The present invention discloses a new type of electrodeless light sources, which can be achieved by radiating microwave on an inorganic carbide with electrical conductivity. The inorganic carbide can be carbon nanotubes (CNTs), or graphite-related fiber materials with well-order crystalline structure. The inorganic carbides of the present invention also emit high-brightness white light source in low vacuum condition (less than 10 torr) and induce plasma gas discharge emission in the presence of a trace of inert gas molecules such as nitrogen and argon. The electrodeless light source of the present invention not only emits high-brightness light emissions but also performs low thermal-radiation conversion.