Methods for making high-temperature thermocouples

A method of heat-treating a thermocouple, comprising:

• measuring an output voltage of a thermocouple while exposing a first thermoelement wire and a second thermoelement wire to a temperature between 50° C. to 60° C. above a predetermined operational temperature of the first and second thermoelement wires;
• and
• maintaining the first thermoelement wire and the second thermoelement wire exposed to the temperature until a rate of change of a normalized voltage output of the first thermoelement wire and the second thermoelement wire is between 0.001 normalized Volts per hour and 0.0001 normalized Volts per hour.

A thermocouple subjected to a method of heat treating, the method comprising:

• exposing a thermocouple junction comprising a first thermoelement wire and a second thermoelement wire to a temperature in a range extending from 50° C. to 60° C. above an intended operational temperature of the first and second thermoelement wires and until a rate of change of a normalized voltage output of the first thermoelement wire and the second thermoelement wire is 0.001 normalized Volts per hour or less than 0.001 normalized Volts per hour, wherein the first thermoelement wire comprises a molybdenum-lanthanum based material and the second thermoelement wire comprises a phosphorus-doped niobium.