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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 exoticM‐,A‐, andX‐elements, for example nitrides and (carbo)nitrides, and the related family of MAB phases.

 

While MAX phases offer an exotic combination of ceramic and metallic properties, rendering them a unique class of materials, their applications remain virtually hypothetical. To overcome this shortcoming, a sol–gel based route is introduced that allows access to microwires in the range of tens of micrometers. Thorough structural characterization through XRD, SEM, EDS, and AFM demonstrates a successful synthesis of carbonaceous Cr 2 GaC wires, and advanced low temperature electronic transport measurements revealed resistivity behavior dominated by amorphous carbon. The tunability of electronic behavior of the obtained microwires is shown by a halide post-synthesis treatment, allowing purposeful engineering of the microwires’ electrical conductivity. Raman studies revealed the polyanionic nature of the intercalated halides and a slow decrease in halide concentration was concluded from time-dependent conductivity measurements. Based on these findings, the process is considered a viable candidate for fabricating chemiresistive halogen gas sensors. 

Microwave heating methods offer unique advantages in preparations of inorganic solids due to the high heating rates, potentially selective heating, and time/energy reductions. Understanding of these enhancements as well as involved mechanisms is poor due to the lack of available and easily applicable in situ monitoring methods, particularly for samples in the solid state. Existing in situ studies typically rely on access to beamline facilities as well as custom‐built microwave systems, which is in the best case inconvenient and in the worst case not achievable. In situ Raman spectroscopy is an ideal technique as it provides rapid and unambiguous phase identification by a noncontact method. Further, the instrument components are simple and compact, facilitating use in the typical synthetic laboratory. Only a few reports on using Raman spectroscopy for in situ measurements during microwave heating exist, and they all utilize specialized custom reactor setups. In this work, a new Raman measurement system designed to observe inorganic transformations in situ that is readily deployable in a standard, commercially available laboratory scale microwave reactor is described. As a simple demonstration, the anatase‐to‐rutile phase transition in TiO₂is monitored under both microwave and conventional furnace heating. The excellent time resolution achieved demonstrates the utility of the system in understanding microwave‐assisted methods for the preparation of inorganic compounds. The simplicity will encourage integration by the non‐specialist to understand microwave heating for synthetic preparations and promote wider application of the technique.