A transient technique to measure thermal diffusivity at elevated temperatures

A transient technique for measuring the thermal diffusivity of different so lid materials between room temperature and 1000 degrees C is presented. A t emperature signal is transferred from a filament to the front surface of th e sample and detected with a thermocouple near the front surface. This temp erature signal starts a temperature equilibration process in the sample, wh ich is observed at the rear surface of the sample with a difference thermoc ouple. The transferred heat is an irregular function of the time and is use d to calculate the hypothetical equilibration at the rear surface. Hypothet ical curves are calculated for given thermal diffusivities with a finite-di fference scheme. The thermal diffusivity of the finite-difference scheme is systematically varied to obtain an optimum fit between hypothetical and me asured equilibration behavior. The method is,applied to various materials, such as quartz and C/C-materials of different orientation, a rock sample, a suevite glass and an yttria-stabilized zirconia ceramic. The different the rmal transport mechanisms of the samples (phononic, electronic, advective, radiative) are discussed. Low temperature gradients and small temperature d ifferences in the sample during the experiment allow the measurement of the rmal diffusivities near phase transitions and during mineral reactions. The described method is capable of measuring the thermal diffusivities of soli d samples between 0.1 and 100 mm(2)/s with an internal precision better tha n 3% at temperatures up to 1000 degrees C.