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Titre du document / Document title

Stability of Cu2Ln2O5 compounds: Comparison, assessment and systematics

Auteur(s) / Author(s)

JAYADEVAN K. P. (1) ; JACOB K. T. (1) ;

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

(1) Materials Research Center and Department of Metallurgy, Indian Institute of Science, Bangalore 560 012, INDE

Résumé / Abstract

Phase diagram studies show that at ambient pressure only one ternary oxide, Cu2Ln2O5, is stable in the ternary systems Cu-Ln-O (Ln = Tb, Dy, Ho, Er, Tm, Yb, Lu) at high temperatures. The crystal structure of Cu2Ln2O5 can be described as a zig-zag arrangement of one-dimensional Cu2O5 chains parallel to the a-axis with Ln atoms occupying distorted octahedral sites between these chains. Four sets of emf measurements on Gibbs energy of formation of Cu2Ln2O5 (Ln = Tb, Dy, Ho, Er, Tm, Yb, Lu; Y) from component binary oxides and one set of high-temperature solution calorimetric data on enthalpy of formation have been reported in the literature. Except for Cu2Y2O5, the measured values for the Gibbs energies of formation of all other Cu2Ln2O5 compounds fall in a narrow band (±1 kJ mol-1) and indicate a regular increase in stability with decreasing ionic radius of the lanthanide ion. The values for the second law enthalpy of formation, derived from the temperature dependence of emf obtained in different studies, show larger differences, as high as 25 kJ mol-1 for Cu2Tm2O5. Though associated with an uncertainty of ±4 kJ mol-1, the calorimetric measurements help to identify the best set of emf data. The trends in thermodynamic data correlate well with the global instability index (GII) based on the overall deviation from the valence sum rule. Low values for the index calculated from crystallographic information indicate higher stability. Higher values are indicative of the larger stress in the structure.

Revue / Journal Title

High-temperature materials and processes    ISSN  0334-6455   CODEN HTMPEF 

Source / Source

2000, vol. 19, no6, pp. 389-397 (24 ref.)

Langue / Language

Anglais

Editeur / Publisher

Freund, Tel Aviv, ISRAEL  (1984) (Revue)

Mots-clés anglais / English Keywords

Thermal stability

;

Thermal properties

;

Phase diagrams

;

Copper

;

Oxygen

;

Terbium

;

Ternary systems

;

Dysprosium

;

Holmium

;

Erbium

;

Crystal structure

;

Primitive cell

;

Experimental study

;

Thulium

;

Ytterbium

;

Mots-clés français / French Keywords

Stabilité thermique

;

Propriété thermique

;

Diagramme phase

;

Cuivre

;

Oxygène

;

Terbium

;

Système ternaire

;

Dysprosium

;

Holmium

;

Erbium

;

Structure cristalline

;

Maille primitive

;

Etude expérimentale

;

Thulium

;

Ytterbium

;

Système Cu O Tb

;

Système Cu Dy O

;

Mots-clés espagnols / Spanish Keywords

Celda primitiva

;

Localisation / Location

INIST-CNRS, Cote INIST : 16238, 35400009342370.0030

Nº notice refdoc (ud4) : 816672



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