MECHANICAL AND DIELECTRIC ENERGY-LOSS RELATED TO VISCOUS MOTION AND FREEZING OF DOMAIN-WALLS

Three dielectric loss (D) and/or three mechanical loss (Q(-1)) peaks ( P-1,P-2,P-3) and corresponding susceptibilities for ferroelectric KDP and TGS, and ferroelastic LNPP crystal and Cu-Al-Zn-Ni alloy have been investigated in the kHz range. P-1 and P-2 almost overlap for first o rder phase transitions. P-1, a very narrow peak, is attributed to the dynamic domains due to fluctuations near T-C. P-2 is recognized to be related to domain walls (DWs). The formulas of Q(-1) and D caused by t he viscous motion of DWs are derived, being fairly coincident with the experimental data of P-2. The viscous coefficient, pinning force cons tant of DW and the spontaneous shear strain have been calculated for C u-Al-Zn-Ni. The susceptibility, epsilon' or Delta J/J, always shows a high plateau below T-C and drops down rapidly nearly consistent with t he low temperature side of P-3 peak for poly-domain TGS, KDP and Cu-Al -Zn-Ni. P-3 is thought to originate from the freezing of DWs of high d ensity due to a collective pinning of randomly distributed defects, si milar to the pinned-vortex glass model suggested for high T-C supercon ductors.