Influence of synthesis process on the dielectric properties of B-doped SiC powders

Fine powders (similar to 0.7 mu m) of SiC doped with 3 mol% and 10 mol% B were successfully produced by mechanical activation assisted self-propagating high-temperature synthesis (MASHS). The experimental results showed that the presence of B caused a reduction in the combustion temperature, shrinkage of the crystal lattice, an increase in the tendency of the grains to be crystallized, and a decrease in the dielectric properties in the frequency range between 8.2 and 12.4 GHz, specifically the real (epsilon') and the imaginary parts (epsilon '') of complex permittivity and the loss tangent (tan delta). Analysis of the results suggests that B ions should be preferably accommodated in the Si sites of the SiC lattice and cause a reduction in the number of defects (V-si, V-c, and C-si), which results in a decrease in the dielectric properties. Comparison of the experimental results of this study with results reported in similar earlier studies reveals that the influence of B on the dielectric properties of the B-SiC powders depends strongly on the synthesis process. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.