Transition Metal (M = Rh and Ta) Effects on the Electrical Properties and AC Susceptibility of Tl0.85Cr0.15Sr2-xMxCaCu2O7 Superconductor

The effects of transition metal (M = Rh and Ta) on Tl0.85Cr0.15Sr2-xMxCaCu2O7 (Tl-1212) superconductor for x = 0 – 0.04 (M = Rh) and x = 0 – 0.30 (M = Ta) were studied. X-ray diffraction patterns showed Tl-1212, Tl-1201 and Ca0.3Sr07CuO2 phases in the samples. Scanning electron micrographs (SEM) showed that the grain size decreased with Rh. The transition temperature increased when Rh and Ta were substituted for low levels. AC susceptibility measurements showed the highest transition temperature Tcχ′ = 98 K for Rh (x = 0.02) and 96 K for Ta (x = 0.3) samples. The peak temperature, Tp of the imaginary susceptibility χ″ was the highest for Rh with x = 0.02 (Tp = 93 K) and Ta with x = 0.30 (Tp = 91 K). Rh and Ta improved the onset transition temperature of Tl0.85Cr0.15Sr2-xMxCaCu2O7 from 97 K to 103 K and 104 K, respectively.