Is La3Ni2O6.5 a Bulk Superconducting Nickelate?

TL;DR

This paper investigates the reduction process of La3Ni2O7 to a metastable phase La3Ni2O6.45, providing insights into nickelate systems and their potential for superconductivity, though the phase itself does not superconduct at tested conditions.

Contribution

It reports the synthesis and characterization of a new metastable nickelate phase, La3Ni2O6.45, and discusses its implications for understanding nickelate superconductivity.

Findings

La3Ni2O6.45 is a metastable phase derived from La3Ni2O7.

The reduced phase does not exhibit superconductivity at ambient or high pressures.

Insights into the Ni-327 system and oxygen content effects on nickelates.

Abstract

Superconducting states onsetting at moderately high temperatures have been observed in epitaxially-stabilized RENiO2-based thin films. However, recently it has also been reported that superconductivity at high temperatures is observed in bulk La3Ni2O7-{\delta} at high pressure, opening further possibilities for study. Here we report the reduction profile of La3Ni2O7 in a stream of 5% H2/Ar gas and the isolation of the metastable intermediate phase La3Ni2O6.45, which is based on Ni2+. Although this reduced phase does not superconduct at ambient or high pressures, it offers insights into the Ni-327 system and encourages the future study of nickelates as a function of oxygen content.