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Open Access Research Article Issue
Superior multiphase interfaces in AgCuTe-based composite with significantly enhanced thermoelectric properties
Journal of Advanced Ceramics 2023, 12 (8): 1511-1520
Published: 14 July 2023
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It is common sense that a phase interface (or grain boundary) could be used to scatter phonons in thermoelectric (TE) materials, resulting in low thermal conductivity (κ). However, a large number of impurity phases are always so harmful to the transport of carriers that poor TE performance is obtained. Here, we demonstrate that numerous superior multiphase (AgCuTe, Ag2Te, copper telluride (Cu2Te and Cu2−xTe), and nickel telluride (NiTe)) interfaces with simultaneous strong phonon scattering and weak electron scattering could be realized in AgCuTe-based TE materials. Owing to the similar chemical bonds in these phases, the depletion region at phase interfaces, which acts as carrier scattering centers, could be ignored. Therefore, the power factor (PF) is obviously enhanced from ~609 to ~832 μW·m−1·K−2, and κ is simultaneously decreased from ~0.52 to ~0.43 W·m−1·K−1 at 636 K. Finally, a peak figure of merit (zT) of ~1.23 at 636 K and an average zT (zTavg) of ~1.12 in the temperature range of 523–623 K are achieved, which are one of the best values among the AgCuTe-based TE materials. This study could provide new guidance to enhance the performance by designing superior multiphase interfaces in the TE materials.

Open Access Research Article Issue
Constructed TiO2/WO3 heterojunction with strengthened nano-trees structure for highly stable electrochromic energy storage device
Journal of Advanced Ceramics 2023, 12 (3): 634-648
Published: 15 February 2023
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Tungsten trioxide (WO3) has been widely regarded as a prospective bifunctional material due to its electrochromic and pseudocapacitive properties, while still facing the dilemma of inadequate cycle stability and trapping-induced degradation. Here, inspired by the trees-strengthening approach, a unique titanium dioxide (TiO2) nanorod arrays strengthened WO3 nano-trees (TWNTs) heterojunction was rationally designed and constructed. In sharp contrast to the transmittance modulation (ΔT) attenuation of primary WO3 nano-trees during cycling, the TWNTs film showed not only excellent electrochromic performance but also fascinating cycle stability (77.35% retention of the initial ΔT after 10,000 cycles). Besides, the trapping-induced degradation could be easily rejuvenated by a potentiostatic de-trapping process. An electrochromic energy storage device (EESD) was further assembled based on the TWNTs film to deliver excellent ΔT (up to 79.5% at 633 nm), fast switching speed (tc/tb =1.9 s/14.8 s), extremely high coloration efficiency value (443.4 cm2·C−1), and long-term cycle stability (over 10,000 charge/discharge cycles). This innovative study provided in-depth insights into the electrochromism nature and a significant step in the realization of stable electrochromic-energy storage application, paving the way for multifunctional smart windows as well as next-generation optoelectronic devices.

Open Access Research Article Issue
Thermoelectric enhancement of p-type Si80Ge20 alloy via co-compositing of dual oxides: Respective regulation for power factor and thermal conductivity by β-Ga2O3 and SiO2 aerogel powders
Journal of Advanced Ceramics 2023, 12 (2): 228-241
Published: 10 January 2023
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Si-based thermoelectric (TE) materials are exhibiting remarkable perspectives in self-energized applications with their special advantages. However, the relatively high total thermal conductivity (κ) prevents their TE enhancement. Here, a strategy of co-compositing dual oxides was implemented for enhancing the TE properties of p-type Si80Ge20 bulks. Composited Ga2O3 was demonstrated to enhance the power factor (PF) due to the crystallization-induced effect of produced Ga by decomposition on SiGe matrix. Associating with compositing SiO2 aerogel (a-SiO2) powder, not only introduced the fine amorphous inclusions and decreased the grain size of host matrix, but also various nano morphologies were formed, i.e., nano inclusions, precipitations, twin boundaries (TBs), and faults. Combining with the eutectic Ge, hierarchical scattering centers impeded the phonon transport comprehensively (decreasing the phonon group velocity ( va) and relaxation time) for reducing the lattice-induced thermal conductivity ( κl). As a result, a minimum κ of 2.38 W·m−1·K−1 was achieved, which is significantly dropped by 32.6% in contrast with that of the pristine counterpart. Ultimately, a maximal dimensionless figure of merit (ZT) of 0.9 was achieved at 600 ℃, which is better than those of most corresponding oxide-composited Si-based bulks.

Open Access Research Article Issue
Carrier and microstructure tuning for improving the thermoelectric properties of Ag8SnSe6 via introducing SnBr2
Journal of Advanced Ceramics 2022, 11 (7): 1144-1152
Published: 02 July 2022
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The argyrodite compounds ( A(12n)/mm+Bn+X62(Am+ = Li+, Cu+, and Ag+; Bn+ = Ga3+, Si4+, Ge4+, Sn4+, P5+, and As5+; and X2-= S2-, Se2-, or Te2-)) have attracted great attention as excellent thermoelectric (TE) materials due to their extremely low lattice thermal conductivity (κl). Among them, Ag8SnSe6-based TE materials have high potential for TE applications. However, the pristine Ag8SnSe6 materials have low carrier concentration (< 1017 cm-3), resulting in low power factors. In this study, a hydrothermal method was used to synthesize Ag8SnSe6 with high purity, and the introduction of SnBr2 into the pristine Ag8SnSe6 powders has been used to simultaneously increase the power factor and decrease the thermal conductivity (κ). On the one hand, a portion of the Br- ions acted as electrons to increase the carrier concentration, increasing the power factor to a value of ~698 μW·m-1·K-2 at 736 K. On the other hand, some of the dislocations and nanoprecipitates (SnBr2) were generated, resulting in a decrease of κl (~0.13 W·m-1·K-1) at 578 K. As a result, the zT value reaches ~1.42 at 735 K for the sample Ag8Sn1.03Se5.94Br0.06, nearly 30% enhancement in contrast with that of the pristine sample (~1.09). The strategy of synergistic manipulation of carrier concentration and microstructure by introducing halogen compounds could be applied to the argyrodite compounds to improve the TE properties.

Open Access Research Article Issue
Substantial thermoelectric enhancement achieved by manipulating the band structure and dislocations in Ag and La co-doped SnTe
Journal of Advanced Ceramics 2021, 10 (4): 860-870
Published: 05 August 2021
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Eco-friendly SnTe based thermoelectric materials are intensively studied recently as candidates to replace PbTe; yet the thermoelectric performance of SnTe is suppressed by its intrinsically high carrier concentration and high thermal conductivity. In this work, we confirm that the Ag and La co-doping can be applied to simultaneously enhance the power factor and reduce the thermal conductivity, contributing to a final promotion of figure of merit. On one hand, the carrier concentration and band offset between valence bands are concurrently reduced, promoting the power factor to a highest value of ~2436 μW·m-1·K-2 at 873 K. On the other hand, lots of dislocations (~3.16×107 mm-2) associated with impurity precipitates are generated, resulting in the decline of thermal conductivity to a minimum value of 1.87 W·m-1·K-1 at 873 K. As a result, a substantial thermoelectric performance enhancement up to zT ≈ 1.0 at 873 K is obtained for the sample Sn0.94Ag0.09La0.05Te, which is twice that of the pristine SnTe (zT ≈ 0.49 at 873 K). This strategy of synergistic manipulation of electronic band and microstructures via introducing rare earth elements could be applied to other systems to improve thermoelectric performance.

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