Calibration of Capacitive Cells for Dilatometric Measurements of Thermal Diffusivity

The relationship between capacitive signal and variable gap size between the capacitor plates of the cell can be obtained by heating a copper disc which transmits its thermal expansion to the sample without exchanging heat with the sample itself. The method allows the determination of thermal diffusivity with a repeatability of about 3% for low conducting materials with thermal expansion coefficients greater than 0.5*10-5 K-1.