Thermoelectric Oxides and Oxynitrides with Perovskite-type Structure
- PDF / 925,675 Bytes
- 7 Pages / 595 x 842 pts (A4) Page_size
- 95 Downloads / 210 Views
1044-U07-09
Thermoelectric Oxides and Oxynitrides with Perovskite-type Structure Anke Weidenkaff1, Laura Bocher2, Rosa Robert2, Myriam Aguirre2, and Dmitry Logvinovich2 1 Solid State Chemistry and Catalysis, Empa, Ueberlandstr. 129, Duebendorf, 8600, Switzerland 2 Empa, Duebendorf, 8600, Switzerland
Abstract Transition metal oxides with perovskite-type structures are potential high temperature stable thermoelectric materials. The itinerant charge carrier concentration can be tuned for a targeted thermoelectric performance by controlled variation the composition and crystal structure. With innovative soft chemistry synthesis procedures the crystallite size in complex oxide ceramics with perovskite-type structure can be decreased compared to classical synthesis routes and allows to lower the heat conductivity dramatically while a large power factor can be maintained at the same time. Submicron crystallites with an enhanced number of twinned domains are beneficial to lower the lattice thermal conductivity without influencing the electron mobility. In this work, perovskite-type cobaltates, titanates, molybdates and manganates are studied for application as n- and p-type legs of thermoelectric oxide modules. The influence of heterostructures and nanocrystalline domains in perovskite oxides/oxynitrides and the correlation with transport properties and Seebeck coefficient will be discussed.
Introduction The use of geothermal or solar heat as energy source for thermoelectric generators is an attractive and environmentally clean way to generate electrical power [1, 2]. The advantage of thermoelectric converters is that they do not depend on mechanical or chemical conversion processes. Thus, they can be applied in a decentralised location where geothermal and solar heat is abundant i.e. under the earth surface, in the Sahara region, respectively. They are emission free during operation, noiseless and durable. The amount of electrical power produced is depending on the thermoelectric conversion efficiency of the device and the heat flux. The direct conversion of heat flux into electricity is connected to electron transport phenomena, and the interrelated Seebeck effect. The direct efficient thermoelectric conversion of solar or geothermal heat into electricity requires the development of p- and n-type semiconductors with similar materials properties. In general compounds exhibiting a large Seebeck coefficient S, high electrical conductivity σ, and a small thermal conductivity κ , in summary a large thermoelectric figure of merit Z are required (eq.1). Z = S2 σ/κ
eq.1
Since these transport properties are interconnected by the Wiedemann-Franz-Law for most materials, the development of a material breaking this relationship is a scientific challenge. Many conventional thermoelectric materials suffer from high toxicity, low stability in air and too low efficiency [3], while oxide ceramics are inert and extremely stable at high temperature in air. Nevertheless, ceramics are much less studied, since they have been only recently
Data Loading...
