Heat capacity of ferrosilite, Fe2Si2O6

Cemic, L. and Dachs, E. (2006) Heat capacity of ferrosilite, Fe2Si2O6 Physics and Chemistry of Minerals, 33 (7). pp. 457-464. DOI 10.1007/s00269-006-0090-1.

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Abstract

The heat capacity of synthetic ferrosilite, Fe2Si2O6, was measured between 2 and 820 K. The physical properties measurement system (PPMS, Quantum Design(R)) was used in the low-temperature region between 2 and 303 K. In the temperature region between 340 and 820 K measurements were performed using differential scanning calorimetry (DSC). The C-p data show two transitions, a sharp lambda-type at 38.7 K and a small shoulder near 9 K. The lambda-type transition can be related to collinear antiferromagnetic ordering of the Fe2+ spin moments and the shoulder at 10 K to a change from a collinear to a canted-spin structure or to a Schottky anomaly related to an electronic transition. The C-p data in the temperature region between 145 and 830 K are described by the polynomial C-p[J mol(-1) K-1] = 371.75 - 3219.2T(-1/2) - 15.199 x 10(5) T-2 + 2.070 x 10(7) T-3 The heat content [H-298 - H-0] and the standard molar entropy [S-298 - S-0] are 28.6 +/- 0.1 kJ mol(-1) and 186.5 +/- 0.5 J mol(-1) K-1, respectively. The vibrational part of the heat capacitiy was calculated using an elastic Debye temperature of 541 K. The results of the calculations are in good agreement with the maximum theoretical magnetic entropy of 26.8 J mol(-1) K-1 as calculated from the relationship 2* Rln5.

Document Type: Article
Keywords: ferrosilite heat capacity magnetic transition temperature orthopyroxenes calorimeter
Research affiliation: Kiel University
DOI etc.: 10.1007/s00269-006-0090-1
ISSN: 0342-1791
Date Deposited: 12 Jan 2012 05:41
Last Modified: 08 Oct 2012 10:23
URI: http://eprints.uni-kiel.de/id/eprint/15980

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