MoSi 2 -and WSi 2 -based electroconductive ceramic composites were fabricated using 40-80 vol% fine-and coarse-Al 2 O 3 , and ZrO 2 particles (refractory oxides) after sintering in argon. Their chemical and thermal stability was tested between 1400°C-1600°C for up to 48 hours. X-ray diffraction analysis showed the formation of secondary 5-3 metal silicide (Mo 5 Si 3 , W 5 Si 3 ) and silica phases on the grain boundaries and surface. The fraction of the W 5 Si 3 (11.4-38.8 vol%) was significantly higher than that of the Mo 5 Si 3 (3.3-7.3 vol%) in the composites after annealing at 1400°C for 48 hours. The rates of grain growth in the composites (0.013-0.023 lm/h) were highly decreased by a grain-boundary pinning effect.This effect was relatively better with the addition of the coarse-grained oxides due to their more homogeneous distribution throughout the microstructure. The 20-80 vol% MoSi 2 -Al 2 O 3 (fine-grained) composite exhibited an electrical conductivity of 8.8 S/cm at 900°C. At the 60 vol% silicide content, MoSi 2 -Al 2 O 3 (coarse-grained) and WSi 2 -Al 2 O 3 (fine-grained) showed higher electrical conductivity (126-128 S/cm) at 900°C. The density, porosity level, particle distribution, intrinsic conductivity of silicide phase, particle size, and fraction of the secondary 5-3 silicide phase highly influenced their electrical properties.