Production of Ni-doped SiC nanopowders and their dielectric properties

Nanopowders of nickel-doped β-silicon carbide (β-SiC) with improved dielectric properties (compared with pure β-SiC) were successfully produced using the mechanically activated self-propagating high-temperature synthesis method in an argon (Ar) atmosphere. The molar substitution of nickel (Ni) for silicon (Si) was 1%, 3%, and 5%. Powders of poly(tetrafluoroethylene) and ammonium chloride (NH₄Cl) were used to promote the combustion reaction. The experimental results indicated an active role of Ni in the mechanism of combustion synthesis of SiC powders, which was reflected in the increase in combustion temperature and the velocity of propagation of the combustion wave, the microstructure of the produced nanopowders with a grain size of 100 nm for 5% Ni, and an improvement in the dielectric properties, specifically the increase in real (ε′) and imaginary parts (ε″) of the complex permittivity, in the frequency range of 8.2-12.4 GHz, compared with pure SiC. The X-ray analysis of the produced powders suggests that Ni is accommodated in the lattice of SiC, which shrinks with increasing amounts of Ni.