Electrical and Mechanical Relaxations in a Mixed‐Alkali Silicate Glass

Electrical relaxation measurements from 0.04 Hz to 2.5 MHz between 80° and 283°C and mechanical relaxation measurements from 120 to 3600 Hz between ‐44° and 305°C were conducted for 0.5Na ₂ O·0.5K ₂ O·3SiO ₂ glass. The average time constant for the electric‐field relaxation, which is controlled by the diffusion of the more mobile Na ⁺ ion, was smaller by a factor of ∼30 to 50 than that for the mechanical relaxation associated with the mixed‐alkali internal friction peak. This result supports the theory of Day and co‐workers that the time constant for mixed‐alkali mechanical relaxation is controlled by the less mobile alkali ion (K ⁺ ). The results indicate that a distinct mixed‐alkali electrical relaxation analogous to mixed‐alkali mechanical relaxation is not observed because the electric field in the glass decays rapidly to zero via diffusion of the more mobile cation, rather than because the mixed‐alkali mechanical‐relaxation mechanism is inherently electrically inactive.