Thermoelectrics based on strontium titanate

Thermoelectric energy conversion technology is attracting great attention for the conversion of waste heat into electricity. For practical thermoelectric applications, the figure of merit for thermoelectric performance ZT needs to be >1. Although heavy-metal-based materials such as Bi2Te3 and PbTe exhibit ZT ∼ 1, they are not attractive for applications because they are mostly toxic and decomposition, vaporization, or melting of the constituents can easily occur at high temperatures. We review a new class of thermoelectric material based on a metal oxide: a two-dimensional electron gas (2DEG) in SrTiO3. The 2DEG demonstrates a Seebeck coefficient S that is enhanced by a factor of ∼5 compared with the bulk and an optimized ZT that reaches 2.4, twice that of conventional thermoelectric materials.