Nanoscratch and indentation fracture toughness in superconductor Ba–Fe–As single crystals with lamellar structure

Tribological aspects of Ba(Fe0.974Mn0.026)2As2 single crystals were analyzed through nanoscratch tests and correlated with fracture toughness data. The ~100µm thick samples present ab-planes stacked by following the c-axis (lamellar structure). Scratch hardness (0.31GPa for ab-plane and 2.10GPa for a(b)c-plane) and wear rate are in accordance with previous results for indentation hardness. Microcracking rules the scratching behavior of both planes, the ab-one presenting a marked critical load for cracking that is loading-rate dependent. Fracture toughness, estimated by the minimum load for crack nucleation in indentation tests, was statistically similar, 1.8±0.9MPam1/2 for the ab-plane and 1.5±0.5MPam1/2 for the a(b)c-plane. Results lead to the conclusion that the lamellar structure determines the material tribo-mechanical behavior. •Superconductor Ba(Fe0.974Mn0.026)2As2 single crystals, ~100µm thick, were produced.•Scratch deformation mechanism between ab- and a(b)c-planes is highly anisotropic.•Scratch hardness values were 2.10GPa [a(b)c-plane] and 0.31GPa (ab-plane).•Indentation fracture toughnesses were 1.5 [a(b)c-plane] and 1.8MPam1/2 (ab-plane).•The lamellar structure and the loading rate rule crack nucleation during scratching.