Structure and thermal expansion of (Crx,V1−x)n+1AlCn phases measured by X-ray diffraction

• Published in: Journal of the European Ceramic Society Vol. 37; no. 1; pp. 15 - 21
• Main Authors: Halim, Joseph, Chartier, Patrick, Basyuk, Tatyana, Prikhna, Tatyana, Caspi, El’ad N., Barsoum, Michel W., Cabioc’h, Thierry
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2017; Elsevier
• Subjects: Carbides; MAX phases; Physics; Solid solutions; Thermal expansion; XRD; MAX phases; Thermal expansion; XRD; Solid solutions; Carbides; MAX Phases
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2016.07.022

MAX phases in the (Crx,V1−x)n+1AlCn system were synthesized by reactive sintering or hot isostatic pressing of elemental powders at temperatures between 1400°C and 1600°C. For n=1, a complete range (0≤x≤1) of solid solutions was found; for n=2 and 3 the solubility ranges were 0.25≤x≤0.75 and 0≤x≤0.5, respectively. Powder X-ray diffraction revealed that the lattice parameters of all (Crx,V1−x)n+1AlCn solid solutions followed Vegard’s law. The thermal expansion coefficients of the various compounds were determined from Rietveld refinements of X-Ray patterns obtained at temperatures between ambient and 800°C. For the n=1 and 3 phases the thermal expansion coefficients were almost isotropic; those for the n=2, however, were quite anisotropic with the expansion along the a-axis being significantly larger than along the c-axis. As a general trend, vanadium rich compounds have smaller thermal expansion coefficients than their Cr-rich counterparts.