Synthesis, characterization and first principle modelling of the MAB phase solid solutions: (Mn1-xCrx)2AlB2 and (Mn1-xCrx)3AlB4

Luke A Hanner,Hussein O Badr,Martin Dahlqvist,Sankalp Kota,David Raczkowski,Johanna Rosen,Michel W Barsoum

doi:10.1080/21663831.2020.1845834

Luke A Hanner, Hussein O Badr + Show 5 more

Open Access

https://doi.org/10.1080/21663831.2020.1845834

Copy DOI

Abstract

ABSTRACT The MAB phases are a family of layered ternary transition metal borides, with atomically laminated crystal structures comprised of transition metal boride (M-B) layers interleaved by single, or double, Al (A) layers. Herein, density functional theory is implemented to evaluate the thermodynamic stability of disordered (Mn1-xCrx)2AlB2, and disordered and ordered (Mn1-xCrx)3AlB4 quaternaries. The (Mn1-xCrx)2AlB2 solid solutions were synthesized over the entire range of substitution. A (Mn1-xCrx)3AlB4 solid solution was produced, on the base of Cr3AlB4, to form (Mn0.33Cr0.66)3AlB4. Powder X-ray diffraction shows lattice parameter shifts and unit cell expansions indicative of successful solid solution formations.

Highlights

The MAB phases are a family of atomically laminated, ternary, transition metal borides, wherein M is a transition metal, A is generally aluminium, Al, and B is boron
To date the only 314 MAB phase synthesized is Cr3AlB4 that crystallizes in the Pmmm space group
Both Mn2AlB2 and Cr2AlB2 are stable with calculated formation enthalpies of −67 and −30 meV/atom, respectively

Summary

Introduction

The MAB phases are a family of atomically laminated, ternary, transition metal borides, wherein M is a transition metal, A is generally aluminium, Al, and B is boron. The first MAB phase, MoAlB, was synthesized in 1966 by Jeitschko et al [1], followed by Mn2AlB2 [2] and Fe2AlB2 [3] later that same year. A more complete history and summary of the MAB phases and their properties can be found in Ref. The MAB phase structure contains either single, or double, Al atomic layers sandwiched between two MB layers (Figure 1(a–b)) [10]. All structures examined contain a single Al atomic layer. The 212 MABs, Mn2AlB2 and Cr2AlB2, are isostructural and crystallize in the Cmmm space group [11]. To date the only 314 MAB phase synthesized is Cr3AlB4 that crystallizes in the Pmmm space group. In the 212 MAB structures, the layers stack in the b-direction; in the 314 they stack in the c-direction

Objectives

Methods

Results

Conclusion