On the Possibility of Forming Complexes with the Participation of O2– Ions in Melts and Glasses of the Na2O–SiO2–Cu2O System

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In this Subject: <a title="Chemical Engineering" href="/content/subcat?j_subject=165&j_availability=">Chemical Engineering
By this author: Borisova N.V. ;&nbsp; Konakov V.G. ;&nbsp; Kostyreva T.G. ;&nbsp; Shultz M.M.

Authors: Borisova N.V.; Konakov V.G.; Kostyreva T.G.; Shultz M.M.

Source: Glass Physics and Chemistry, Volume 29, Number 1, January 2003 , pp. 28-34(7)

Publisher: MAIK Nauka/Interperiodica

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Abstract:

The structural role of copper ions in melts (glasses) of the Na₂O–SiO₂–Cu₂O–CuO system is analyzed in the framework of the acid–base concept with due regard for the geometric (the radius ratio for Cu²⁽¹⁾⁺ and O^2– ions) and energy (the mean enthalpies of the Cu²⁽¹⁾⁺–O bonds) factors. It is demonstrated that copper ions in the structure fulfill the function of modifier cations. In these melts, the Cu¹⁺–Cu²⁺ redox equilibrium can be described without regard for the formation of [Cu²⁽¹⁾⁺O_4/2 ]^2(3)– ionic complexes (which could be incorporated into the structure of silicon–oxygen anions) and [Cu²⁺O_b/k ]^{2 – b/k} polyhedra providing the interaction between Cu²⁺ ions and anions. The influence of the formation of these polyhedra on the redox equilibrium is considered within the formalism of chemical thermodynamics. The composition dependence of the oxygen ion exponent pO is measured by an electromotive force (emf) technique. The ratio between the numbers of copper atoms with different valences is determined by chemical analysis. The experimental data obtained are in agreement with the theoretical inferences.