An ultrasonic study of oxygen related structures in Nd123 between 80 and 400 K

This paper reports on an ultrasonic study at 130 kHz region in melt-texture d Nd123, i.e. NdBa2Cu3O7-delta with different oxygen levels, i.e. delta = 0 , 0.2, 0.4, 0.6, 1. Three ultrasonic attenuation peaks were identified, whi ch were related to oxygen levels in the material. An ultrasonic attenuation peak in the 360 K region was found at higher oxygen levels, i.e. delta = 0 .2, 0.4, and appeared to be a characteristic of the orthorhombic phase of t he material. An ultrasonic attenuation peak in the 160 K region occurred at lower oxygen levels, i.e. delta = 0.4, 0.6, while a peak close to 320 K wa s found in deoxygenated Nd123. All ultrasonic attenuation peaks showed the characteristics of structural changes. This proposal is supported by ultras onic velocity measurements which displayed discontinuities at the correspon ding temperatures. (C) 1999 Elsevier Science S.A. All rights reserved.