Strategies for engineering phonon transport in Heusler thermoelectric compounds

Thermoelectric generators, which can convert waste heat directly into electricity, are promising candidates for capturing low-grade heat and enhancing the efficiency of the heat engines. This would lead to decreasing the fossil fuel usage and greenhouse gas emission. Many Heusler compounds have been studied for thermoelectric application due to their desired characteristics such as sizeable thermoelectric power factor, non-toxicity, and high stability over a wide temperature range. The primary restriction for Heusler thermoelectric materials has been their high lattice thermal conductivity, which reduces their thermoelectric figure of merit. Several strategies have been carried out to ameliorate this restriction by engineering the phonon transport properties. This article discusses several approaches such as bulk nanostructuring, the creation of point defects and vacancies, impurity doping, and multiphase engineering of the material structure for reducing the thermal conductivity of the Heusler compounds. The effectiveness of each of these methods depends on temperature; hence, the working temperature must be taken into account when designing the material structure and the composition to achieve the optimum performance for practical applications.