Microwave dielectric properties, Raman spectra and sintering behavior of novel low loss La7Nb3W4O30 ceramics with rhombohedral structure

Abstract

This study introduced a novel low-loss tungstate ceramic, La7Nb3W4O30 (LNWO), synthesized using the solid-state techniques. The structural analysis of the La7Nb3W4O30 ceramic material, utilizing X-ray diffraction (XRD) patterns and followed by detailed structural refinement, validated its rhombohedral structure. Transmission electron microscopy (TEM) was utilized to confirm the ordered layer arrangement characteristic of the rhombohedral structure. The internal structure was characterized by scanning electron microscopy (SEM), with the sample's relative density reaching 97.5 %. The correlation between the full width at half maximum (FWHM) of the Raman matrix at 901 cm−1 corresponding to the symmetric bending mode vibrations of WO5 and the Q × f value was discussed. Furthermore, the main factors affecting the dielectric constant, including density, bond valence, secondary phases, and variations in porosity, were analyzed. Encouragingly, the ceramic showed significant microwave dielectric properties when it was sintered at 1425 °C (εr = 23.68, Q × f = 26,687 GHz (f = 7.2 GHz), τf = −35.2 ppm/°C).