Trends in the Stability of Ternary Oxides: Systems M-Pb-O (M = Ca, Sr, Ba)
| Autor: | K. T. Jacob, K. P. Jayadevan |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2000 |
| Předmět: |
Technology
Materials science Oxide chemistry.chemical_element Chemicals: Manufacture use etc TP1-1185 Oxygen Metal chemistry.chemical_compound Oxidation state Phase (matter) General Materials Science Physical and Theoretical Chemistry Phase diagram Materials Research Centre Chemical technology Materials Engineering (formerly Metallurgy) TP200-248 Condensed Matter Physics chemistry Mechanics of Materials visual_art visual_art.visual_art_medium Physical chemistry Chemical stability Ternary operation |
| Zdroj: | High Temperature Materials and Processes, Vol 19, Iss 6, Pp 399-408 (2000) Scopus-Elsevier |
| ISSN: | 2191-0324 0334-6455 |
| Popis: | Recent experimental investigations of phase equilibria and thermodynamic properties of the systems M-Pb-O, where M = Ca, Sr or Ba, indicate a regular increase in thermodynamic stability of ternary oxides, MPbO3 and M2PbO4, with increasing basicity of the oxide of the alkaline-earth metal. Number of stable interoxide compounds at 1100 K in the systems M-Pb-O (M = Mg, Ca, Sr, Ba) increases in unit increments from Mg to Ba. In this paper, experimentally determined standard Gibbs energies of formation of M2PbO4 (M = Ca, Sr, Ba) and MPbO3 (M = Sr, Ba) from their component binary monoxides and oxygen gas are combined with an estimated value for CaPbO3 to delineate systematic trends in thermodynamic stability of the ternary oxides. The trends are interpreted using concepts of tolerance factor and acid-base interactions. All the ternary oxides in these systems contain lead in the tetravalent state. The small Pb4+ ions polarize the surrounding oxygen ions and cause the formation of oxyanions which are acidic in character. Hence, the higher oxidation state of lead is stabilized in the presence of basic oxides of alkaline-earth group. A schematic subsolidus temperature-composition phase diagram is presented for the system BaO-PbO-O-2 to illustrate the change in oxidation states in binary and ternary oxides with temperature. |
| Databáze: | OpenAIRE |
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