The normal-state anomalous behaviours studied by internal friction of partially Sr-substituted Y123 in the underdoped range

Abstract

The internal friction of partially Sr-substituted Y(Ba1−xSrx)2Cu3O7−δ (x = 0.1, 0.2, and 0.5) ceramics with different oxygen content was measured using the vibrating-reed method from liquid nitrogen temperature to room temperature at kilohertz frequencies. A broad mechanical-energy dissipation peak and a sharp one were observed around 220 K. The position of the broad internal-friction peak does not show a systematic change with the oxygen content, and its intensity decreases after depleting a great amount of oxygen. For the sample with high oxygen concentration, another broad peak of lower intensity appeared around 150 K, which might relate to a microstructure change. At the same time, we have not found any anomalous behaviour of internal friction between 90 and 200 K for the sample with lower oxygen content, where the opening of a pseudogap for underdoped YBa2Cu3O7−δ has been observed in many other experiments. Our results provide more information about the normal-state properties of high-temperature superconductors.