Refractory-oxide-based incandescible radiators and method of making

A refractory-oxide-based elongated incandescent radiator body member adapted for operation by application of a predetermined electric potential across the ends thereof, said body member comprising:

• a. an elongated member principally comprising sintered ceria-doped thoria or chromia-doped alumina refractory oxide which in a pure state appears generally light in color;
• b. discrete refractory metal tungsten particles dispersed through said oxide in amount of from about 8 volume percent to about 20 volume percent of said member, and said member as initially sintered during fabrication thereof having sufficient resistivity that said member will not self-resistance heat to a condition of incandescence upon application of said predetermined electric potential across the ends thereof;
• c. said member having been further processed after being initially sintered by heating said member under non-reactive conditions to a temperature of at least about 1400.degree. C while simultaneously placing said member within the influence of an electric field having an intensity of at least about 5 volts/mm but insufficient to cause said member to fracture;
• and
• d. said simultaneously heating and application of said field causing said discrete metal particles to have therebetween sufficient electrical continuity to enable said member to be self-resistance heated to an incandescent state upon application of said predetermined electric potential across the ends thereof.

The method of preparing a cermet body which will display increased electrical conductivity at room temperature, said method comprising:

• a. preparing a mixture of finely divided refractory oxide and finely divided refractory metal, with said refractory metal present in the amount of from about 8 volume percent to about 20 volume percent of said mixture;
• b. forming said mixture into a self-sustaining member having a predetermined configuration which approximates that desired for said cermet body;
• c. presintering said self-sustaining member under non-reactive conditions to provide said member with a density which is from about 75% to about 86% of theoretical;
• d. treating said presintered member by heating said under non-reactive conditions at a temperature of at least about 1400.degree. C while simultaneously subjecting said member to the influence of an electric field having an intensity of at least about 5 volts/mm but insufficient to cause said member to fracture;
• and
• e. final sintering said treated member under non-reactive conditions to achieve a desired density.