Relationship between the structure and microwave dielectric properties of non-stoichiometric Li2+xSiO3 ceramics

Abstract Li 2 SiO 3 ceramic is one of the most important candidate materials for high-frequency microwave ceramics; however, minimal information about the relationship between the structure and microwave dielectric properties of non-stoichiometric Li 2+ x SiO 3 ceramics is available. In the present work, nominal Li 2+ x SiO 3 ( x =0, 0.04, 0.08, 0.12 and 0.16) ceramics were prepared by a conventional solid-state sintering technique. The structure of Li 2+ x SiO 3 ceramics was investigated via X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) as well as Raman spectra experiment and calculation. Refinements showed that part of the non-stoichiometric Li ions entered the Li 2 SiO 3 lattice. Along with the results of the XRD analysis, Raman spectra experiment and calculation confirmed the presence of Li 2 Si 2 O 5 phase in all the samples. Compared with stoichiometric Li 2 SiO 3 , non-stoichiometric Li provided higher densification and less ordering. Moreover, the SiO 4 tetrahedrons formed more ionic bonds, which reduced distortion polarization. Further, the dielectric constants, which were observed to be mainly dependent on distortion polarization and densification, firstly increased then decreased slightly with increasing non-stoichiometric Li content. However, the quality factor ( Q×f ), which was primarily driven by ordering degree of Li-O bonds, firstly decreased then increased with increasing non-stoichiometric Li content. The results obtained on the Li 2+ x SiO 3 ceramics, might offer some useful information for study and application about high-frequency microwave.