“…Some of the anomalies were shown to be related to the oxygen content of the materials. 17,18 In RBa 2 Cu 3 O 7−δ (R = rare earth), the elastic anomalies between 200-250 K have been associated with oxygen ordering in the Cu-O chains [19][20][21] and related phase diagrams have been computed for Y-123 22,23 to explain the phenomena.…”
Ultrasonic longitudinal and shear velocities propagated at 7-10 MHz in bulk Tl 2 Ba 2 Ca 2 Cu 3 O 10 have been measured between 80 K and 300 K. Shear velocity measurements revealed a pronounced slope discontinuity of 421 ppm/K at around 160 K. A similar slope change was not observed in the longitudinal mode. The slope change around 160 K for the shear mode is suggested to be attributed to some form of correlated Tl and O(4) orderings in the material. PACS Number(s): 74.2.Fq, 74.25.L and 62.20.Dc
“…Some of the anomalies were shown to be related to the oxygen content of the materials. 17,18 In RBa 2 Cu 3 O 7−δ (R = rare earth), the elastic anomalies between 200-250 K have been associated with oxygen ordering in the Cu-O chains [19][20][21] and related phase diagrams have been computed for Y-123 22,23 to explain the phenomena.…”
Ultrasonic longitudinal and shear velocities propagated at 7-10 MHz in bulk Tl 2 Ba 2 Ca 2 Cu 3 O 10 have been measured between 80 K and 300 K. Shear velocity measurements revealed a pronounced slope discontinuity of 421 ppm/K at around 160 K. A similar slope change was not observed in the longitudinal mode. The slope change around 160 K for the shear mode is suggested to be attributed to some form of correlated Tl and O(4) orderings in the material. PACS Number(s): 74.2.Fq, 74.25.L and 62.20.Dc
“…Second, if the structure of the material also is inhomogeneous, for example, containing twins, grain boundaries, a stress field will be established in various areas of the phase transformation, and possibly will obstruct or enhance the occurrence of the phase transformation. Despite many reports on the SIOR phase transformation, [34][35][36][37][38][39][40][41][42] the values of changes in specific heat, the thermal-expansion coefficients, and the elastic compliances during phase transformation are seldom reported. The exceptions are Nagel et al's 34 measurements of the thermal-expansion coefficients in untwinned single crystals, and the work of Cankurtaran and his co-workers, 37,38 who assessed the changes in elastic stiffness in an isotropic polycrystal sample.…”
Section: Discussionmentioning
confidence: 99%
“…11,[13][14][15][16]18,22,32,33 However, another phase transformation, occurring about 220-280 K, which relates to the discontinuous change of material's lattice constants, 34 specific heat, 35,36 elastic stiffnesses, 37-40 electrical resistivity, 41 and dielectric constant, 42 has only been revealed experimentally. Although most experimenters deemed that this phase transformation is related to the reordering of oxygen atoms, [34][35][36][37][38][39][40][41] it has no theoretical explanation until now. In this paper, we suggest a thermodynamic framework and lattice distortion mechanism to explain this oxygen-reordering process and then discuss some thermodynamic response functions on either side of the critical temperature of the phase transformation.…”
We propose a thermodynamic model to explain an unusual phase transformation occurring near room temperature in YBa 2 Cu 3 O 6+x that greatly affects properties of the superconductor. Based on our model, the material's thermodynamic response functions, specific heat, thermal-expansion coefficient, and elastic compliances are deduced at the critical temperature of the phase transformation. We discuss the change of critical temperature with stress, and analyze the anomaly of specific heat in critical temperature of the phase transformation.
“…Similarly, the measured compressional sound velocities in YBa 2 Cu 3 O 7−δ measured by Toulouse et al . 33 clearly plateau for 90K.Figure 2Elastic modulus of superconductors. Circles show vs of Bi 2 Sr 2 CaCu 2 O 8+γ .…”
Section: Temperature Independence Of Young’s Modulus Of Superconductomentioning
It is shown that in the ergodic regime, the temperature dependence of Young’s modulus is solely determined by the magnetic properties of a material. For the large class of materials with paramagnetic or diamagnetic response, simple functional forms of the temperature derivative of Young’s modulus are derived and compared with experimental data and empirical results. Superconducting materials in the Meissner phase are ideal diamagnets. As such, they display remarkable elastic properties. Constant diamagnetic susceptibility gives rise to a temperature independent elastic modulus for ceramic and single crystalline superconductors alike. The thermodynamic approach established in this report, paves the way to tailor elastic material parameters through the design of magnetic properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
