On the influence of rare-earth substitution for Ca in Bi(Pb):2212 superconducting system

We report here the mechanical and superconducting properties of pure and rare-earth elements R substituted Bi(Pb):2212 samples. Phase purity and microstructural examination are obtained by using XRD and SEM techniques. While the mechanical and superconducting properties are determined from microhardness, resistivity and Hall coefficient measurements. The XRD patterns of all samples indicated the presence of large amount of Bi:2212 phase along with minor amount of Bi:2201 phase. The SEM photographs show a clear change in the grain morphology for R substituted samples as compared to pure sample. On the other hand, the Vickers microhardness is gradually decreased with various R as one move towards the right in lanthanide series. The on-set temperatures Ton are found to be 87 K for pure sample and it decreased to 80, 68 and 36 K for Y, Gd and Nd samples, respectively. While La sample still remains non-superconductor. Although, the sign of Hall is positive for all samples, the carrier concentration is found to be decreased with various R. Our results are discussed in terms of the possible reasons for Tc depression by substitution of rare-earth elements at Ca site in Bi(Pb):2212 superconducting system.