Influences of Pb Substitution on Microstructure, Electrical Transport, and Mechanical Properties of Single-Crystal FeTe0.5Se0.5 Superconductors

In this work, single crystals of superconducting Fe1-xPbxTe0.5Se0.5 (x = 0.0, 0.01, 0.05, and 0.1) were grown by self-flux method. The structural, electrical, and mechanical properties of prepared samples were investigated. Structurally, it was determined that as the Pb ratio increased, the a- parameter of the crystal structure increased and the c-parameter decreased. SEM analysis showed that there was no significant microstructural change in Pb substituted FeSeTe material compared with the unsubstituted sample. There was a growth in the form of single-crystal sheets with thicknesses between 700 nm and 2 mu m. It was observed that the Pb substitution was not shown any positive change in the electrical properties compared to the unsubstituted FeSeTe system, and superconductivity deteriorated as the Pb concentration was increased. Similar trends were obtained both for the upper critical field, H-c2(T), and a characteristic length, xi(c). Relation between the mechanical properties and substitution ratio was also investigated. The hardness profiles value was found in the range of 0.90-0.49 GPa, while the elastic modulus was obtained between 19.4 and 7.84 GPa depending on the Pb substitution. It was seen that these values were slightly lower than the results obtained for unsubstituted FeSeTe material. This shows that Pb substitution has an effect on the elasticity of FeSeTe material.