Effects of Nb substitution at Cu site on superconductivity and structural properties of TI₀.₉Cr₀.₁Sr₂Ca₀.₉₅Ge₀.₀₅Cu₂₋ᵪNbᵪ*0₇-δ (x = 0 - 0.2) superconductors / Muliana Ismail

The effects of Cu substitution by Nb on superconductivity and structural properties of Tlo.9Cro.iSr2Ca0.95Geo.o5Cu2-JNbJ07^ (x= 0 - 0.2) were investigated. The sample was prepared by using conventional solid-state synthesis method with different concentration of Niobium (Nb = 0, 0.05, 0.1, 0.15, 0.2). X-ray diffraction (XRD) measurement showed formation of dominant 1212 phase and minor 1201 phase. The substitution also caused the c-lattice parameter to decrease from 12.118 A to 12.095 A with Nb content. Electrical resistivity measurements showed all samples exhibit metallic normal state behavior with zero resistivity critical temperature, Tc:ero increasing from 88.6 K (x=0) to 89.6 K (x-0.05) before decreasing to 88.1 K (x=0.2). The best superconducting behavior was observed at x=0.05 with Tc -ero of 89.6 K and Tc onse, of 101.6 K respectively. The average grain size of the samples were almost constant around 4-6 urn. The effect of Nb substitution is discussed in term of decreasing c-lattice parameter, average Copper valence and formation of CuC>2 mixed plane which enhanced the superconducting temperature.