Electrically conductive Si.sub.3 N.sub.4 -C series amorphous material and a method of producing the same

A method of producing massive and pure Si.sub.3 N.sub.4 -C series amorphous material composed of a deposited amorphous Si.sub.3 N.sub.4 matrix and codeposited carbon uniformly distributed in said matrix, having an electrical conductivity .sigma. of a formula

• .sigma.=.sigma..sub.o exp(-E/2kT)
• wherein .sigma..sub.o is an electrical conductivity at 0.degree. K., E is a value of 0.02-0.06 eV, k is the Boltzmann constant and T is an absolute temperature, a carbon content of about 0.2-10% by weight, an electrical conductivity .sigma. of about 10.sup.-3 to 10.sup.-1 .OMEGA..sup.-1 cm.sup.-1 at a temperature from ambient to about 900.degree. C., a density of about 2.7 to 3.0 g/cm.sup.3, a thermal conductivity of about 0.004-0.010 cal/cm.multidot.sec.multidot.K at ambient temperature, a specific heat of about 0.16 cal/g.multidot.K at ambient temperature, a thermal diffusivity of about 0.010-0.022 cm.sup.2 /sec at ambient temperature, and a micro Vickers hardness of about 2,500-3,500 kg/mm.sup.2 (100 g load) at ambient temperature by chemical vapor deposition process, which comprises reacting SiCl.sub.4 as silicon source gas, a nitrogen source gas and a hydrogen source gas with a carbon source gas at a deposition condition of a deposition temperature of about 1,100.degree. to 1,300.degree. C. under a reduced total pressure of about 30-70 mmHg in a reaction furnace to deposit the Si.sub.3 N.sub.4 -C series amorphous material on a surface of a substrate selected from the group consisting of graphite, silicon carbide and silicon nitride, the substrate being heated to said deposition temperature.