The structural characteristics and microwave dielectric properties of (Mg0.5Ti0.5)3+ substituted Sr0.6Ca0.4LaAlO4 ceramics

Abstract

Achieving both high Qf and near-zero τf values for microwave dielectric ceramics in the microwave frequency band is challenging. In this work, the effect of (Mg0.5Ti0.5)3+ substitution on the structural characteristics and microwave dielectric properties of Sr0.6Ca0.4LaAlO4 ceramics was systematically investigated. The Sr0.6Ca0.4LaAl1-x(Mg0.5Ti0.5)xO4 (x = 0–0.5) ceramics were successfully synthesized. The average bond length of Sr/Ca/La–O for Sr0.6Ca0.4LaAl1-x(Mg0.5Ti0.5)xO4 ceramics is related to the dielectric constant (εr). The relative density of the ceramics and FWHM of the Raman peak have strong effects on the Qf values. There is a dependence of the [AlO6] octahedral distortion on the τf values, which provides new possibilities for tuning the temperature coefficient of the K2NiF4-type ceramics. When x is 0.4, the excellent microwave dielectric properties are obtained as following: εr = 20.52, Qf = 103,600 GHz (at 7.79 GHz), and τf = −3.77 ppm/°C. The above work provides a deeper insight into the relationship between the crystal structure characteristics and the microwave dielectric properties of the K2NiF4-type ceramics.