pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2018; 68: 945-949

Published online September 28, 2018 https://doi.org/10.3938/NPSM.68.945

## Effects of Oxyanion Substitution on the Phase Formation and the Superconducting Properties of TlSr$_4$Cu$_2$O$_z$SO$_4$

Ho Keun LEE*

Department of Physics, Kangwon National University, Chuncheon 24341, Korea

Correspondence to:hklee221@kangwon.ac.kr

Received: August 7, 2018; Revised: August 16, 2018; Accepted: August 16, 2018

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

### Abstract

Polycrystalline samples of TlSr$_4$Cu$_2$O$_z$(SO$_4$)$_{1-x}$(BO$_3$)$_x$ and TlSr$_4$Cu$_2$O$_z$(SO$_4$)$_{1-y}$(CO$_3$)$_y$ with $0 \leq x \leq 0.3$ and $0 \leq y \leq 0.4$ were synthesized by using a solid state-state reaction method. The phase formation and the superconducting properties were investigated by means of X-ray diffraction and resistivity measurements. X-ray diffraction data revealed that the solubility limits of (BO$_3$) and (CO$_3$) were about $x$ = 0.1 and $y$ = 0.2, respectively. Resistivity measurements indicated that the transition temperature of TlSr$_4$Cu$_2$O$_z$(SO$_4$) did not change significantly with the substitution of either borate or carbonate oxyanions within the solubility limit. This result suggests that the solubility limit of oxyanion for sulfate depends on the oxyanion species.

Keywords: Oxyanion superconductor, Oxyanion substitution, Oxysulphate, TlSr$_4$Cu$_2$O$_z$SO$_4$