Abstract
Theoretical analysis is given for classical DTA, power-compensated DSC and heat-flux DSC, based on a unified model which is applicable to all the three types of instruments. The equation governing heat flow within the system are solved analytically assuming constant heat capacity and thermal conductivity. The method of estimating the actual temperature is given in the case of the first-order phase transition. A principle of drawing the base line is given for determining the enthalpy of the first-order phase transition. Applying the principle to the unified model, theoretically rigorous drawing of the base line is shown in the case that the heat capacities before and after the transition are different. Theoretical peak height due to the first-order phase transition is represented as a function of the heat capacity, the thermal resistance and the heating (cooling) rate. It is shown that the limiting peak height obtainable in the experiments is independent of the amount of the sample. A possibility is discussed of quantitative determination of the enthalpy of transition by using classical DTA.
