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Internal friction measurements on polycrystalline YBa2Cu3O7−x

✍ Scribed by M. Weller; H. Jaeger; G. Kaiser; K. Schulze

Publisher
Elsevier Science
Year
1989
Tongue
English
Weight
147 KB
Volume
162-164
Category
Article
ISSN
0921-4534

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✦ Synopsis

The internal friction (IF) of polycrystalline YBa~-'u307-x was studied from 4 to 300K for frequencies between 2 and 19 I-~ The samples were ]prepared by the standard solid state reaction method. The oxygen content was varied by annealing the samples in atr at various temperatures and subsequent cooling in flowing Ar or 02. For YBa2C"u306.9 two closely related and reproducible IF peaks appear: peak A at 68 K and peak B at 87 K (f = 8 Hz). Both peaks are shifted to higher temperatures with increasing frequency as expected for thermally activated (stress induced) reorientation of atomic defects. The parameters for the temperature dependence of the relaxation time, r = r(®) = exp(H/kT), were determined as HA = 0.15 eV, r^(00) = 10 "13 s; FIB = 0.17 eV, rB(®) = 10 "t2 s. We assume that peaks A and B are connected with jumps of oxygen vacancies. The influence of oxygen content will be discussed in this context. Other peaks at about 40 to 50 K do not shift with frequency and are probably due to phase transitions.

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