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Examination of superconducting ceramics by modified inductance probe methods

Journal of Magnetism and Magnetic Materials
Publication Date
DOI: 10.1016/0304-8853(91)90120-y
  • Physics


Abstract The inductance probe technique for determining superconducting properties has been extended to include monitoring the Q-factor ( Q) of the coil, with and without a superconductor present, as a function of temperature ( T). The Q vs. T plots display a sharp minimum near the superconducting transition temperature T c as a result of the combination of changes in inductance caused by the Meissner effect and the temperature variation of the dielectric loss ϵ″ of the superconductor. This provides a precision method of determining T c and the width of the superconducting transition and also enables the dielectric loss to be examined both near and above T c. The new method has been applied to examination of some Y-Ba-Cu-O and Tl-Ca-Ba-Cu-O sintered pellets. The critical temperatures are found to be 92 and 120 K respectively in good agreement with previous estimates. From the Q vs. T variation for Y-Ba-Cu-O the dielectric loss at 140 K is found to be ϵ″ = 0.065 and the temperature variation of loss, which is linear over the range 105 to 220 K, is ∂ϵ″/∂ T = 0.76×10 -4K 1. These values are in good order of magnitude agreement with Trybula et al.'s dielectric measurements using microwave electric fields and a Y-Ba-Cu-O specimen of nominally similar composition.

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