Transcending the MAX phases concept of nanolaminated early transition metal carbides/nitrides -- the ZIA phases

TL;DR

This paper introduces ZIA phases, a new class of nanolaminated intermetallic compounds with complex structures, expanding the MAX phases concept to broader material properties and structural diversity.

Contribution

It proposes ZIA phases as a novel class of nanolaminated intermetallics, extending the MAX phases concept beyond early transition metal carbides/nitrides.

Findings

Nb3SiNi2 is a crystalline solid with a layered atomic structure.

ZIA phases follow a common stoichiometric rule with MAX phases.

The structural complexity of ZIA phases exceeds that of known MAX phases.

Abstract

A new potential class of nanolaminated and structurally complex materials, herein conceived as the Zigzag IntermetAllic (ZIA) phases, is proposed. A study of the constituent phases of a specific Nb--Si--Ni intermetallic alloy revealed that its ternary H-phase, \textit{i.e.}, the Nb$_3$SiNi$_2$ intermetallic compound (IMC), is a crystalline solid with the close-packed \textit{fcc} Bravais lattice, the 312 MAX phase stoichiometry and a layered atomic arrangement that may define an entire class of nanolaminated IMCs analogous to the nanolaminated ceramic compounds known today as the MAX phases. The electron microscopy investigation of the Nb$_{3}$SiNi$_{2}$ compound -- the first candidate ZIA phase -- revealed a remarkable structural complexity, as its ordered unit cell is made of 96 atoms. The ZIA phases extend the concept of nanolaminated crystalline solids well beyond the MAX phases family of early transition metal carbides/nitrides, most likely broadening the spectrum of achievable material properties into domains typically not covered by the MAX phases. Furthermore, this work uncovers that both families of nanolaminated crystalline solids, \textit{i.e.}, the herein introduced \textit{fcc} ZIA phases and all known variants of the \textit{hcp} MAX phases, obey the same overarching stoichiometric rule $P_{x+y}A_xN_y$, where $x$ and $y$ are integers ranging from 1 to 6.