Electrical resistivity at the micron scale in a polycrystalline SiC ceramic

Abstract

Grain boundaries typically dominate the electrical properties of polycrystalline ceramics. To understand the effect of grain boundaries on the electrical conductivity of SiC ceramics sintered with 2000 ppm Y2O3, the electrical resistivity of individual grains and multi-grains across boundaries at the micron scale was measured using a nano-probing system equipped with nano-manipulators. The results revealed that grain resistivity was bimodal because of the existence of a core/rim structure in grains, and the electrical resistivity of multigrain samples slowly increased with an increase in the number of grain boundaries crossed. Specifically, the electrical resistivity of a grain without a core, a grain with a core, a bicrystal with a single boundary, a sample crossing three boundaries, and a bulk polycrystalline sample were 2.36 × 10-1, 5.05 × 10-1, 4.80 × 10-1, 5.04 × 10-1, and 5.84 × 10-1 Ω cm, respectively. The results suggest that the electrical resistivity of polycrystalline SiC ceramics is primarily influenced by the presence of a grain boundary or core and secondarily by the number of boundaries.