Low temperature calorimetry and its application in material research

Abstract

Low temperature calorimetry is an experimental method of specific-heat measurement of condensed matters, and the specific heat is one of the most important and fundamental thermodynamic properties. There are mainly four methods of specific heat measurement, including adiabatic, relaxation, AC and continuing heating calorimetry. The adiabatic calorimetry is the most accurate and reliable in the specific heat measurement, since it is a static method that the sample can reach a thermal equilibrium during the measurement. However, there is no commercial adiabatic calorimeter yet because of complicated instrumentation, time consuming experimental procedures, and large sample amount requirements. The other three are dynamic specific heat measurement method, in which the sample is measured in a heating manner, and consequently a good thermal conductivity is required for a sample to obtain a reliable measurement. The specific heat is a bulk property of substance, and it can provide an average measure of the thermal properties of a sample. It is well known that the condensed states of matters are mainly controlled by the molecular motions, intermolecular interactions, and interplay among molecular structures. The physical property reflected in a material may be closely related to the energy changes in these three factors, which can be directly observed in a specific heat curve. Therefore, specific-heat measurements have been used not only to obtain entropy, enthalpy and Gibbs free energy, but also to investigate and understand lattice vibrations, metals, superconductivity, electronic and nuclear magnetism, dilute magnetic systems and structural transitions.