Relationship between structure and properties of microwave dielectric ceramic Li(1+x)2MgTi3O8 based on Li non-stoichiometry

Abstract

Li(1+x)2MgTi3O8 (0.0 ≤ x ≤ 0.10) ceramics with Li non-stoichiometric ratios were prepared by the solid-state reaction method to inhibit the volatilization of Li. The effects of the Li non-stoichiometric ratios on the sintering behavior, crystal structure, microscopic morphology, Raman vibrations, electron density, and dielectric properties of Li(1+x)2MgTi3O8 ceramics were systematically investigated. The Li(1+0.06)2MgTi3O8 ceramics demonstrate the best dielectric properties with εr = 26.33, Q × f = 69 435 GHz (@6.87 GHz, 54% improvement), τf = 2.95 × 10−6 °C−1. For the non-intrinsic factors, the high relative density (97.15%) and larger grain size (16.78 μm) allow the dielectric properties to be improved. As for the intrinsic factors, a reasonable excess of Li improves the bond ionicity of the Mg—O bond, the lattice energy of the Ti—O bond, and the electron cloud density, thus optimizing the dielectric properties. Raman spectroscopy leads to the same result from the point of view of lattice vibrations. At the same time, the distortion of the polyhedra is also improved, so that τf also approaches 0. The improved Li(1+0.06)2MgTi3O8 has potential applications in microwave communication technology.

Keywords

• Li(1+x)2MgTi3O8
• Raman vibration
• First-principles
• P-V-L theory
• Microwave dielectric