Relaxations in mixed alkali metaphosphate glass

Abstract

A study of the materials response to time-dependent mechanical and electrical perturbations was performed on a mixed alkali, sodium and lithium, metaphosphate glass over a range of overlapping frequencies. The characteristic timescale that characterizes the mechanical relaxations, τ μ , was observed to be two orders of magnitude slower than the characteristic response, τ σ , of the system to electrical perturbations. This is unlike the situation in single alkali glasses where τ μ and τ σ are equivalent. Interestingly, it was also noted that the breadth of the distribution of relaxation times that characterize the response of the mixed mobile ion system is slightly narrower than that of the single alkali (Li) metaphosphate. A comparison of the characteristic timescales, τ 1, that describes the nuclear magnetic resonance spin-lattice relaxation time response revealed that τ 1 is comparable to τ σ . This is also by contrast with the single alkali case where τ σ is approximately one order of magnitude faster than τ 1. However, as observed in single alkali glasses, the breadth of the distribution of relaxation times that characterize the loss processes of the mechanical response is considerably larger than that of the electrical response.