Process for semiconductive ceramic body

Claim 1

THE METHOD OF FORMING CERAMIC SEMICONDUCTIVE TITANATE BODY HAVING A RESISTANCE WHICH RISES RAPIDLY WITH TEMPERATURE COMPRISING: FORMING A COHERENT BODY OF TITANATE POWDER CONTAINING A DOPANT, SAID DOPANT BEING A MEMBER OF THE GROUP CONSISTING OF NIOBIUM PENTOXIDE AND LANTHANUM TRIOXIDE IN FROM 0.05 TO 0.18 PERCENT BY WEIGHT OF SAID BODY; HEAT TREATING SAOD BODY IN TWO STAGES AND AT SUBSTANTIALLY UNIFORM RATE WITHIN THE RANGE OF 350*F/HOUR TO 380*F/HOUR, THE FIRST STAGE BEING IN A FIRST OXYGEN-CONTAINING ATMOSPHERE HAVING AN OXYGEN PRESSURE THAT IS EQUAL TO OR LESS THAN THAT OF AIR UNDER STANDARD CONDITIONS, SAID FIRST OXYGEN-CONTAINING ATMOSPHERE HAVING AT LEAST 1% BY VOLUME OF OXYGEN AT A TEMPERATURE AND FOR A TIME SUFFICIENT TO JUST ACHIEVE FULL SECONDARY RECRYSTALLIZATION, AND THE SECOND STAGE BEING IN A SECOND OXYGEN-CONTAINING ATMOSPHERE HAVING AN OXYGEN PRESSURE GREATER THAN THE PARTIAL PRESSURE OF OXYGEN IN AIR UNDER STANDARD CONDITIONS, AT APPROXIMATELY THE SAME TEMPERATURE AS USED IN SAID FIRST STAGE BUT BEING WITHIN ABOUT 2100*F-2800*F AND FOR A TIME SUFFICIENT TO ATTAIN MAXIMUN GRAIN BOUNDARY OXIDATION WITH A MINIMUN OF OXYGEN DIFFUSION INTO THE LATTICE AS INDICATED BY SAID BODY HAVING ITS MOST PRONOUNCED TEMPERATURE DEPENDENCE OF RESISTANCE; AND COOLING SAID BODY IN THE SAME ATMOSPHERE AS EMPLOYED IN SAID SECOND HEAT TREATING STAGE AT A SUBSTANTIALLY UNIFORM RATE WITHIN THE RANGE OF 200*F/HOUR TO 100*F/HOUR TO AT LEAST ABOUT 300*F.

Claim 2

THE METHOD OF FORMING CERAMIC SEMICONDUCTIVE TITANATE BODY HAVING A RESISTANCE WHICH RISES RAPIDLY WITH TEMPERATURE COMPRISING: FORMING A COHERENT BODY OF TITANATE POWDER CONTAINING A DOPANT, SAID DOPANT BEING A MEMBER OF THE GROUP CONSISTING OF NIOBIUM PENTOXIDE AND LANTHANUM TRIOXIDE IN FROM 0.05 TO 0.18 PERCENT BY WEIGHT OF SAID BODY; HEAT TREATING SAOD BODY IN TWO STAGES AND AT SUBSTANTIALLY UNIFORM RATE WITHIN THE RANGE OF 350*F/HOUR TO 380*F/HOUR, THE FIRST STAGE BEING IN A FIRST OXYGEN-CONTAINING ATMOSPHERE HAVING AN OXYGEN PRESSURE THAT IS EQUAL TO OR LESS THAN THAT OF AIR UNDER STANDARD CONDITIONS, SAID FIRST OXYGEN-CONTAINING ATMOSPHERE HAVING AT LEAST 1% BY VOLUME OF OXYGEN AT A TEMPERATURE AND FOR A TIME SUFFICIENT TO JUST ACHIEVE FULL SECONDARY RECRYSTALLIZATION, AND THE SECOND STAGE BEING IN A SECOND OXYGEN-CONTAINING ATMOSPHERE HAVING AN OXYGEN PRESSURE GREATER THAN THE PARTIAL PRESSURE OF OXYGEN IN AIR UNDER STANDARD CONDITIONS, AT APPROXIMATELY THE SAME TEMPERATURE AS USED IN SAID FIRST STAGE BUT BEING WITHIN ABOUT 2100*F-2800*F AND FOR A TIME SUFFICIENT TO ATTAIN MAXIMUN GRAIN BOUNDARY OXIDATION WITH A MINIMUN OF OXYGEN DIFFUSION INTO THE LATTICE AS INDICATED BY SAID BODY HAVING ITS MOST PRONOUNCED TEMPERATURE DEPENDENCE OF RESISTANCE; AND COOLING SAID BODY IN THE SAME ATMOSPHERE AS EMPLOYED IN SAID SECOND HEAT TREATING STAGE AT A SUBSTANTIALLY UNIFORM RATE WITHIN THE RANGE OF 200*F/HOUR TO 100*F/HOUR TO AT LEAST ABOUT 300*F.