Single crystal growth of MgB2 and thermodynamics of Mg-B-N system at high pressure

TL;DR

This paper reports the high-pressure growth of MgB2 single crystals via MgNB9 decomposition, analyzing their properties and the thermodynamics of the Mg-B-N system, revealing stability and doping effects.

Contribution

It introduces a method for growing MgB2 single crystals at high pressure and investigates their thermodynamic stability and doping effects.

Findings

MgB2 crystals up to 1.5x0.9x0.2 mm3 size

Transition temperature between 37 and 39 K

MgB2 stable up to 2190°C at high pressure

Abstract

Single crystals of MgB2 have been grown at high pressure via the peritectic decomposition of MgNB9. The crystals are of a size up to 1.5x0.9x0.2 mm3 with a weight up to 0.23 mg, and typically have transition temperatures between 37 and 39 with a width of 0.3-0.5 K. Investigations of the P-T phase diagram prove that the MgB2 phase is stable at least up to 2190 C at high hydrostatic pressure in the presence of Mg vapor under high pressure. Small variations of Tc are caused by doping with metal elements from the precursor or annealing of defects during the crystal growth process.