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Titre du document / Document title

Refinement of thermodynamic data for LaMnO3

Auteur(s) / Author(s)

JACOB K. T. (1) ; ATTALURI Mrinalini (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Department of Metallurgy, Indian Institute of Science, Bangalore-560012, INDE

Résumé / Abstract

The standard Gibbs energy of formation of LaMnO3 has been measured in the temperature range from 900 to 1400 K using a solid-state cell incorporating a buffer electrode. The oxygen potential corresponding to the three-phase mixture MnO + La2O3 + LaMnO3 has been measured using pure oxygen gas at 0.1 MPa as the reference electrode, and yttria-stabilized zirconia as the solid electrolyte. The buffer electrode prevented polarization of the three-phase electrode and ensured accurate data. The measured oxygen chemical potential corresponding to the decomposition of LaMnO3 to MnO, La2O3 and O2 gas is in fair agreement (±6 kJ mol1) with most data available in the literature and can be represented by the equation, ΔμO2/J mol-1 (±520) = -583160 + 170.55 (T/K) Combining this with available information on oxygen potential variation with the non-stoichiometric parameter δ, the standard Gibbs free energy of formation of LaMnO3 from MnO, La2O3 and O2 was evaluated. The correction for non-stoichiometry was ∼ 1.6(±0.7) kJ mol-1. The heat capacity of LaMnO3 has been measured by a differential scanning calorimeter from 400 to 1060 K. Information on low-temperature heat capacity available in the literature was joined smoothly with the high-temperature data to evaluate the standard entropy of LaMnO3 at 298.15 K as 116.68 J mol-1 K-1. The third-law analysis of the Gibbs energy values obtained in this study yields a value of - 155.93 (±0.8) kJ mol-1 for the standard enthalpy of formation of LaMnO3 from MnO, La2O3 and O2 at 298.15 K. This value provides a critical test of calorimetric data on enthalpy of formation of LaMnO3. A consistent set of thermodynamic data for LaMnO3 is presented from 298.15 to 1400 K based on the results obtained in this study and other supporting information in the literature.

Revue / Journal Title

Journal of material chemistry    ISSN  0959-9428 

Source / Source

2003, vol. 13, no4, pp. 934-942 [9 page(s) (article)] (34 ref.)

Langue / Language

Anglais

Editeur / Publisher

Royal Society of Chemistry, Cambridge, ROYAUME-UNI  (1991) (Revue)

Mots-clés anglais / English Keywords

Ternary system

;

Phase equilibrium

;

Phase diagram

;

Manganese Oxides

;

Lanthanum Oxides

;

Ternary compound

;

Gibbs free energy

;

Heat of formation

;

Thermodynamic properties

;

Experimental study

;

Mots-clés français / French Keywords

La Mn O

;

LaMnO3

;

Système ternaire

;

Equilibre phase

;

Diagramme phase

;

Manganèse Oxyde

;

Lanthane Oxyde

;

Composé ternaire

;

Energie libre Gibbs

;

Chaleur formation

;

Propriété thermodynamique

;

Etude expérimentale

;

Mots-clés espagnols / Spanish Keywords

Sistema ternario

;

Equilibrio fase

;

Diagrama fase

;

Manganeso Óxido

;

Lantano Óxido

;

Compuesto ternario

;

Energía libre Gibbs

;

Calor formación

;

Propiedad termodinámica

;

Estudio experimental

;

Localisation / Location

INIST-CNRS, Cote INIST : 22603, 35400011115087.0570

Nº notice refdoc (ud4) : 14794879



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