Precision calorimetry at low temperatures

Anomalies of the electronic heat capacity of thulium cuprates in the pseudogap phase region

“…Heat capacity of empty calorimeter was measured in the temperature range 6 -310 K. The accuracy of the calorimetric results was tested using the standard reference sample -benzoic acid. Our results agree with reliable data for benzoic acid taken from the literature [22][23][24] within the limits of ±2 % over the temperature range 6 -10 K, 0.5 % for 10 -30 K, 0.2 % for 30 -60 K, and 0.1 % above 60 K. During the measurements, temperature increase at the heat pulse was 1 to 2 K at T < 30 K and 3 -5 K over the temperature range 30 -300 K. The average deviation of the experimental values from the smoothed curve was about 0.02 % at temperatures 100 -300 K. The deviation increased with decreasing temperature, growing up to 1 % at 10 K. A total of 300 -400 experimental points were performed for each sample.…”

Low-Temperature Heat Capacity and Thermodynamic Functions of Tetrameric Cobalt(II) Acetylacetonate

“…A sample of mass 7.525 ± 0.001 g (in vacuum) of benzoic acid was utilized. The deviations of our data and the results of others 22,23 from the reference data C r (T) (Rybkin et al 21 at T < 273 K and Sabbah et al 22 at T > 273 K) are indicated in Figure 3. Data from Rybkin et al 21 were converted from IPTS-68 to ITS-90 (Table S2 in the Supporting Information).…”

The low temperature heat capacity of Li2Mo0.05W0.95O4

“…The obtained data reliability is confirmed by heat capacity measurements of a standard substance (benzoic acid), characterizing the uncertainty of setup calibration. The deviation from standard data [15] in the temperature range from 80 to 300 K is 0.15%. The calorimetric ampoule temperature is measured with a platinum resistance thermometer; the standard temperature uncertainty corresponds to 0.01 K. A dismountable nickel calorimetric ampoule was filled by a set of Li2Mo0.05W0.95O4 crystals with a typical size of about 5 mm in diameter and vacuumed at room temperature.…”

“…Their values under standard conditions (T = 298.15 K, p = 0.1 MPa) were as follows: 15 𝐻 𝑚 ° = 21.79 ± 0.11 kJ mol −1 , Δ 0 298.15 𝐺 𝑚 ° = −19.4 ± 0.7 kJ mol −1 K −1 . An expanded combined uncertainty (confidence interval of 95%) of thermodynamic function values, which is due to the scatter of experimental points, the uncertainty in the calibration of the experimental setup, and the uncertainty in the method of extrapolating the heat capacity to zero temperatures, is given.…”