Superconductivity Measurements of (Hg,Tl)-1223 Compound Prepared in Capsule

B A Aljurani ,Ghazala Y Hermiz ,M F A Alias

doi:10.24996/ijs.2021.62.9.9

Abstract

In this paper, investigations were carried out on the effects of simultaneous partial substitution of Tl at the Hg site on the physical properties of an Hg1-xTlxBa2Ca2Cu3O8+δ cuprate superconductor with x= 0, 0.1, 0.2, 0.3 and 0.4. Two steps of the solid state reaction method were used to prepare samples in capsule. The results showed that the optimum sintering temperature was equal to 850 ᵒC and the sintering time was equal to 20 h for the prepared samples.  The best conditions for constitution and stabilization of the high Tc phase-1223 were obtained by investigating the effects of Tl substitution on Hg site and oxygen content (δ) on the superconducting properties. Structural investigation revealed that all the samples have a tetragonal structure with two phases, namely an Hg-1223 high Tc phase as a main phase and an Hg-1212 low Tc phase. Besides, some impurity phases like CuO and CaHgO2 were found. The increase of Tl content in Hg1-xTlxBa2Ca2Cu3O8+δ compound from 0 to 0.4 caused a change in the lattice parameter, density of the unit cell (ρm), and c/a values. HgBa2Ca2Cu3O8+δ compound exhibited a critical transition temperature that is equal to 115 K. On the other side, the results showed that the highest Tc was 119 K for Hg0.8Tl0.2 Ba2Ca2Cu3O8+δ. The oxygen content (δ= 0.46) was expected to be the optimum hole doping for Hg0.8Tl0.2 Ba2Ca2Cu3O8+δ compound, which means in our opinion that δ plays a remarkable role in the assessment of Tc.

Highlights

Mercury-based cuprates HgBa2Can-1CunO2n+2+δ, where n indicates the set of successive Cu-O layers, was first discovered in 1993 [1]
Types of superconductors as Hg-based high Tc are interesting for researchers because they have higher superconducting transition temperature (Tc =133 K for HgBa2Ca2Cu3O8+δ) [2]
The sample was annealed in an argon atmosphere and the Tc was increased to 132 K. They found that Tl substitution at the Hg site is an evidence of stabilization of the (Hg, Tl) – 1223 phase and the value of critical current density is approximately doubled in comparison to that value for the pristine Hg Ba2 (Ca1-xSrx)2Cu3O8+δ

Summary

Introduction

Mercury-based cuprates HgBa2Can-1CunO2n+2+δ, where n indicates the set of successive Cu-O layers, was first discovered in 1993 [1]. The sample was annealed in an argon atmosphere and the Tc was increased to 132 K They found that Tl substitution at the Hg site is an evidence of stabilization of the (Hg, Tl) – 1223 phase and the value of critical current density is approximately doubled in comparison to that value for the pristine Hg Ba2 (Ca1-xSrx)2Cu3O8+δ. Alias et al.[10] prepared superconductors at high temperature with Hg1-xTlxBa2Ca2Cu3O8+δ as a nominal composition for (0≤x≤0.4) via a two- steps solid state reaction in air. Their results showed that the optimum sintering temperature was 880 oC, whereas the sintering period was 100 h. This paper studies the effects of simultaneous partial substitution Tl at the Hg site on the physical properties, such as the structure, critical temperature and electrical resistivity, of Hg1xTlxBa2Ca2Cu3O8+δ compound with x= 0, 0.1, 0.2, 0.3 and 0.4, which is prepared in capsule

Experiments

Results and Discussion

Conclusions