A novel low-permittivity LiAl0.98(Zn0.5Si0.5)0.02O2-based microwave dielectric ceramics for LTCC application

Phase composition, morphology, and microwave dielectric properties of (1-x) LiAl0.98(Zn0.5Si0.5)(0.02)O-2 + x CaTiO3 (0.05 <= x <= 0.20) materials synthesized via the solid state reaction method were investigated. All these densified materials were obtained at a sintering temperature of 1150 degrees C. All compositions showed a major LiAlO2 phase that was accompanied by a minor CaTiO3 phase. The epsilon(r) value increased gradually from 10.88 to 11.60, whereas the Q x f value remarkably decreased from 33 251 GHz to 13 511 GHz. The tau(f) value changes from -85 ppm/degrees C to 212 ppm/degrees C, thereby indicating that CaTiO3 could effectively adjust this value. HBO3-doping was used to further decrease the sintering temperature to 900 degrees C. The optimum value was obtained at 7 wt.% HBO3 doped with microwave dielectric properties of epsilon(r) = 9.39, Q x f = 10 224 GHz, and tau(f) = -7.8 ppm/degrees C. This material also exhibited chemical compatibility with silver, making it a candidate for low temperature co-fired ceramics applications.