Microstructural, electrical, and mechanical properties of conductive SiC ceramics fabricated by spark plasma sintering

Abstract

Nitrogen (N)-doped conductive silicon carbide (SiC) of various electrical resistivity grades can satisfy diverse requirements in engineering applications. To understand the mechanisms that determine the electrical resistivity of N-doped conductive SiC ceramics during the fast spark plasma sintering (SPS) process, SiC ceramics were synthesized using SPS in an N 2 atmosphere with SiC powder and traditional Al 2 O 3 -Y 2 O 3 additive as raw materials at a sintering temperature of 1850-2000 • C for 1-10 min. The electrical resistivity was successfully varied over a wide range of 10 −3 -10 1 Ω cm by modifying the sintering conditions. The SPS-SiC ceramics consisted of mainly Y-Al-Si-O-C-N glass phase and N-doped SiC. The Y-Al-Si-O-C-N glass phase decomposed to an Si-rich phase and Ndoped Y x Si y C z at 2000 • C. The Vickers hardness, elastic modulus, and fracture toughness of the SPS-SiC ceramics varied within the ranges of 14.35-25.12 GPa, 310.97-400.12 GPa, and 2.46-5.39 MPa m 1/2 , respectively. The electrical resistivity of the obtained SPS-SiC ceramics was primarily determined by their carrier mobility.

Electromagnetic wave absorption properties of hot‐pressed Si3N4‐SiC ceramic nanocomposites

“…Element dissolution, diffusion, and grain growth are all involved in the solution‐precipitation process, which has an important influence on the electrical conductivity of ceramics containing SiC semiconductor phases 30 . It has been demonstrated that nitrogen elements could dope into SiC crystals during their grain growth in the LPS process 31,32 . After doping, a donor level is created in the band gap of β‐SiC by replacing carbon atoms with incorporated nitrogen atoms, improving the electrical conductivity of ceramic composites.…”

“…30 It has been demonstrated that nitrogen elements could dope into SiC crystals during their grain growth in the LPS process. 31,32 After doping, a donor level is created in the band gap of β-SiC by replacing carbon atoms with incorporated nitrogen atoms, improving the electrical conductivity of ceramic composites. During sintering of the Si 3 N 4 -SiC ceramic nanocomposites, the nitrogen elements from the nitrogen atmosphere and Si 3 N 4 particles dissolve into the intergranular phases and then incorporate into SiC nanograins during grain growth.…”