A multi-Debye relaxation model that is based upon the Boltzmann superposition principle has been used to determine the frequency-dispersion behavior of Pb(Mg 1/3 -Nb 2/3 )O 3 (PMN) and Pb 0.88 La 0.08 (Zr 0.65 Ti 0.35 )O 3 (PLZT 8/65/35) relaxor ferroelectrics. For PMN, relaxation times on the order of seconds contribute to the dispersive character of the dielectric properties. A defect-relaxation mechanism that involves Mg cation hopping in a structure that is composed of interpenetrating 〈111〉 chains of ordered Pb(Mg 1/2 Nb 1/2 )O 3 is proposed for PMN. Motion of the Mg cations results in destruction and reconstruction of these ordered chains, which contributes to the dispersive character of PMN.

A high damping Cu-Mn alloy with a nominal composition of 48Cu-48Mn-1.5Al-0.27Si-0.072Sn-0.028C-0.05Er (all compositions in wt pct) was studied to determine the mechanism of the loss of damping capacity during room-temperature storage. In this study, it was found that an Er-modified alloy sample that was artificially aged for 16 hours at 400 ЊC was stable even after 68 weeks of room-temperature storage. However, a loss of damping capacity was exhibited in the same material when aged to produce an underaged or peakaged condition. The decrease in damping capacity was found to be thermally activated with at least three relaxation processes. Each of the three relaxation processes appear to be related to the diffusion of carbon within the Mn-rich regions and a single activation energy of 0.970 ‫ע‬ 0.05 eV was used to model these processes. Rapid loss of damping capacity was observed in the same alloy when doped with excess carbon. After 3 weeks of storage at room temperature, the damping of the carbon-doped material, artificially aged at 400 ЊC for 4 hours, was reduced to one-third of its initial damping capacity.