Synthesis and Bulk Properties of Oxychloride Superconductor Ca2-xNaxCuO2Cl2

TL;DR

This study synthesizes Na-doped Ca2CuO2Cl2 superconductors under high pressure, revealing how synthesis conditions affect Na content and showing chlorine's lesser role than oxygen in charge transfer, impacting superconducting properties.

Contribution

It provides new insights into the synthesis parameters and the role of chlorine in charge transfer for oxychloride cuprate superconductors.

Findings

Na content depends on pressure, temperature, and time during synthesis.

Chlorine is less effective than oxygen in supplying charge carriers.

Superconducting transition temperature Tc is reduced with chlorine presence.

Abstract

Polycrystalline samples and submillimeter size single crystals of Na-doped Ca2CuO2Cl2 have been synthesized under high pressure. A series of experiments showed that the Na content depends not only on the pressure during the synthesis but also on the synthesis temperature and time. From a comparison of the Na-CCOC data with those of structurally related La214 cuprate superconductors we concluded that chlorine at the apical site is less effective that oxygen in supplying charge carriers to the CuO2 plans. As a result, the coupling between the CuO2 planes is weakened, the transition temperature Tc is reduced and the anisotropic nature is enhanced.