SIMULTANEOUS MEASUREMENT OF THERMAL CONDUCTIVITY AND THERMAL DIFFUSIVITY FOR SUPERCONDUCTING THIN FILMS (YBCO) BY PHOTOTHERMAL RADIOMETRY

摘要

In the development of superconducting tape of an Yttrium system superconductor (YBa2Cu3O7-δ: YBCO), thermal evaluation is one of the most important basic technology for the superconducting electric transmission system design. Specifically, it is necessary to consider the thermal behavior of the YBCO layer perpendicular to the surface. The purpose of the present study is to measure the thermal properties (thermal conductivity and thermal diffusivity) of the vertical direction of the YBCO thin films by the photothermal radiometry (PTR) under the normal temperature environment. PTR enables a contact-free and non-destructive measurement. First, we have performed sensitivity analysis on YBCO thermal properties by using the theory that expresses PTR and have examined measurement conditions. We have measured thermal properties of the YBCO thin films (1000 nm in thickness) and compared with those of the YBCO bulk. The results indicate that the thermal conductivity and thermal diffusivity of thin film are same level as the reported value of YBCO bulk. We have measured three samples with different thicknesses (1000 nm, 500 nm and 250 nm) and examined the film thickness dependency of thermal properties.