Anisotropic Thermal Diffusivity and Conductivity of YBCO(123) and YBCO(211) Mixed Crystals. I

Abstract

The anisotropic thermal diffusivity α of the highly c-axis-oriented Y–Ba–Cu–O bulk superconducting crystals has been measured quasi-simultaneously with the thermal conductivity κ. The estimated values of the specific heat C by use of α and κ values parallel and perpendicular to the c-direction agreed with each other. In these crystals prepared by the modified melt texture growth (MMTG) method, fine Y2BaCuO5 particles are dispersed in the YBa2Cu3O7- x superconducting matrix phase. Based on a simple model, the thermal diffusivity and the specific heat of the YBa2Cu3O7- x matrix phase are separated using independently measured data of a Y2BaCuO5 polycrystal. The influence of Y2BaCuO5 particles on the thermal properties of the mixed crystals is discussed.

Substitution effect of tetravalent and pentavalent elements on thermoelectric properties in In₂O₃-SnO₂ system

“…The electrical resistivity ρ(T) (or electrical conductivity σ(T)=1/ρ(T)) and Seebeck coefficient S(T) were simultaneously measured in the temperature range from 300 to 1273 K using an automated measuring system (Ozawa Science RZ2001i) and the thermoelectric power factor P=S 2 /ρ was calculated. The thermal conductivity κ(T) was measured by a laser flash method (Ulvac-Riko TC-7000) from 300 K to 1023 K. The  value below 300 K was also measured by steady-state heat flow method using home-made measuring system [15]. A dimensionless figure of merit ZT=S 2 T/ρκ was estimated using these values.…”

Macroscopic numerical evaluation of heat generation in a bulk high Tc superconductor during pulsed field magnetization

“…Distribution of the temperature in the HTS is obtained by the following heat diffusion equation: (14) where , are density, specific heat, and are heat conductivities along the -, -axes, and the -axis of the HTS as shown in Fig. 1 [15]. Therefore, in the analysis of the dynamic magnetization, the shielding current has the complex dependence on the dynamic field and on the temperature.…”

“…Flow resistivity is also evaluated with the Bardeen-Stephen (B-S) model [12] and the Tinkham model [13] in the analysis. Though the present simulation is not enough to evaluate real material perfectly, we have referred some physical parameters from [5], [14], and [15] and have improved the simulation code. The heat diffusion equation is solved to clarify the effect of the local heat generation in the bulk HTS during the pulsed-field magnetization.…”

Critical State Stability and Flux Jumps' Dynamics in a Single Crystal of YBa2Cu3O7-δ

“…Studies in the low temperature regime [8] reveal the in plane thermal conductivity at T = 1 K of about 10 −1 W/Km. At the temperature of 10 K, the reported in-plane thermal conductivity ranges form 1.6 W/Km [9] to about 6 W/Km [10]. In order to t these experimental data in the temperature range form 1 K to 20 K, we used a power function κ(T ) = 10 −1 T x , where x ≈ 1.2 for the data taken from [9] and x ≈ 1.7 for the data taken from [10].…”