Synthesis and Characterization of Na-doped Cu0.5Tl0.5Ba2Ca2Cu3-xNaxO10-δ (x=0, 1, 2,2.5, 3) and Cu0.5Tl0.5Ba2CaMgCu3-xNaxO10-δ (x=0, 1, 2, 3) samples

Abstract

To examine the role played by lighter alkali atoms in oxide superconductors of high critical temperature(Tc) superconductivity, the samples of the following compounds Cu0.5Tl0.5Ba2Ca2Cu3- xNaxO10-δ(x=0,1,2,2.5,3) and Cu0.5Tl0.5Ba2CaMgCu3-xNaxO10-δ (x=0, 1, 2, 3) have been prepared. These analyses would clarify the significance of interactions of electrons with phonons in the process of the high-critical-temperature(Tc) superconductivity as well as the involvement of extra electrons in the CuO2 planes. These samples show an orthorhombic crystal structure with decreased unit-cell volume due to higher Na-doping in the final product. In terms of resistivity measurements, the metallic variations in resistivity down to 77K and critical temperatures at zero resistivity are 94.91K, 94.7K, 91.63K and 95.2K, 93.6,K 92.8K values for the prepared Cu0.5Tl0.5Ba2Ca2Cu3- xNaxO10-δ (x= 0, 1, 2) and Cu0.5Tl0.5Ba2CaMgCu3-xNaxO10-δ (x= 0, 1, 2) samples respectively. Suppression of the velocity of fermi surface ‘VF’, the zero resistance coherence-length, (along c axis) ‘ξc(0)’, the interlayer coupling constant ‘J’, and the phase-relaxation time of the carriers ‘τϕ’ are demonstrating a loss in the superconducting carriers’ density in Na-doped, according to the Fluctuation-induced conductivity(FIC) analysis of Cu0.5Tl0.5Ba2Ca2Cu3-xNaxO10-δ (x=0, 1, 2) samples. However, compared to undoped ‘samples, the values for, BC0(T), BC1(T), and, (Jc(0)) is increased indicating an increase in the population of inadvertently localized defects that acts as the pining centers and hence also shows an increasing trend in the values for these mentioned superconducting-parameters. While the zero resistance coherence-length, (along c-axis) ‘ξc(0)’, the velocity of fermi surface ‘VF’ , the inter layer’ coupling constant ‘J’, and the phase-relaxation time of carriers ‘τϕ’ are marginally increased for, -Cu0.5Tl0.5Ba2CaMgCu3-xNaxO10-δ (x=0, 1, 2) samples, demonstrating a small increase in the carriers’ density in the above mentioned samples. The marginal suppression of BC0(T)), (BC1(T)), and (JC(0) values) in Cu0.5Tl0.5Ba2CaMgCu3-xNaxO10-δ (x= 0, 1, 2)-samples showing an increase in the population of inadvertently localized defects. By increasing the doping concentration, of Na to pure 1223 samples, the -phonon-modes of oxygen(O2) are going softened which is most likely caused by the suppressed oscillator strength in Na-doped materials. The doping concentration, of Na in the final(1223) ‘samples shows the reduction in the density of free carriers at the planar sites of CuO2/NaO2 in these samples, which in turn shows suppression in the real (ε ′ )part, imaginary-part(ε ′′) of the dielectric’s constant, & the -ac-conductivity( σac).