Top-Seeded Melt-Growth of YBa_2Cu_3O_x Crystals for Neutron Diffraction Studies

TL;DR

This paper reports the successful growth of large, high-quality YBa2Cu3Ox crystals suitable for neutron diffraction, with optimized conditions and detailed structural characterization, advancing materials for superconductivity research.

Contribution

It introduces a top-seeded melt-growth method for producing large YBa2Cu3Ox crystals with high phase purity and detailed neutron diffraction analysis of their structure.

Findings

Crystals of cubic centimetre size were grown successfully.

The addition of Y2BaCuO5 and Pt improved crystal quality.

Neutron diffraction revealed high oxygen order and domain structure.

Abstract

We have grown cubic centimetre-size crystals of YBa2Cu3Ox suitable for neutron studies, by a top-seeded melt-growth technique. Growth conditions were optimized with an eye toward maximizing phase purity. It was found that the addition of 2% Y2BaCuO5 and 0.5% Pt (by mass) were required to prevent melt loss and to obtain the highest crystallinity. A neutron diffraction study on a mosaic of six such crystals found that the final Y2BaCuO5 concentration was 5%, while other impurity phases comprised less than 1% by volume. The oxygen content was set to x=6.5, the crystals were detwinned and then carefully annealed to give the well-ordered ortho-II phase. The neutron study determined that 70% of the mosaic's volume was in the majority orthorhomic domain. The neutron (0,0,6) and (1,1,0) rocking curve widths were ~1 degree per crystal and \~2.2 degrees for the mosaic, and the oxygen chain correlation lengths were >100 A in the a- and b-directions and ~50 A in the c-direction.