Thermoelectric Materials and Devices - Hierarchical Nanostructures for Energy Devices - page 107

d n 3 r 4 n g | 7

CHAPTER 6
Thermoelectric Materials and
Devices

CHANYOUNG KANG, a HONGCHAO WANG, a
JE-HYEONG BAHK, b HOON KIM a AND WOOCHUL KIM* a

a School of Mechanical Engineering, Yonsei University, Seoul, Republic of
Korea; b Birck Nanotechnology Center, Purdue University, West Lafayette,
Indiana 47907, U.S.A.
*Email: [e-mail]

6.1 Introduction
Thermoelectric effects are the physical principles that are used to directly
convert heat into electricity or vice versa based on charge carrier and phonon
transport phenomena in a solid. 1-8 When a temperature gradient is imposed
on a solid, an electric potential is created due to the redistribution of charge
carriers in the material. This phenomenon is called the Seebeck effect. The
reverse phenomenon, in which a temperature difference is created across a
material by an electric current due to the lattice cooling or heating at the
interfaces, is called the Peltier effect. These two effects can be used in various
power generation and refrigeration applications via the thermal-to-electric
(or vice versa) energy conversion.
Thermoelectric effects were first discovered in the early 1820s and de-
veloped quickly through the 1850s. Their applications in thermoelectric
devices (power generation and refrigeration) were recognized during this
time period. 9 In the 1950s, there were many research activities on the use of
thermoelectric power generation for spacecraft. Prominent achievements
among these were the projects led by NASA to power spacecraft using

.