Synthesis and characterization of silica sand-derived nano-forsterite ceramics

摘要

This paper reports the synthesis and structural, microstructure, and dielectric characterizations of nanosized forsterite powders and their ceramics. Forsterite powder was synthesized by the mechanical activation of starting materials magnesium oxide (MgO) and amorphous silica (SiO2) powders followed by calcination at 950 degrees C. The amorphous silica powder was obtained by processing local silica sand. The compound analysis of forsterite powder was performed by FTIR spectroscopy, phase analyses by XRD, and the particle size was found by TEM. The ceramics were synthesized by uniaxially pressing the powder and then sintering it at 950, 1050, 1150, and 1200 degrees C. Characterization of the ceramics included microstructure, diameter shrinkage, density, porosity, dielectric constant and quality factor. Results showed that the synthesized powder consisted of nano sized (ca. 55 nm) forsterite (Mg2SiO4) as the main phase, accompanied by protoenstatite (MgSiO3), periclase (MgO), and low cristobalite (SiO2) as minor phases. The sintered ceramics exhibited improved forsterite weight fraction with a maximum of 99.3% after sintering at 950 degrees C. Furthermore, with the increase in sintering temperature from 950 to 1200 degrees C, the density of the ceramics increased from 1.6 to 2.5 g cm(-3) and also led to grain growth from 56 to 277 nm. Furthermore, their 10-GHz dielectric constants (epsilon(gamma)') were relatively low, i.e., between 6.0 and 13.3. In addition, all the ceramic samples had a loss factor tan delta 0.0004 and a quality factor Q x f 1000 GHz, which indicates that the dielectric properties of all the samples can be promoted as those of millimeter-wave candidate materials.