Research Update: Oxide thermoelectrics: Beyond the conventional design rules

Abstract

Materials' design for high-performance thermoelectric oxides is discussed. Since chemical stability at high temperature in air is a considerable advantage in oxides, we evaluate thermoelectric power factor in the high temperature limit. We show that highly disordered materials can be good thermoelectric materials at high temperatures, and the effects of strong correlation can further enhance the figure of merit by adding thermopower arising from the spin and orbital degrees of freedom. We also discuss the Kelvin formula as a promising expression for strongly correlated materials and show that the calculation based on the Kelvin formula can be directly compared with the cross-layer thermopower of layered materials. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

Generalized Scharfetter–Gummel schemes for electro-thermal transport in degenerate semiconductors using the Kelvin formula for the Seebeck coefficient

“…N c (T ) g η (η n ) δΘ is the first-order exact solution of the BVP (41). Both schemes converge to the exact result as their first-order terms agree with J 1 .…”

“…T . The exact current J exact = J exact (δΦ, δη n , δΘ,η n ,T ) is a function of five parameters that satisfies the BVP (41). We solve the BVP (41) numerically using the shooting method [97], where we combine a 4th order Runge-Kutta method with Brent's root finding algorithm [98] .…”

“…In this paper, we will consider an alternative model for the Seebeck coefficient, which is the so-called Kelvin formula for the thermopower [32]. The Kelvin formula recently gained interest in theoretical condensed matter physics and has been shown to yield a good approximation of the Seebeck coefficient for many materials (including semiconductors, metals and high temperature superconductors) at reasonably high temperatures [32][33][34][35][36][37][38][39][40][41][42]. The Kelvin formula relates the Seebeck coefficient to the derivative of the entropy density with respect to the carrier density and therefore involves only equilibrium properties of the electron-hole plasma, where degeneration effects are easily included.…”

Novel Principles and Nanostructuring Methods for Enhanced Thermoelectrics

“…Liu et al give a detailed overview of the nanoapproach and the need to redefine ZT to be effective over the whole temperature range, i.e., ZT eng . There have also been recent good reviews dealing with particular classes of materials such as Zintl compounds, clathrates, half Heuslers, sulfides, borides, and oxides …”

Strongly correlated oxides for energy harvesting

“…It was also proposed theoretically that the 'pudding mold' type band structure contributes to the large Seebeck coefficient in NaCo 2 O 4 [3], and such a band structure was experimentally observed [4]. In addition to NaCo 2 O 4 , various cobalt oxides were investigated and found to exhibit large positive Seebeck coefficient, and thus can be good p-type thermoelectric materials [5][6][7]. On the other hand, the n-type version of this kind of materials has not been very much studied.…”