Unusual n-type thermoelectric properties of Bi2Te3 doped with divalent alkali earth metals

Publication date: Available online 13 October 2018Source: Journal of Solid State ChemistryAuthor(s): Sejin Byun, Joonil Cha, Chongjian Zhou, Yong Kyu Lee, Hyungseok Lee, Sang Hyun Park, Won Bo Lee, In ChungAbstractBi2Te3-based materials are a representative thermoelectric system operating near ambient temperature. Their n-type family is very limited and underperforms the p-type counterpart, which is a major concern in the thermoelectric community. Here we report that alkali earth metals (AE = Mg, Ca, Sr, Ba) in Group 2 unusually induce n-type thermoelectric properties in Bi2Te3. Mg is the most efficient electron donor among them. The x = 0.01 sample of MgxBi2-xTe3 (x = 0.005, 0.01, 0.015) system exhibits remarkably enhanced power factor and ZT of ~0.8 at 350 K in comparison with pristine Bi2Te3. The improved performance is attributed to simultaneously enhanced electrical conductivity and reduced lattice thermal conductivity. Remarkably, MgxBi2-xTe3 materials show larger Seebeck coefficients than those expected by the theoretical Pisarenko relation.Graphical abstract1% Mg doping increases charge carrier concentration and electrical conductivity. As a result, remarkably high power factor near ambient temperature is obtained in n-type Mg0.01Bi1.99Te3. Coupled with reduced lattice thermal conductivity, a high ZT of ~0.8 at 350 K is achieved for n-type Mg0.01Bi1.99Te3.

Source: Journal of Solid State Chemistry - October 14, 2018 Category: Chemistry Source Type: research