Mechanical and dielectric dissipation related to phase transitions

Abstract

(1) First Order Phase Transition There always appear two dielectric loss and/or two mechanical dissipation peaks (P2 and P3 ) related to domain walls in many martensitic and ferroic materials. The P2 near Tc (or Ms ) originates from first-order phase transition or phase-like transition and shows static hysteresis character, but in a certain frequency range (kHz) manifests relaxation behavior, with t—t 0exp[− B/(Tc—T)]. The transient componant of P2 is also reviewed. (2) Glass Transition The peak P 3 at kHz often appears near a freezing temperature Tf as in KDP, TGS and occasionally in Mn-Cu at Hz, with T = T 0exp[U/(T- Tf)], a Vogel-Fulcher relation, showing a “Transition” type of glass-transition of domain wall. Whereas the glass-transition in C60 crystal obeys the Arrhenius relation, exibiting “Kinetic” type of glass-transition. (3) Flux Melting The peak just below Tc was measured for melt-textured YBa2Cu3O7 +δ superconductors in an applied magnetic field and various frequencies. The peak hight satisfies the power law Q −1 ∝ ω −n (1 < n < 2), being explained by the melting and viscous motion of flux.