Anharmonic effects in the thermodynamic properties of solids I. An adiabatic calorimeter for the temperature range 25-500 $deg$C: the heat capacities of Al2O3, Al and Pb

The importance of accurate high-temperature thermodynamic data for the study of anharmonic effects in solids is discussed, and an adiabatic calorimeter for the measurement of heat capacities in the temperature range 25-500 °C is described. The precision of the heat capacity data is about ±0·1% for T < 400 °C and ±0·2% for T > 400 °C. Measurement of the heat capacity of a Calorimetry Conference sample of Al 2 O 3 shows that the accuracy of the calorimetry is probably better than ±0·2% throughout the whole temperature range studied. Results have been obtained for lead to near the melting point and for aluminium to 500 °C. For lead a contribution to C p is observed for T > 250 °C which is attributed to vacancy formation; a value of 0·5 2 ±0·2 6 ev is derived for the enthalpy of formation of a vacancy.