Mechanical Properties of p- and n-Type Bismuth Telluride-Based Solid Solutions Doped with Graphene

The influence of the addition of nanodispersed graphene in an amount of 0.05-0.15 wt % on the ultimate compressive strength of the materials based on p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.4Se0.6 solid solutions is studied. The samples are fabricated by spark plasma sintering of the powders prepared by melt spinning and grinding in a ball mill. All samples are found to undergo brittle fracture. The microstructure of the cleavage of the p-type samples doped with graphene is lamellar, and the grains have pronounced facets. In the n-type materials, the grains have lost their facets and the graphene content increases. The p-type samples doped and undoped with graphene have the same ultimate strength, sigma(u )= 208 +/- 10 MPa. The ultimate strength of the n-type samples doped with graphene is sigma(u )= 222 +/- 10 MPa, and that of the plain sample is sigma(u) = 167 MPa.