# Refinement of thermodynamic data on GaN

Jacob, KT and Singh, Shwetank and Waseda, Y (2007) Refinement of thermodynamic data on GaN. In: Journal of Material Research, 22 (12). pp. 3475-3483.

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## Abstract

Although GaN is one of the important electronic materials of this decade, thermodynamic data for this compound are not known with sufficient reliability. The limited information available is not internally consistent. Measured in this study are high-temperature heat capacities using a differential scanning calorimeter and Gibbs energies of formation employing a solid-state electrochemical technique. The solid-state cell was based on single-crystal $CaF_2$ as the electrolyte and $Ca_3N_2$ as the auxiliary electrode to convert the nitrogen chemical potential established by the equilibrium between Ga and GaN into an equivalent fluorine potential. The heat capacity of GaN at ambient pressure can be represented by the equation: $C^o_P / J mol^{-1}$ $K^{-1} = 74.424 − 0.00106T$ + $(46720/T^2)$ − $(685.9/T^{0.5})$, in the temperature range from 350 to 1075 K. The standard Gibbs energy of formation of GaN in the range from 875 to 1125 K can be expressed as: $\Delta fG^o/ J mol^{-1}$ (\pm465) = −128,749 + 115.029 T. This corresponds to a decomposition temperature of 1119 \pm 4 K for GaN in pure nitrogen at standard pressure. On the basis of these new measurements and a critical assessment of information that is available in the literature, a refined set of data for GaN in the temperature range from 298.15 to 1400 K is presented.

Item Type: Journal Article Copyright of this article belongs to Materials Research Society. Division of Chemical Sciences > Materials Research Centre 06 Jun 2008 19 Sep 2010 04:45 http://eprints.iisc.ernet.in/id/eprint/14222