Thermodynamic properties of MgGa2O4 and phase relations in the system Mg-Ga-O

Jacob, KT and Sivakumar, Shivesh (2019) Thermodynamic properties of MgGa2O4 and phase relations in the system Mg-Ga-O. In: JOURNAL OF ALLOYS AND COMPOUNDS, 775 . pp. 1357-1364.

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Abstract

Materials based on MgGa2O4 find use in microwave dielectrics, optoelectronics, spintronics and solid electrolytes for high-temperature fuel cells. For designing optimum processing conditions and evaluating interactions with other materials and environments, thermodynamic data and appropriate phase diagrams are required. As part of a larger systematic study on spinels with functional applications, thermodynamic properties of MgGa2O4 are determined in the temperature range from 875 to 1325 K using an electrochemical cell incorporating yttria-stabilized zirconia as the solid electrolyte. The Gibbs energy of formation of MgGa(2)O(4 )from its constituent binary oxides MgO with halite structure and beta-Ga2O3 with monoclinic structure is obtained: Delta G(f(ox))(0 )(+/- 135)/J mol(-1)= -39868-8.742 (T/K). The heat capacity of MgGa2O4 in the temperature range from 310 to 1200 K is measured by DSC. Both positive and negative deviations from Neumann-Kopp rule are seen in different temperature ranges. Derived from these measurements are the standard enthalpy of formation and standard entropy of MgGa2O4 at 298.15 K. The isothermal section of the phase diagram of the system Mg-Ga-O and oxygen potential-composition diagram at 1200 K are computed from thermodynamic data. (C) 2018 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	JOURNAL OF ALLOYS AND COMPOUNDS
Publisher:	ELSEVIER SCIENCE SA
Additional Information:	Copyright of this article belong to ELSEVIER SCIENCE SA
Keywords:	Heat capacity; Gibbs energy of formation; Enthalpy; Entropy; Oxygen potential diagram; Magnesium gallate
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	23 Dec 2018 06:52
Last Modified:	23 Dec 2018 06:52
URI:	http://eprints.iisc.ac.in/id/eprint/61272

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