Calorimetric determination of the enthalpy of formation of InN and comparison with AlN and GaN
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F. Tessier UMR CNRS 6512 “Verres et Ce´ramiques,” Institut de Chimie de Rennes, Universite´ de Rennes 1, F-35042 Rennes Cedex, France
A. Navrotskya) Department of Chemical Engineering and Materials Science, University of California at Davis, Thermochemistry Facility, One Shields Avenue, Davis, California 95616
R. Marchand UMR CNRS 6512 “Verres et Ce´ramiques,” Institut de Chimie de Rennes, Universite´ de Rennes 1, F-35042 Rennes Cedex, France (Received 23 March 2001; accepted 18 July 2001)
The standard enthalpy of formation of InN at 298 K has been determined using high-temperature oxidative drop solution calorimetry in a molten sodium molybdate solvent at 975 K. Calorimetric measurements were performed on six InN samples with varying nitrogen contents. The samples were characterized using x-ray diffraction, chemical analysis, electron microprobe analysis, and Brunauer–Emmett–Teller surface area measurement. The variation of the enthalpy of drop solution (kJ/g) with nitrogen content is approximately linear. The data, when extrapolated to stoichiometric InN, yield a standard enthalpy of formation from the elements of −28.6 ± 9.2 kJ/mol. The relatively large error results from the deviation of individual points from the straight line rather than uncertainties in each set of data for a given sample. This new directly measured enthalpy of formation is in good agreement with the old combustion calorimetric result by Hahn and Juza (1940). However, this calorimetric enthalpy of formation is significantly different from the enthalpy of formation values derived from the temperature dependence of the apparent decomposition pressure of nitrogen over InN. A literature survey of the enthalpies of formation of III–N nitride compounds is presented.
I. INTRODUCTION
Nitrides of composition AN (A ⳱ Al, Ga, and In), III–N, represent important optoelectronic materials with semiconductor applications such as quantum wells, lasers, display devices, and storage devices.1 Being at the forefront of electronics materials research, they are prepared in the form of thin films, synthesized as nanocrystalline and/or amorphous materials and grown as single crystals.2–14 Research focuses toward synthesizing III–N alloys to achieve better performance in various applications. However, the determination of thermochemical data, essential for understanding phase stability and growth issues, is often neglected. Oxidative drop solution a)
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J. Mater. Res., Vol. 16, No. 10, Oct 2001 Downloaded: 15 Mar 2015
calorimetry in a molten salt solvent at high temperature has been shown to be a general method to determine the heat of formation of nitrides and oxynitrides.15 Several studies were performed on the energetics of binary and ternary transition metal nitrides,16–21 Si3N4 and sialon systems,22–25 the Zr–O–N,26 Y–Zr–O–N, Ca–Zr–O–N, and Mg–Zr–O–N systems, 27 and nitridophosphate PON28 and Li–Na–P–O–N glasses.29 Recently, we resolved a major d
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