Low-temperature heat capacities (cp) for milligram(mg)-sized samples of corundum, fayalite and sanidine were measured with a recently available commercial calorimeter (the heat capacity option of the Physical Properties Measurement System (PPMS), produced by Quantum Design®, which operates on the basis of a heat-pulse technique. The measurements were performed between 5 and 300 K on synthetic single-crystals and powders. Since cp-data for the above minerals are known from low-temperature adiabatic calorimetry (low-TAC) these data were used to constrain the accuracy of the PPMS-calorimeter in measuring their cp on mg-sized samples.

A relative uncertainty (100*σcp/cp), as a measure of precision, of ~0.3% for T > 50 K, increasing to ~0.5% for T < 50 K, was obtained in our heat capacity measurements using single-crystals weighing 10-50 mg and sintered powder weighing 48 mg. The precision was lower when the cp was measured for sample powders that had been sealed in Al-pans (0.5 ± 0.2% relative uncertainty at T > 100 K, 2-3% at T < 100 K for 10-20 mg powders, and ~ 5% for 5 mg powders).

The accuracy was highest for cp measurements on single-crystals and sintered-powder. For these, PPMS heat capacities were in excellent agreement with comparable low-TAC data (deviating from these by a maximum of 0.5 ± 0.8% in the temperature range 100–300 K). Heat capacity measurements on sealed powders did not achieve such a high degree of accuracy, but were systematically lower than low-TAC data by 1-2%. Reference entropies were reproduced with a relative error of ≤ 0.5% using single-crystal and sintered-powder samples, and were 1-2% too low for sealed-powder samples.

Our measurements demonstrate that the PPMS-calorimeter is a promising new tool for obtaining low-temperature cp-data and calorimetrically determined standard entropies for mg-sized mineralogical samples which are only available in limited amounts.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.