Synthesis and Stoichiometry of MgB2

TL;DR

This study investigates the synthesis, stoichiometry, and structural properties of MgB2, revealing it as a nearly stoichiometric compound with minor Mg vacancies and examining how composition affects lattice parameters and superconducting temperature.

Contribution

It provides detailed analysis of MgB2's nonstoichiometry, lattice changes, and superconducting properties, highlighting the effects of synthesis conditions and impurities.

Findings

MgB2 is a line compound with about 1% Mg vacancies.

Small lattice constant changes are due to grain interaction stresses.

Superconducting Tc decreases slightly with Mg-rich impurity doping.

Abstract

The system MgxB2 has been investigated to investigate possible nonstoichiometry in MgB2. When synthesized at 850oC, MgB2 is a line compound with a possible Mg vacancy content of about 1%. Small changes in lattice constants as a function of starting composition result from grain interaction stresses, whose character is different in the Mg-rich, near-stoichiometric, and Mg-deficient regimes. A small linear decrease of the superconducting transition temperature, Tc, in the Mg-rich regime results from accidental impurity doping.