Significantly enhanced figure-of-merit in graphene nanoplate incorporated Cu2Se fabricated by spark plasma sintering

We have fabricated graphene nanoplate (GNP) incorporated Cu2Se using ball milling followed by a spark plasma sintering (SPS) process. All samples have been characterized comprehensively by high resolution transmission electron microscopy, room temperature and high temperature synchrotron X-ray diffraction, differential thermal analysis, and thermoelectric properties measurements. The GNP was found to be densely and homogeneously distributed inside the matrix material, leading to a large density of grain boundaries and refined Cu2Se grains as well as GNP/Cu2Se interfaces. Despite only slight changes to the electrical conductivity, Seebeck coefficient, and power factor as a result of the GNP incorporation, the figure-of-merit (zT) in GNP incorporated Cu2Se was enhanced by a factor of up to 1.7 at 873 K compared to the undoped sample. Our results indicate that it is the GNP/Cu2Se interfaces that play an important role in the great reduction of thermal conductivity and significantly enhancement of zT. This work provides a suitable strategy to apply carbon engineering to improve thermoelectric performance in the Cu2Se and other related compounds.