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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Cr2GaC by Materials Project

Cr2GaC is H-Phase structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Cr is bonded in a 3-coordinate geometry to three equivalent Ga and three equivalent C atoms. All Cr–Ga bond lengths are 2.65 Å. All Cr–C bond lengths are 1.97 Å. Ga is bonded to six equivalent Cr and six equivalent Ga atoms to form distorted GaCr6Ga6 cuboctahedra that share corners with six equivalent GaCr6Ga6 cuboctahedra, corners with six equivalent CCr6 octahedra, edges with six equivalent GaCr6Ga6 cuboctahedra, edges with six equivalent CCr6 octahedra, and faces with six equivalent GaCr6Ga6 cuboctahedra. The corner-sharing octahedral tilt angles are 19°. All Ga–Ga bond lengths are 2.87 Å. C is bonded to six equivalent Cr atoms to form CCr6 octahedra that share corners with six equivalent GaCr6Ga6 cuboctahedra, edges with six equivalent GaCr6Ga6 cuboctahedra, and edges with six equivalent CCr6 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

The synthesis and electrical transport properties of carbon/Cr 2 GaC MAX phase composite microwires

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 Cr2GaC wires, and advanced low temperature electronic transport measurements revealed resistivity behavior dominated by amorphous carbon. Here, 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.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗