Date:
Thu, 29/12/2022 - 11:00 to 12:00
Location:
Los Angeles Bld., Jerusalem, Israel
Abstract
Thermoelectric (TE) technology can convert waste heat into useful electrical power, thereby
providing appropriate solutions for sustainable and clean energy demands. In this context, one of
the most significant challenges today is developing inexpensive materials with improved
conversion efficiency and chemical stability that sustain adequately high temperatures. What
hinders application of such TE devices in extensively commercial usage, such as vehicles, is
probably their limited commercial viability and thermal stability; this restricts their utilization to
relatively specific niches such as power generation for deep space missions.
The Technion Thermoelectric Materials Research Group focuses on two classes of bulk TE
materials, namely chalcogenide and metal-oxide based compounds; whereas the first one
provides solutions for highly-efficient energy conversion at the mid-range temperatures, the
second one is characterized by high chemical stability and inexpensive energy conversion at
elevated temperatures.
In this talk we will introduce strategies to develop TE materials with improved properties, which
are based on experimental procedures mostly, incl. materials synthesis, TE transport property
measurements, and high-resolution electron microscopy, and are supplemented by density
functional theory (DFT) calculations. We will show how controlled nucleation and growth of
second-phase precipitates in PbTe-based compounds result in scattering of heat-carrying
phonons, thereby reducing thermal conductivity and improving TE performance. Evaluation of
the growth and coarsening rates of Ag-rich precipitates in PbTe requires quantitative information
on the bulk diffusion of Ag in PbTe-matrix. To this end, we apply DFT calculations of the Ag-
diffusant’s vibrational frequencies and its activation energy for diffusion, which enables us to
derive the temperature-dependent diffusion coefficients. Furthermore, DFT calculations of point
defect energies, electronic density of states, and spatial charge distribution indicate that
interstitial diffusion is the governing mechanism, and is preferred compared to the vacancy
mechanism. We will also show how selective doping of CaO(CaMnO 3 ) m -based compounds at
preferred lattice sites enables us manipulating the energy barriers for charge carrier transport,
thereby enhancing their TE power factor.
These two selected case studies exemplify the use of computational tools to address fundamental
materials-science oriented issues that are involved in the design of TE materials.
Thermoelectric (TE) technology can convert waste heat into useful electrical power, thereby
providing appropriate solutions for sustainable and clean energy demands. In this context, one of
the most significant challenges today is developing inexpensive materials with improved
conversion efficiency and chemical stability that sustain adequately high temperatures. What
hinders application of such TE devices in extensively commercial usage, such as vehicles, is
probably their limited commercial viability and thermal stability; this restricts their utilization to
relatively specific niches such as power generation for deep space missions.
The Technion Thermoelectric Materials Research Group focuses on two classes of bulk TE
materials, namely chalcogenide and metal-oxide based compounds; whereas the first one
provides solutions for highly-efficient energy conversion at the mid-range temperatures, the
second one is characterized by high chemical stability and inexpensive energy conversion at
elevated temperatures.
In this talk we will introduce strategies to develop TE materials with improved properties, which
are based on experimental procedures mostly, incl. materials synthesis, TE transport property
measurements, and high-resolution electron microscopy, and are supplemented by density
functional theory (DFT) calculations. We will show how controlled nucleation and growth of
second-phase precipitates in PbTe-based compounds result in scattering of heat-carrying
phonons, thereby reducing thermal conductivity and improving TE performance. Evaluation of
the growth and coarsening rates of Ag-rich precipitates in PbTe requires quantitative information
on the bulk diffusion of Ag in PbTe-matrix. To this end, we apply DFT calculations of the Ag-
diffusant’s vibrational frequencies and its activation energy for diffusion, which enables us to
derive the temperature-dependent diffusion coefficients. Furthermore, DFT calculations of point
defect energies, electronic density of states, and spatial charge distribution indicate that
interstitial diffusion is the governing mechanism, and is preferred compared to the vacancy
mechanism. We will also show how selective doping of CaO(CaMnO 3 ) m -based compounds at
preferred lattice sites enables us manipulating the energy barriers for charge carrier transport,
thereby enhancing their TE power factor.
These two selected case studies exemplify the use of computational tools to address fundamental
materials-science oriented issues that are involved in the design of TE materials.