pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2020; 70: 909-913

Published online November 30, 2020 https://doi.org/10.3938/NPSM.70.909

## Effects of Partial Substitution of Nitrate on 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 29, 2020; Revised: September 24, 2020; Accepted: September 24, 2020

### Abstract

The effects of partial substitution of nitrate groups at the SO$_{4}$ sites on the superconducting properties of the TlSr$_{4}$Cu$_{2}$O$_{z}$(SO$_{4}$)$_{1-x}$(NO$_{3}$)$_{x}$ system have been investigated. X-ray diffraction data showed that the solubility limit of (NO$_{3}$) was about $x$ = 0.35. The change in the solubility limit of oxyanion for sulfate was discussed in connection with the characteristics of the oxyanion species. Within the solubility limit, the introduction of the nitrate groups did not change significantly the transition temperature of the pristine TlSr$_{4}$Cu$_{2}$O$_{z}$(SO$_{4}$) compound. However, we found that compared to the pristine compound, the introduction of the nitrate groups degraded the stability properties of the sample after annealing at 400$^{\circ}$C in Ar atmosphere.

Keywords: Oxyanion superconductors, Nitrate substitution, Stability, TlSr$_{4}$Cu$_{2}$O$_{z}$ (SO$_{4}$)$_{1-x}$(NO$_{3}$)$_{x}$

### Figures

Fig. 1. Temperature dependences of the electrical resistivity for TlSr$_{4}$Cu$_{2}$O$_{z}$(SO$_{4}$)$_{1-x}$(NO$_{3}$)$_{x}$ samples.