Elastic properties of polycrystalline YBa_2Cu_3O_7: Evidence for granularity induced martensitic behavior

TL;DR

This study investigates the elastic properties of polycrystalline YBa_2Cu_3O_7, revealing hysteretic ultrasonic attenuation indicative of granularity-induced martensitic-like behavior above the superconducting transition.

Contribution

It provides evidence for granularity-induced martensitic behavior in YBa_2Cu_3O_7 through ultrasonic measurements, highlighting a new aspect of its low-temperature elastic properties.

Findings

Hysteretic ultrasonic attenuation observed

Evidence of martensitic-like phase above T_C

Granularity influences elastic behavior

Abstract

In this work we present the study of the elastic properties of polycrystalline samples of superconducting YBa_2Cu_3O_7 prepared by the sol-gel method. The quality of all samples was checked by x-ray diffraction and scanning electronic microscopy while their physical properties were verified by transport and magnetic measurements. The elastic study was performed using the standard pulse-echo technique through measuring the phase velocity and the attenuation of ultrasonic waves (in the range of a few MHz) as a function of temperature. We have focused this study on the low temperatures interval (T < 200K). The obtained results show a strong hysteretic behavior in the ultrasonic attenuation (in addition to usually observed hysteretic behavior for the velocity) which strongly supports the existence of a martensitic-like phase above the superconducting critical temperature T_C. We argue that this peculiar behavior can be attributed to the granularity present in the samples.