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Bismuth telluride-based materials are well known for their excellent thermoelectric (TE) properties within the near-room temperature range. However, the poor thermoelectric performance of their n-type counterparts has posed a major hindrance to the application of bismuth telluride-based thermoelectric generator (TEG). In this study, a dual optimization approach was implemented. Specifically, 2D ceramic nano-sized hexagonal boron nitride (h-BN) was introduced into n-type Bi 2 Te 2.7 Se 0.3 (BTS) to enhance its performance, aligning it with p-type materials. It is indicated that ceramic h-BN decoration leads to the emergence of a high density of dislocations, which boosts the phonon scattering and reduces lattice thermal conductivity significantly. Meanwhile, a high carrier mobility is maintained to ensure an improved power factor. With the addition of moderate ceramic h-BN, the composite material achieved a ZT value of 1.1 at 400 K. The geometric configuration of TEG was optimized using finite element methods to strike the optimal balance between output power (P o u t ) and efficiency (η). Based on the structure optimization results, the predicted P o u t and η increased by 48 % and 36 %, respectively. The fabricated TEG demonstrated to achieve an efficiency of 6.4 %. This work allows the evolution from bismuth telluride-based prototype to a functional TEG advanced in room-temperature heat recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • The single-phase structure of Fe 0.1 Co 0.8 Ni 0.1 S 2 was successfully prepared by doping Fe and Ni in CoS 2 by solid phase method. • Fe 0.1 Co 0.8 Ni 0.1 S 2 has excellent discharge performance as a positive electrode material for thermal batteries. • The mechanism of enhancing the electrochemical performance of CoS2 by doping was revealed. • There is a synergistic effect between Fe, Ni and Co. CoS 2 can meet the strict requirements of high probability output capacity and high energy output capacity of thermal batteries in modern weaponry thanks to its advantages of low resistivity and high thermal decomposition temperature combined with a full Li+ conductive electrolyte. Nevertheless, CoS 2 has the limitations of a low voltage platform and theorical capacity. In this case, Fe and Ni are doped into the CoS 2 lattice through low-temperature solid-phase sintering to synthesize Fe 0.1 Co 0.8 Ni 0.1 S 2 with a single-phase structure. Fe 0.1 Co 0.8 Ni 0.1 S 2 generated by the solid phase method has higher thermal stability, which can reduce the high temperature thermal shock at the immediate start of the thermal battery and assure the safety of the thermal battery in operation. Meanwhile, the mass loss of Fe 0.1 Co 0.8 Ni 0.1 S 2 at 615 °C is only 5 %, allowing it to discharge at the maximum effective mass at the normal operating temperature(∼500 °C). Because of the synergistic action of Fe2+, Ni2+, and Co2+ in the discharge process, the discharge voltage of CoS 2 increases significantly, giving CoS 2 higher specific energy. The simultaneous boost in specific energy and specific capacity indicates that doping has been highly successful in modifying CoS 2 , making CoS 2 more appropriate for the use of high current and long-life thermal cell systems. [ABSTRACT FROM AUTHOR]

BiCuSeO oxyselenides are promising thermoelectric materials because of their high stability and high thermoelectric performance. Here, a new approach is proposed that Li and Ca are incorporated into BiCuSeO to achieve synergistically optimized electrical and thermal transport properties. Arising from partial substitutions of Bi3+ by Ca2+ and Li+, the carrier concentration significantly increased because of massively introduced hole carriers. More importantly, we reveal that the carrier mobility can be enhanced by light element Li doping arising from largely reduced carrier scattering. The largest carrier mobility value reaches 8.06 cm2V−1s−1, which is significantly enhanced as compared with previously reported doped BiCuSeO. As a result, the electrical conductivity increases to 288 Scm−1 and the power factor reaches as high as 804 μW m−1K−2 at room temperature in Bi 0.84 Li 0.08 Ca 0.08 CuSeO, which is about 288 and 53 folds as compared with pristine BiCuSeO, respectively. Furthermore, Li and Ca codoping not only leads to dual-atomic point-defects scattering, but also can effectively scatter high-frequency phonons through introducing calcium oxide nanoprecipitates, resulting in a low lattice thermal conductivity (0.54 Wm−1K−1 at 873 K). The combination of optimized power factor and thermal conductivity contributes to a high thermoelectric figure of merit ZT (∼0.9 at 873 K) in Bi 0.88 Li 0.06 Ca 0.06 CuSeO. This study provides a new pathway for enhancing thermoelectric performance of BiCuSeO via light element doping and introducing nanostructures. • A high ZT of 0.9 is realized by light element doping and introducing nanostructures. • Light element Li doping is effective in improving carrier mobility and electrical conductivity. • Li and Ca codoping brings about a low lattice thermal conductivity because of CaO nanoparticles. [ABSTRACT FROM AUTHOR]

Interface engineering has been employed on commercial Bi 0.5 Sb 1.5 Te 3 (BST) to obtain synergistically enhanced thermoelectric performance via incorporating amorphous Sb 2 S 3 nano spheres. [Display omitted] • Conducting interface engineering via incorporating Sb 2 S 3 in Bi 0.5 Sb 1.5 Te 3. • Decoupling thermal and electrical properties via introducing Sb/BST interfaces. • Obtaining a high zT of ∼ 1.31 at 330 K in Bi 0.5 Sb 1.5 Te 3 -0.4%Sb 2 S 3. Tremendous efforts have been focusing on the improvement of p-type (Bi, Sb) 2 Te 3 -based thermoelectric materials for commercial applications. In this study, we achieve versatile interface engineering through a surface decoration of Bi 0.5 Sb 1.5 Te 3 by amorphous Sb 2 S 3 combining with spark plasma sintering, which introduces semi-coherent Sb/Bi 0.5 Sb 1.5 Te 3 interfaces and dopes S into Bi 0.5 Sb 1.5 Te 3. Semi-coherent Sb/Bi 0.5 Sb 1.5 Te 3 interfaces strongly scatter phonons and lower energy carriers, leading to decreased thermal conductivity and increased Seebeck coefficient, while the electrical conductivity is not sacrificed due to the compromise of the slightly reduced carrier mobility by interfacial scattering and the increased carrier concentration by S doping. Benefited from the decoupled thermoelectric properties, a significantly enhanced power factor of 3345.40 μW m−1 K−2 and a low thermal conductivity of 0.78 W m−1 K−1 is obtained in Bi 0.5 Sb 1.5 Te 3 -0.4%Sb 2 S 3 , leading to a high peak zT of ∼ 1.31 at 330 K, which shows a 54% enhancement compared with pristine Bi 0.5 Sb 1.5 Te 3. Moreover, a conversion efficiency of ∼ 7.6% can be predicted in a single leg Bi 0.5 Sb 1.5 Te 3 -0.4%Sb 2 S 3 -based module under a cold side temperature of 300 K and hot side temperature of 480 K. This study paves a facile amorphous Sb 2 S 3 induced interface engineering strategy for the development of high performance (Bi,Sb) 2 Te 3 -based thermoelectric materials. [ABSTRACT FROM AUTHOR]

• This work possesses a high ZT ave of 1.23 by nano-TiC ceramic incorporation. • The electron and phonon transport properties are synergistically manipulated. • The samples exhibit excellent improvement in Knoop harness. Bismuth antimony telluride (BiSbTe) composites are the most studied thermoelectric materials around room temperature. However, the extension of commercial applications is mostly restricted by its inferior conversion efficiency and mechanical stability. In this work, we report that the introduction of nano-sized ceramic titanium carbide (nano-TiC) can achieve a high dimensionless figure of merit (ZT) value up to 1.3 at 400 K and an increment in hardness over 37.93% at room temperature in Bi 0.3 Sb 1.7 Te 3 (BST) composites. On one hand, nano-TiC creates BST/TiC interfaces so that total thermal conductivity is reduced. Meanwhile, the Seebeck coefficient increases due to the scattering of carriers through the TiC-driven energy filtering effect. On the other hand, the hardness increases substantially with the addition of TiC resulted from the pinning effect induced hardening by grain boundaries and secondary phases. The results indicate that nano-TiC dispersion into BST matrix is effective for the enhancement in both thermoelectric performance and mechanical properties, which is favorable to practical applications. Moreover, the method of introducing nano-sized ceramic materials can also be extended to other thermoelectric systems. [ABSTRACT FROM AUTHOR]

• Achieving texture-degree-control to control the thermoelectric performance of layered-structured materials. • Proposing that the texture degree of Bi 2 Te 3 -based materials should be properly designed. • Linking nanostructure engineering with texture engineering to manipulate the thermoelectric properties. In this study, Bi 2 Te 3 nanostructures were synthesized with controlled morphologies by using a solvothermal process and then sintered by spark plasma sintering to obtain bulk samples with controllable texture degrees. The sintered nanostructured Bi 2 Te 3 pellets show texture-dependent thermoelectric properties, in which their Seebeck coefficient, electrical conductivity and thermal conductivity can be optimized by the proper texture design to simultaneously secure a high carrier mobility and strong phonon scattering, resulting in a peak ZT value of ~0.69 at 333 K. This study reveals the potential of texture engineering in developing high performance anisotropic thermoelectric materials. [ABSTRACT FROM AUTHOR]

Lead telluride (PbTe) has long been considered as an ideal p -type thermoelectric material at an intermediate temperature range. However, the relatively low thermoelectric performance of n -type PbTe largely limits the commercial applications of integral PbTe devices. In current work, we report that a significant enhancement of the ZT value of ≈1.3 can be achieved at 823 K in PbTe 0.998 I 0.002 -0.5%C 60 by adding low-dimensional C 60 nanodots. This remarkable improvement in thermoelectric performance is attributed to the incorporation of C 60 in n -type PbTe matrix, which creates dense nanodots that can simultaneously manipulate electron and phonon transport. On one hand, the dispersion of C 60 nanodots in n -type PbTe matrix leads to highly depressed lattice thermal conductivity (κ lat) (∼52%) due to the refinement of grains and the extra phonon scattering centers. On the other hand, the introduction of C 60 nanodots increases the scattering parameter r x , and brings about the overall improvement of Seebeck coefficient S , especially at room temperature. This work demonstrates the great potential of low-dimensional dopant in optimizing PbTe thermoelectric materials, which should be equally applicable in improving the performance of other thermoelectric materials. • C 60 nanodots can simultaneously manipulate electron and phonon transport. • C 60 nanodots refines the grains to decrease the κ lat. • C 60 nanodots triggers additional scattering mechanisms to further reduce the κ lat. • The introduction of C 60 nanodots enhances the S by increasing the r x. • The C 60 -contained sample has a 45% enhancement in ZT maximum. [ABSTRACT FROM AUTHOR]

Ca 3 Co 4 O 9+δ ceramic is a potential p-type thermoelectric material for high temperature applications, however, its thermoelectric performance is limited by the strongly interrelated thermoelectric parameters. In this work, we develop an effective method to simultaneously tune the electrical and thermal transport properties of Ca 3 Co 4 O 9+δ. We firstly synthesize Ca 3 Co 4 O 9+δ powders and subsequently obtain surface modified Cu/Ca 3 Co 4 O 9+δ through a well-controlled electroless plating technique followed by a fast Spark Plasma Sintering process. The detailed characterizations of microstructures and chemical compositions of Cu/Ca 3 Co 4 O 9+δ samples suggest that the plated Cu has been doped into the Ca 3 Co 4 O 9+δ after sintering. The doped Cu substitutes Ca ions, creates local oxygen deficiency and increases the ratios of Co3+ and Co4+, which reduces the carrier concentration and induces Ca-missed regions, thus, reducing the electrical and thermal conductivity. This study indicates that introducing metallic Cu phase by chemical electroless technique is a promising method to tune the thermoelectric properties of Ca 3 Co 4 O 9+δ -based ceramics by altering the chemical composition and microstructures. Image 1 • The surface modified Cu/Ca 3 Co 4 O 9+δ composites are prepared with controlled Cu contents. • The plated Cu can be doped into Ca 3 Co 4 O 9+δ after sintering, changing the chemical composition and microstructure. • The Cu plating can simultaneously modify the electrical and thermal transport properties of Ca 3 Co 4 O 9+δ ceramics. [ABSTRACT FROM AUTHOR]