Heat capacities measurements at low-temperatures 5-300K

The need for low-temperature heat capacity and the resulting standard-entropy data is given by the fact, that there are no direct measurements of heat capacities at low-temperatures for a great number of important hydrous rock forming minerals, especially for phases of the low to medium metamorphic grade, e.g. chloritoid solid solution (s.s.), magnesio-and ferropumpellyite s.s., clinozoisite-epidote s.s., the zeolites laumontite and wairakite, the smectite montmorillonite. The knowledge of these thermodynamic properties is a requirement for quantifying natural processes, such as the metamorphic or magmatic evolution of a crustal segment. In addition, low- temperature heat capacity measurements are an important experimental source of data to characterize the magnetic properties of Fe end-member silicates. The effect of magnetic ordering has to be accounted for when calculating e.g. the standard entropy of a Fe end-member silicate. Heat capacities at low-temperatures can be measured successfully with the Physical Property Measurement System (PPMS, produced by Quantum Design, Inc., San Diego, CA 92121, USA) at the Department Material Science, University of Salzburg. The PPMS is a quasi-adiabatic low-temperature calorimeter based on the principles of heat pulse calorimetry (HPC). This microcalorimeter is designed for measuring the low-temperature heat capacities of milligram-sized samples with high accuracy and precision as shown by Dachs and Bertoldi (2005). The above listed solid solutions and mineral species as well as prehnite and lawsonite will be characterized chemically and investigated by PPMS to yield reliable heat capacity data at low temperatures.