5:15 PM - 6:30 PM
[SIT07-P01] Determination of pressure effect on the thermocouple electromotive force using multi-anvil apparatus
Keywords:thermocouple, high-pressure and high-temperature experiments
In this study, we developed a method to determine the absolute pressure effect on thermocouple electromotive force, based on a single wire method using Kawai-type multi-anvil apparatus. By applying this method, single wire EMFs were measured up to a pressure of 7 GPa and temperature of 600°C for chromel and alumel, which passes through the entire length of the pressure medium. The chromel and alumel wires were contained in semi-sintered MgO and dense Al2O3 insulating tubes, and the portions of the wires in MgO and Al2O3 were subjected to higher and lower pressures, respectively. The temperature along the single wires was calibrated by separate experiments employing multiple thermocouples. Pressure conditions along the wires were evaluated based on in situ X-ray diffraction using synchrotron X-ray radiation and a thermal equation of state of Ni. The pressure effect of the Seebeck coefficients of chromel and alumel, determined by the analyses of single wire EMFs and pressure-temperature profiles along the wires, was virtually consistent with that of previous lower-pressure or lower-temperature studies. The difference between the nominal temperature by chromel-alumel thermocouple (type K) and the real temperature was calculated to be from 0 to –3°C in conditions up to 7 GPa and 600°C. Since the multi-anvil apparatus is capable of achieving much higher pressure and temperature, the method presented in this study promises to reveal absolute temperature correction for thermocouples over a wide range of pressure and temperature conditions.