Thermal expansion measurements have been carried out on Fe substituted superconducting compounds Y1Ba2(Cu1−xFex)3Oy (0<x<4%) using a high resolution dilatometer employing the three terminal capacitance technique. The experimental set up is sensitive enough to detect changes in α of less than 10−8K−1. Results show that the jump Δα in the coefficient of linear thermal expansion at the superconducting transition temperature,Tc, increases almost linearly with Fe concentration. The normal state thermal expansion coefficient α first decreases, attains a minimum value aroundx=1% and then increases for higher Fe concentrations. The oxygen content per unit formula is almost constant up tox=1% and then increases rapidly withx. It has also been observed that the anomalous behaviour of α around 260 K observed by Meingastet al  for Fe concentrationx=5% is due to inadequate annealing of the sample.
Volume 97, 2023
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