Mixed Alkaline Effect in Antimony-Based Glasses

Resumo

The mixed alkaline effect (MAE) is a well-known anomaly in glasses. It results in a non-linear response of various physical properties on mixing of alkali ions in the glass. In this paper, the MAE is studied in antimony oxides based glasses 60Sb₂O₃–20MoO₃–(20 – x)Li₂O–xNa₂O and 60Sb₂O₃–20MoO₃–(20 – x)Li₂O–xK₂O (in mol %). The influence of Na/Li and K/Li ratios on ionic AC and DC conductivities, and T_g is presented. Dependences of T_g on x, in both types of glasses, have typical minima at x ≅ 10, it means that the minima take place at approximately equal concentrations of both mixed alkali ions. The minimum for K₂O containing glasses is deeper, probably due to a larger difference between ionic radii of K⁺ and Li⁺ ions. In glasses with one type of alkali ion, T_g decreases in the sequence: K → Li → Na. Temperature dependences of the DC conductivity obey Arrhenius-like relation. The conductivity steeply decreases with increasing Na or K content due to the larger ionic radius of both ions comparing to that of Li ions. At the same time, the conduction activation energy goes through a flat maximum at x = 15 (1.21 eV) for Na₂O modifier and at x = 5 (1.16 eV), for K₂O modifier. In antimony oxide based glasses, Li⁺, Na⁺, and K⁺ ions are modifiers and dominant charge-carriers. Due to larger ionic radii of Na⁺, and K⁺, the decrease of the conductivity after their addition is reasonable.