New heat treatment to prepare high quality polycrystalline and single crystal MgB2 in single process

TL;DR

This paper introduces a novel heat treatment process that produces high-quality polycrystalline and single crystal MgB2 samples simultaneously, with detailed characterization confirming their excellent properties.

Contribution

The study presents a new single-step heat treatment method for synthesizing both dense polycrystalline and single crystal MgB2, enhancing efficiency and quality.

Findings

Polycrystalline MgB2 has RRR=16.6 and low resistivity at 40K.

Polycrystals show high density and well-coupled grain boundaries.

Single crystals exhibit weak flux pinning, indicating high purity.

Abstract

We report here on a new heat treatment to prepare both dense polycrystalline and single crystal MgB2 high quality samples in one single process. Resistivity measurements for polycrystalline part of the sample gives a residual resistivity ratio RRR=16.6 and a very low normal state resistivity rho(40K)= 0.28 microOhmcm. Both SEM and SQUID study on polycrystals reveal the high quality, dense character and well coupling of grain boundaries. On the other hand, the high quality single crystals have a unique shape that resembles the hexagonal crystal structure. SQUID measurements reveals very weak flux pinning character implying our single crystals to be very clean. In this study, we conclude that heat treatment is playing a major rule on the characteristics of both polycrystalline and single crystal MgB2. Samples are thoroughly characterized by x-ray, resistivity, dc SQUID and SEM.