Low-loss and temperature-stable (1−x)Li2TiO3–xLi3Mg2NbO6 microwave dielectric ceramics

Abstract

Low-loss (1−x)Li2TiO3–xLi3Mg2NbO6 (LT-LMN, 0.02 ≤ x ≤ 0.08) microwave dielectric ceramics (MDCs) with rock salt structures were fabricated via a traditional solid-state reaction route. Li3Mg2NbO6 was used as a Li2TiO3 compensator to improve temperature stability. Scanning electron microscope observations and X-ray diffraction analyses were used to investigate the microstructures and crystalline structures of the ceramics, respectively. We demonstrated a correlation between macroscopic “dark hole” phenomena and the microwave dielectric properties (MDPs) of LT-LMN ceramics by analysing the valence states of Ti ions and the content of oxygen vacancies using X-ray photoelectron spectra. We continuously added Li3Mg2NbO6 to pure Li2TiO3 to form MDCs, and found that at x = 0.04, (1−x)Li2TiO3–xLi3Mg2NbO6 ceramics achieved a near-zero resonance-frequency temperature coefficient (τf). 0.96Li2TiO3–0.04Li3Mg2NbO6 ceramics sintered at 1250 °C had excellent MDP values: appropriate permittivity (ϵr) = 19.12, high quality factors (Q × ƒ) = 70814 GHz (at 6.105 GHz), and τf = 2.6 ppm/°C. This indicates that LT-LMN ceramics are promising materials for high-selectivity microwave ceramic dielectric substrates.