Journal of Chemical Thermodynamics, Vol.42, No.9, 1136-1141, 2010
Heat capacity, third-law entropy, and low-temperature physical behavior of bulk hematite (alpha-Fe2O3)
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 Crony Id. 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 Gronvold. No anomaly was observed for the Morin transition, and theoretical fits below T = 15 K required a ferromagnetic T-3/2 term. (C) 2010 Elsevier Ltd. All rights reserved.