Heat capacity, third-law entropy, and low-temperature physical behavior of bulk hematite (α-Fe 2O 3)

• Published in: The Journal of chemical thermodynamics Vol. 42; no. 9; pp. 1136 - 1141
• Main Authors: Snow, Claine L., Shi, Quan, Boerio-Goates, Juliana, Woodfield, Brian F.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2010; Elsevier
• Subjects: Chemical thermodynamics; Chemistry; Elements, mineral and organic compounds; Exact sciences and technology; Fe 2O 3; General and physical chemistry; Heat capacity; Hematite; Morin transition; PPMS; Thermodynamic properties; Hematite; Heat capacity; Fe 2O 3; PPMS; Morin transition; Temperature effect; Entropy; Operating conditions; Magnetic transition; O; Thermal properties; Measuring system; Iron III Oxides; Thermodynamic properties; Fe
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2010.04.010

The constant pressure heat capacity of a bulk hematite powder was measured using a Quantum Design physical properties measurement system (PPMS). The results of two series showed good precision and agreed well with measurements reported by Westrum and Grønvold. The standard molar entropy at T = 298.15 K was calculated to be (87.32 ± 2) J · mol −1 · K −1 for Series 1 and (87.27 ± 2) J · mol −1 · K −1 for Series 2, which are in good agreement with the value of (87.40 ± 0.2) J · mol −1 · K −1 (originally 20.889 cal · deg −1 · mole −1) calculated by Westrum and Grønvold. No anomaly was observed for the Morin transition, and theoretical fits below T = 15 K required a ferromagnetic T 3/2 term.