Mg₂Si-based thermoelectric compounds with enhanced fracture toughness by introduction of dual nanoinclusions

Dual nanoinclusions of reduced graphene oxides (rGOs) and metal nanoparticles (NPs) were introduced into Al and Bi co-doped Mg₂Si thermoelectric (TE) compounds to enhance their fracture toughness (∼0.82 MPa m^1/2 for pristine Mg_1.96Al_0.04Si_0.97Bi_0.03). The TE performance of Mg_1.96Al_0.04Si_0.97Bi_0.03 decreased by the introduction of nanoscale inclusions, mainly owing to the deterioration of the electronic transport properties originated from increased electron scattering. However, a significantly enhanced fracture toughness of 2.26 MPa m^1/2 was achieved by the introduction of 3 vol% rGOs (∼5 nm thick and ∼3 μm wide) and 0.6 vol% Sn NPs (50–150 nm), owing to the simultaneous activation of three different inhibition mechanisms for crack propagation: bridging of cracks, sheet pullout within the crack, and deflection of crack propagation.