Lanthanum erbium carbide, La0.5Er0.5C2, a salt-like carbide with a cubic fluorite phase structure, was produced from 13C, allowing carbon diffusion rate to be determined using 12C. The carbon diffusion rate in La0.5Er0.5C2 was determined to be 2.0 x 10−13cm2/s at 850C, increasing to 1.8 x 10−11 cm2/s at 1150C, with an activation energy of about 95kJ/mol. These diffusion rates were too low for a carbon-ion fuel cell, but a number of other salt-like carbides exist. Be2C, in particular, was a salt-like carbide with an antifluorite structure, and should have higher carbon-ion diffusion than cubic La0.5Er0.5C2 due to the unoccupied octahedral sites in the antifluorite structure, but Be2C presents special difficulties due to the toxic nature of its hydrolysis products.

Carbon Diffusion in Lanthanum Erbium Carbide Stabilized in the Cubic Fluorite Structure. W.N.Simmons, F.H.Cocks: Journal of Phase Equilibria and Diffusion, 2012, 33[2], 85-8