Application of the Rheovibron to inorganic glass problems I. The mixed alkali effect loss spectrum

A mechanical spectrometer with four decade frequency range has been used to characterize the isothermal mechanical loss spectrum of a mixed alkali silicate glass. The half width of the mechanical loss spectrum is very much greater than that for electrical relaxation at the same temperature despite the fact that both relaxations are due to alkali ion motion. It is suggested that the difference, which is also present in single alkali glasses is primarily a consequence of the fact that the mechanical relaxation is by nature a secondary relaxation (probably one of a sequence of broad secondary relaxations) while the electrical relaxation is a primary relaxation insofar as it is the process producing the largest of all changes of electrical modulus.