MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
Standard Gibbs Energy of Formation of Zn8La Determined by Solution Calorimetry and Measurement of Heat Capacity from Near Absolute Zero Kelvin
Masao MorishitaHiroaki YamamotoKohei TsubokiYasutomo Matsumoto
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2006 Volume 47 Issue 6 Pages 1555-1559

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Abstract

The thermodynamic properties of Zn8La were investigated by calorimetry. The standard entropy of formation at 298 K, ΔfS298°, was determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, ΔfH298°, was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, ΔfG298°, was determined from these data. The results obtained were as follows: ΔfH298°(Zn8La)/kJ·mol−1 = −297.18±18; ΔfS298°(Zn8La)/J·mol−1·K−1 = −25.02±3.60; ΔfG298°(Zn8La)/kJ·mol−1 = −289.71±18. The coefficient, γ, of the electronic term contributing to the heat capacity of Zn8La was small, indicating that decrease of the density of states for 4f component of the lanthanum atom in the vicinity of EF.

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© 2006 The Japan Institute of Metals and Materials
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