The research in MAX phases is mainly concentrated on the investigation of carbides rather than nitrides (currently >150 carbides and only <15 nitrides) that are predominantly synthesized by conventional solid-state techniques. This is not surprising since the preparation of nitrides and carbonitrides is more demanding due to the high stability and low diffusion rate of nitrogen-containing compounds. This leads to several drawbacks concerning potential variations in the chemical composition of the MAX phases as well as control of morphology, the two aspects that directly affect the resulting materials properties. Here, we report how alternative solid-state hybrid techniques solve these limitations by combining conventional techniques with nonconventional precursor synthesis methods, such as the “urea–glass” sol–gel or liquid ammonia method. We demonstrate the synthesis and morphology control within the V–Ga–C–N system by preparing the MAX phase carbide and nitridethe latter in the form of bulkier and more defined smaller particle structuresas well as a hitherto unknown carbonitride V2GaC1–x N x MAX phase. This shows the versatility of hybrid methods starting, for example, from wet chemically obtained precursors that already contain all of the ingredients needed for carbonitride formation. All products are characterized in detail by X-ray powder diffraction, electron microscopy, and electron and X-ray photoelectron spectroscopies to confirm their structure and morphology and to detect subtle differences between the different chemical compositions.

MAX phases that exhibit long-range magnetic order in the bulk are still very hard to synthesize. Chromium and manganese are the cutoff elements when transitioning through the 3dmetals that still form stable full and doped MAX phases, respectively. An iron-based (on the M-site) bulk MAX phase does not exist. Therefore, other strategies to induce long-range magnetic ordering in bulk MAX phases are necessary to open the path to new functional materials. Here, we demonstrate the nonconventional synthesis of a hitherto unknown MAX phase solid-solution (V1–x Cr x )2GaC by microwave heating. The full series with 0 < x < 1 (x = 0.20, 0.40, 0.50, 0.60, 0.80) forms almost single phase with minimal differences in their morphology. Their magnetic properties, however, differ rather significantly, with a maximum susceptibility around x = 0.80. Both the experimental and theoretical/ab initio magnetic analysis confirm that the solid-solution (V1–x Cr x )2GaC is an itinerant Pauli paramagnet that almost fulfills the Stoner criterion for ferromagnetic order (for compositions with x around 0.80). This is a powerful insight into how chemical composition couples with electronic structure and the resulting bulk magnetic properties because it provides crucial guidelines to produce long-range ordered magnetic MAX phases.

MAX phases are layered solids with unique properties combining characteristics of ceramics and metals. MXenes are their two‐dimensional siblings that can be synthesized as van der Waals stacked and multi‐/single‐layer nanosheets, which possess chemical and physical properties that make them interesting for a plethora of applications. Both families of materials are highly versatile in terms of their chemical composition and theoretical studies suggest that many more members are stable and can be synthesized. This is very intriguing because new combinations of elements, and potentially new structures, can lead to further (tunable) properties. In this review, we focus on the synthesis science (including non‐conventional approaches) and structure of members less investigated, namely compounds with more exotic M‐, A‐, and X‐elements, for example nitrides and (carbo)nitrides, and the related family of MAB phases.

In contrast to ternary oxides, the number of known ternary nitrides is an order of magnitude lower, which is partially the result of their less exothermic free energy of formation and the resulting lower thermodynamic stability. This challenges experimentalists to continuously explore the synthetic parameter space and push toward new nitride phases. Here, we demonstrate the synthesis of a hitherto unknown orthorhombic structure of Cr 3 GeN, which typically crystallizes in a tetragonal structure. As derived from density functional theory calculations, formation energies of both phases are similar, and orthorhombic Cr 3 GeN can be stabilized by choosing lower reaction temperatures. According to detailed thermodynamic analysis, the new compound is stable up to 500 °C and exhibits the same phase transitions as the tetragonal phase at higher temperatures. Magnetic characterization suggests antiferromagnetic order for both polymorphs.