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Thermodynamics of Silicon Nitride. I. Standard Molar Enthalpy of Formation Δ}fHmo at the Temperature 298.15K of α-Si3N4 and β-Si3N4

Published

Author(s)

P A. O'Hare, I. Tomaszkiewicz, C M. Beck, H. J. Seifert

Abstract

Fluorine bomb calorimetric measurements of the massic energy of the reaction: Si3N4 (cr, α- or β-) + 6F2(g) = 3SiF4(g) + 2N2(g) have shown that, within the combined uncertainties of the experiments, there is a negligible enthalpy difference between the α- and β- forms of Si3N4 at the temperature T= 298.15 K. The standard molar enthalpies of formation at T = 298.15 K have been determined: Δ}fHmo(α-Si3N4) = -(828.9 ± 3.4) kJ.mol-1, Δ}fHmo(β-Si3N4) = -(827.8 ± 2.5) kJ.mol-1. These results are approximately 40 kJ.mol-1 more negative than the recommended value given in the most recent authoritative compilation of chemical thermodynamic information for inorganic substances. The enthalpy difference between α and β forms, (1 ± 4) kJ.mol-1 at T = 298.15 K, is too small to be measured reliably by combustion calorimetry. It supports an earlier estimate of 1.25 kJ.mol-1 from a modelling study, and unpublished results from recent low-temperature calorimetric measurements.
Citation
Journal of Chemical Thermodynamics
Volume
31

Keywords

calorimetry, enthalpy of formation, enthalpy of transition, silicon nitride

Citation

O'Hare, P. , Tomaszkiewicz, I. , Beck, C. and Seifert, H. (1999), Thermodynamics of Silicon Nitride. I. Standard Molar Enthalpy of Formation {&#916;}<sub>f</sub>H<sub>m</sub><sup>o</sup> at the Temperature 298.15K of &#945;-Si<sub>3</sub>N<sub>4</sub> and &#946;-Si<sub>3</sub>N<sub>4</sub>, Journal of Chemical Thermodynamics (Accessed April 18, 2024)
Created December 31, 1998, Updated October 12, 2021