Synthesis and microwave dielectric properties of Si/C/B powder

Si/C/B powders were synthesized by carbothermal reduction of xerogels containing boride. Colorless, transparent and monolithic gel was obtained by using tetraethoxysilane, saccharose, tributyl borate, ethanol and distilled water as starting materials. When the xerogel was fired at 1 600 °C in the static argon atmosphere, the XRD pattern commences to show the crystallite peak corresponding with C. β-SiC was synthesized at 1 700 °C, but amorphous remainders could not be eliminated completely. The XRD results show that the boron possibly enters into the silica network, leading to the formation of borosiloxane. Microstructure of β-SiC powders consists of agglomerated particles with diameters ranging from 30 to 100 nm. Though the samples prepared at 1 600 °C and 1 700 °C have better dielectric loss tangent than the sample at 1 500 °C due to exiting crystalline material, the dielectric constant and dielectric loss tangent of three samples reveal lower values.