INTERNAL-FRICTION NEAR THE ORTHORHOMBIC-TO-TETRAGONAL PHASE-TRANSITION IN YB2CU3O7-X AT 80-200KHZ

The internal friction and compliance of YBa2Cu3O7-x are measured at te mperatures from 300 to 1050K using a LiNbO3 composite oscillator techn ique. An anelastic relaxation due to oxygen movement at 80-200kHz is o bserved to be associated with the orthorhombic-to-tetragonal (O-T) pha se transition in YBa2Cu3O7-x at 850-900 K. By careful fitting for the measured internal friction against temperature, we provide data on the relaxation time and peak temperature in the highest frequency region for a Linear Arrhenius plot that extends over 7 orders of magnitude.