Crystal structure, Raman spectra, and microwave dielectric properties of a novel temperature-stable LiY9Si6O26 ceramic with hexagonal structure

Abstract

This study presents a comprehensive investigation into the dielectric properties of LiY9Si6O26 ceramics, which were prepared for the first time using the solid-state method. XRD patterns and Rietveld refinement analysis conclusively demonstrate that LiY9Si6O26 adopts a hexagonal crystal structure with space group P63/m (176). Furthermore, Raman spectroscopy reveals a significant correlation between the quality factor and the FWHM of the A1g(O) mode at 879 cm−1. Transmission electron microscopy (TEM) was employed to verify the ordered layered structure inherent in the hexagonal LiY9Si6O26 ceramics. The microstructure of the ceramic grains was analysed using scanning electron microscopy (SEM), which revealed a remarkably high relative density of 96.4% for the LiY9Si6O26 ceramic. The Si–O bond valences (VSi–O) were found to be closely associated with the τf in LiY9Si6O26 ceramics. Remarkably, the microwave dielectric properties of LiY9Si6O26 ceramics sintered at 1425 °C were ascertained to be εr = 10.54, Q × f = 25,579 GHz (f = 10.3 GHz), and τf = 2.64 ppm/°C. These outstanding properties position LiY9Si6O26 ceramics as promising candidates for high-performance dielectric materials.