Amagai Y, Shimazaki T, Okawa K, Kawae T, Fujiki H, Kaneko N-H
National Institute of Advanced Industrial Science and Technology (AIST), National Metrology Institute of Japan (NMIJ), Tsukuba 305-8563, Japan.
Department of Applied Quantum Physics, Kyusyu University, Fukuoka 819-0395, Japan.
Rev Sci Instrum. 2020 Jan 1;91(1):014903. doi: 10.1063/1.5122226.
The intrinsic properties of superconductors enable the direct determination of the absolute Seebeck coefficient at low temperature due to the disappearance of the Seebeck effect to obey the Meissner effect. We report a precision absolute Seebeck coefficient measurement for the fine Pt sample determined using the high-Tc YBaCuO (YBCO) superconductor as a reference and an analysis of the measurement uncertainty. To make a precision measurement and aid in the verification of the uncertainty components, we developed a cryostat system that enables temperature control in a stable manner. The expected performance of the reference superconductor yielded a zero value well below Tc, which was validated by a superconductor-superconductor thermocouple experiment. Uncertainty analysis shows that the main limiting factor for this measurement is the accuracy of the temperature difference measurement using the resistance temperature sensors, along with its analog noise. We obtained values of S = 5.6 ± 0.2 µV/K with a relative expanded uncertainty of 3% at 80 K and precisely compared the Pt value with that determined by the high-Tc BiSrCaCuO (Bi-2223) superconductor, which has a higher Tc. We found that there was no difference between the Seebeck coefficient values obtained from the YBCO and Bi-2223 references up to its Tc within the expanded measurement uncertainties of 0.3 µV/K (2σ). These results provide accurate validation that the high-Tc superconductor is a useful reference up to the liquid nitrogen temperature.
超导体的本征特性使得在低温下能够直接测定绝对塞贝克系数，这是因为塞贝克效应消失以遵循迈斯纳效应。我们报告了使用高温超导钇钡铜氧（YBCO）超导体作为参考对精细铂样品进行的精密绝对塞贝克系数测量以及测量不确定度分析。为了进行精密测量并有助于验证不确定度分量，我们开发了一种能够稳定控制温度的低温恒温器系统。参考超导体的预期性能在远低于临界温度（Tc）时产生零值，这通过超导体 - 超导体热电偶实验得到了验证。不确定度分析表明，该测量的主要限制因素是使用电阻温度传感器测量温差的精度及其模拟噪声。我们在80 K时获得了S = 5.6 ± 0.2 μV/K的值，相对扩展不确定度为3%，并将铂的值与由具有更高Tc的高温超导铋锶钙铜氧（Bi - 2223）超导体确定的值进行了精确比较。我们发现，在0.3 μV/K（2σ）的扩展测量不确定度范围内，从YBCO和Bi - 2223参考获得的塞贝克系数值在其Tc以下没有差异。这些结果提供了准确的验证，即高温超导体在液氮温度以下是一种有用的参考。
