A novel route to phase formation of cobalt oxyhydrates using KMnO4 as an oxidizing agent

TL;DR

This paper presents a new method using KMnO4 to synthesize sodium cobalt oxyhydrate superconductors, avoiding traditional bromine-based solutions, and explores how KMnO4 ratio affects structure and superconductivity.

Contribution

The study introduces a novel KMnO4-based synthesis route for sodium cobalt oxyhydrate superconductors, providing an alternative to conventional methods and analyzing its effects on material properties.

Findings

Successful synthesis of superconductors using KMnO4 as oxidant.

Higher KMnO4 ratios lead to more Na+ removal and c-axis expansion.

Superconducting transition temperature ranges from 3.8 to 4.6 K.

Abstract

We have first succeefully synthesized the sodium cobalt oxyhydrate superconductors using KMnO4 as a de-intercalating and oxidizing agent. It is a novel route to form the superconductive phase of NaxCoO2.yH2O without resorting to the commonly used Br2/CH3CN solution. The role of the KMnO4 is to de-intercalate the Na+ from the parent compound Na0.7CoO2 and oxidize the Co ion as a result. The higher molar ratio of KMnO4 relative to the sodium content tends to remove more Na+ from the parent compound and results in a slight expansion of the c-axis in the unit cell. The superconducting transition temperature is 4.6-3.8 K for samples treated by the aqueous KMnO4 solution with the molar ratio of KMnO4 relative to the sodium content in the range of 0.3 and 2.29.