. Sintering the Ca2YZr2Al3O12 ceramics at 1600 ℃ for 5 h resulted in excellent microwave dielectric properties of εr = 10.81 ± 0.16, Qf = 87,628 ± 4000 GHz and τf = −34.3 ± 0.5 ppm/℃. Increasing the Ti4+ content of the Ca2YZr2-xTixAl3O12 ceramics significantly improved the sintering process. Superior microwave dielectric properties (εr = 11.93 ± 0.15, Qf = 121,930 ± 2600 GHz and τf = −30.8 ± 0.4 ppm/℃) were obtained for Ca2YZr2-xTixAl3O12 (x = 0.3) because of its dense microstructure, large grain size and high lattice energy. The Ca2YZr2-xTixAl3O12 (x = 0.3) ceramics were used to fabricate a dual-band bandpass filter with a hairpin structure that exhibited a large return loss (|S11| > 12 dB) and a small insertion loss (|S21| < 0.73 dB). The high performance of the Ca2YZr2-xTixAl3O12 ceramics and the corresponding bandpass filter makes this material a potential candidate for millimeter-wave devices.