Optimization of synthetic parameters for Tl-2201 superconducting phase by flash sintering process

Abstract

Samples with nominal composition Tl 2Ba 2Cu 1.2 (copper-rich Tl-2201) were calcined at various temperature, i.e. from 865 °C to 910°C and for various durations (10–20 h). The samples were sintered for 3 1 2 min at various temperatures. The X-ray powder diffraction pattern indicates that most of the Tl-Ba-Cu samples (Tl-2201) are single-phase materials. All the lines in the X-ray pattern are indexable on a tetragonal unit cell showing tetragonal symmetry having space group 14/mmm with a=3.86 A ̊ c=23.11 ± 0.06 A ̊ as unit cell parameters. R−T and AC susceptibility measurements show T on c, from 90 to 104 K. There is an elongation of the c-axis ( c=23.24 A ̊ ) for the sample showing the highest T c. Wet chemical analysis confirms the deficiency of thallium. This suggests some substitution of Cu in place of thallium which leads to an increase in the average oxidation state of copper, responsible for the creation of holes (charge carriers).