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1. Multiprinter Additive Manufacturing of Flexible and Lightweight Thermoelectric Energy Harvesters Using Colloidal Nanoparticles

   Varghese, Tony; Weltner, Ariel; Manzi, Jacob; Hill, Curtis; Subbaraman, Harish; Estrada, David (August 2021, The 10th annual International Space Station Research and Development Conference (ISSRDC))

   Thermoelectric generators are being used as a successful power sources for space applications since 1960's in radioisotope-thermoelectric generators (RTGs) to supply power to space systems in deep space. RTG’s are capable of directly converting heat energy to uninterrupted electric power with no moving parts involved. The ability of thermoelectric materials to convert heat energy to electrical energy is defined by a dimensionless value known as the thermoelectric figure of merit (ZT) 1. This value quantifies the maximum thermoelectric efficiency of a thermoelectric generator (TEG) and is calculated by ZT= S2σT/κ, where S, σ, T, and κ represent Seebeck coefficient, electrical conductivity, temperature, and thermal conductivity, respectively. Among all of the thermoelectric materials, Bi2Te3 and its alloys have been reported to have high ZT values for low temperature energy harvesting and are highly suitable for powering wearables and self-powering sensors2, 3. 

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2. Enhanced thermoelectric performance of F4-TCNQ doped FASnI ₃ thin films

   https://doi.org/10.1039/D0TA09329G  

   Zheng, Luyao; Zhu, Tao; Li, Yifan; Wu, Haodong; Yi, Chao; Zhu, Jiahua; Gong, Xiong (December 2020, Journal of Materials Chemistry A)

   null (Ed.)

   In the past decade, great efforts have been devoted to the development of organic–inorganic hybrid perovskites for achieving efficient photovoltaics, but less attention has been paid to their thermoelectric applications. In this study, for the first time, we report the thermoelectric performance of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) doped NH 2 CHNH 2 SnI 3 (FASnI 3 ) thin films. It is found that the electrical conductivities of the F4-TCNQ doped FASnI 3 thin films increase and then decrease along with increased doping levels of F4-TCNQ. Systematic studies indicate that enhanced electrical conductivities are attributed to the increased charge carrier concentrations and mobilities and superior film morphologies of the F4-TCNQ doped FASnI 3 thin films, and decreased electrical conductivities originate from the cracks and poor film morphology of the F4-TCNQ doped FASnI 3 thin films induced by excess F4-TCNQ dopants. The quantitative thermal conductivity scanning thermal microscopy studies reveal that the F4-TCNQ doped FASnI 3 thin films exhibit ultralow thermal conductivities. Moreover, the thermoelectric performance of the F4-TCNQ doped FASnI 3 thin films is investigated. It is found that the F4-TCNQ doped FASnI 3 thin films exhibit a Seebeck coefficient of ∼310 μV K −1 , a power factor of ∼130 μW m −1 K −2 and a ZT value of ∼0.19 at room temperature. All these results demonstrate that our studies open a door for exploring cost-effective less-toxic organic–inorganic hybrid perovskites in heat-to-electricity conversion applications at room temperature. 

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3. Thermal analysis of thermoelectric active cooling including external thermal resistances

   https://doi.org/10.1063/5.0176286  

   Marquez_Peraca, Nicolas; Zhu, Qing; Kono, Junichiro; Wehmeyer, Geoff (December 2023, Applied Physics Letters)

   Thermoelectric active cooling uses nontraditional thermoelectric materials with high thermal conductivity, high thermoelectric power factor, and relatively low figure of merit (ZT) to transfer large heat flows from a hot object to a cold heat sink. However, prior studies have not considered the influence of external thermal resistances associated with the heat sinks or contacts, making it difficult to design active cooling thermal systems or compare the use of low-ZT and high-ZT materials. Here, we perform a non-dimensionalized analysis of thermoelectric active cooling under forced heat flow boundary conditions, including arbitrary external thermal resistances. We identify the optimal electrical currents to minimize the heat source temperature and find the crossover heat flows at which low-ZT active cooling leads to lower source temperatures than high-ZT and even ZT→+∞ thermoelectric refrigeration. These optimal parameters are insensitive to the thermal resistance between the heat source and thermoelectric materials, but depend strongly on the heat sink thermal resistance. Finally, we map the boundaries where active cooling yields lower source temperatures than thermoelectric refrigeration. For currently considered active cooling materials, active cooling with ZT < 0.1 is advantageous compared to ZT→+∞ refrigeration for dimensionless heat sink thermal conductances larger than 15 and dimensionless source powers between 1 and 100. Thus, our results motivate further investigation of system-level thermoelectric active cooling for applications in electronics thermal management. 

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4. Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films

   https://doi.org/10.1038/s41563-018-0059-8  

   Pandya, Shishir; Wilbur, Joshua; Kim, Jieun; Gao, Ran; Dasgupta, Arvind; Dames, Chris; Martin, Lane W. (April 2018, Nature Materials)

   The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3. Electric-field-driven enhancement of the pyroelectric response (as large as − 550 μC m−2 K−1) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert lowgrade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm−3, 526 W cm−3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting. 

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5. Data from: Advancing the Ca14AlSb11 structure type: Synthesis and characterization of Yb14CdSb11 for thermoelectric applications

   https://doi.org/10.5061/dryad.9w0vt4brw  

   Kauzlarich, Susan; Opara, Ivan (January 2025, Dryad)

   Abstract: The ternary phase Yb14CdSb11 has been synthesized using both flux and polycrystalline methods. The crystal structure was determined via single-crystal X-ray diffraction, revealing that it crystallizes in the Ca14AlSb11 structure type (I41/acd space group with unit cell parameters of a = 16.5962(2) Å and c = 22.1346(5) Å, 90 K, Z = 8, R1 = 2.65 %: wR2 = 4.58 %. The polycrystalline form of the compound was synthesized from a stoichiometric reaction of Yb4Sb3, CdSb, Yb, and Sb. The elemental composition was confirmed using scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), and phase purity was verified by powder X-ray diffraction (PXRD). Thermoelectric measurements, including resistivity, Seebeck coefficient, thermal conductivity, Hall carrier concentration, and Hall mobility, were conducted from 300 to 1273 K. Yb14CdSb11 exhibited a peak zT = 0.80 at 1150 K. Carrier concentration and Hall mobility ranged from to  holescm^-3^ and from 1019 cm²V-¹s-^¹, respectively. This carrier concentration is lower than that reported for the Zn or Mn analogs, leading to a lower thermoelectric figure of merit at high temperatures. However, with appropriate doping, it is expected that this phase should also be a promising p-type candidate for high-temperature energy conversion applications. TechnicalInfo: # Data from: Advancing the Ca14AlSb11 structure type: Synthesis and characterization of Yb14CdSb11 for thermoelectric applications ## Description of the data and file structure ### Files and variables #### File: Dryad_PXRD_data.zip **Description:**  Heat capacity, powder x-ray diffraction data for CdSb, Yb4Sb3, and Yb14CdSb11, carrier concentration, mobility, electrical resistivity, Seebeck coefficients, thermal conductivity, and zT for Yb14CdSb11. The zip file entitled Yb14CdSb11_All_Data.zip includes data files with Heat Capacity ("Heat capacity_YbCdSb.dat"), Powder X-ray Diffraction data of the binary precursors ("PXRD CdSb.txt", "PXRD Yb4Sb3.txt", and "PXRD_Yb14CdSb11.txt", and Thermoelectric transport data. **Heat Capacity** Heat capacity measurements of a single crystal were done in a Quantum Design PPMS from 2 K to 300 K. **Powder X-ray Diffraction (PXRD)** PXRD data were collected on each sample using a Bruker zero background holder on a Bruker D8 Eco Advanced employing Cu K∝ radiation (λ = 1.54 Å) with a Ni filter to remove Cu Kβ. **Seebeck Coefficient and Electrical Resistivity** Seebeck, resistivity, and Hall data were collected as a function of temperature under high vacuum at the Jet Propulsion Laboratory (JPL). Resistivity and Hall Van der Pauw measurements were performed with a current of 100 mA and a 0.8 T magnet. Seebeck coefficient was measured using a custom two-probe instrument under a high vacuum. Temperature-dependent Seebeck coefficients, electrical resistivity, and thermal conductivity were fit to six-order polynomials to calculate* zT* values. T (K):** **Temperature in Kelvin; r-fit (mΩ·cm): electrical resistivity; S-fit (µV/K): Seebeck coefficient; L- Lorenz number; K-fit: total thermal conductivity; K_e: electronic thermal conductivity; K_L: lattice (phonon) thermal conductivity; PF: power factor; ZT (dimensionless): thermoelectric figure of merit. **Thermal Conductivity** Thermal diffusivity was measured on densified pellets using laser flash analysis on a Netzsch LFA 475 Microflash under Ar(g) flow. The fully densified pellet was sliced into a thin disk (<1.5 mm) and polished until flat with parallel sides. The density of this disk was measured using Archimedes' method with toluene as the liquid. The heat capacity of Yb14CdSb11 was estimated using an adjusted heat capacity, Cp, based on the experimental heat capacity for Yb14MnSb11 and adjusting for the molecular weight of the Yb14CdSb11 analog: Where MM is the molar mass of the respective compounds. This adjusted heat capacity was employed to give the total thermal conductivity according to the equation: κ = D × Cp × *d* (D = measured diffusivity; Cp = heat capacity adjusted; *d* = the temperature-adjusted density).  The coefficient of thermal expansion (CTE) measured for Yb14MnSb11 was also employed. This procedure is consistent with past practice for compounds with the Yb14MSb11, compared to previously published work. 

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