Effect of Nano-Sized Nickel Ferrite Addition on Superconducting Properties of (Tl<sub>0.85</sub>Cr<sub>0.15</sub>)Sr<sub>2</sub>CaCu<sub>2</sub>O<sub>7-δ</sub> Superconductors

Abstract

The effect of nanosized nickel ferrite (NiFe2O4) addition on (Tl0.85Cr0.15)Sr2CaCu2O7-δ superconductors has been investigated. (Tl0.85Cr0.15)Sr2CaCu2O7-δ high temperature superconductors was prepared via solid-state reaction method using high purity oxide powders. Nanosized NiFe2O4 was added to the compound at composition x = 0 - 0.003 wt.%. Samples were studied using scanning electron microscopy (SEM), X-ray diffraction method (XRD), electrical resistance versus temperature, transport critical current density Jc and AC susceptibility measurements. SEM micrographs showed close-packed microstructure with low porosity. XRD patterns showed a dominant phase of Tl-1212 with a minor phase of Tl-1201 for all samples. All of the samples displayed metallic normal state behavior before the onset transition temperature (Tc-onset) which was between 102 and 104 K. The transition temperature (Tcχ’) from AC susceptibility measurement also showed the similar results between 101 and 103 K. Tc-zero was slightly suppressed with the addition of nanosized NiFe2O4. The peak temperature Tp from the imaginary part of the susceptibility χ” was found between 77 - 91 K for all samples. The highest transport critical current density (Jc) at 77 K was shown by sample x = 0.001 wt.% at 2213 mAcm-2. Nanosized NiFe2O4 has significantly enhanced the Jc of (Tl0.85Cr0.15)Sr2CaCu2O7-δ superconductor.