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Open Access Research Article Issue
Highly enhanced thermoelectric and mechanical performance of copper sulfides via natural mineral in-situ phase separation
Journal of Advanced Ceramics 2024, 13 (5): 641-651
Published: 28 May 2024
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In situ phase separation precipitates play an important role in enhancing the thermoelectric properties of copper sulfides by suppressing phonon transmission. In this study, Cu1.8S composites were fabricated by melting reactions and spark plasma sintering. The complex structures, namely, micron-PbS, Sb2S3, nano-FeS, and multiscale pores, originate from the introduction of FePb4Sb6S14 into the Cu1.8S matrix. Using effective element (Fe) doping and multiscale precipitates, the Cu1.8S+0.5 wt% FePb4Sb6S14 bulk composite reached a high dimensionless figure of merit (ZT) value of 1.1 at 773 K. Furthermore, the modulus obtained for this sample was approximately 40.27 GPa, which was higher than that of the pristine sample. This study provides a novel strategy for realizing heterovalent doping while forming various precipitates via in situ phase separation by natural minerals, which has been proven to be effective in improving the thermoelectric and mechanical performance of copper sulfides and is worth promoting in other thermoelectric systems.

Open Access Research Article Issue
High-entropy perovskite RETa3O9 ceramics for high-temperature environmental/thermal barrier coatings
Journal of Advanced Ceramics 2022, 11 (4): 556-569
Published: 17 March 2022
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Four high-entropy perovskite (HEP) RETa3O9 samples were fabricated via a spark plasma sintering (SPS) method, and the corresponding thermophysical properties and underlying mechanisms were investigated for environmental/thermal barrier coating (E/TBC) applications. The prepared samples maintained low thermal conductivity (1.50 W·m-1·K-1), high hardness (10 GPa), and an appropriate Young’s modulus (180 GPa), while the fracture toughness increased to 2.5 MPa·m1/2. Nanoindentation results showed the HEP ceramics had excellent mechanical properties and good component homogeneity. We analysed the influence of different parameters (the disorder parameters of the electronegativity, ionic radius, and atomic mass, as well as the tolerance factor) of A-site atoms on the thermal conductivity. Enhanced thermal expansion coefficients, combined with a high melting point and extraordinary phase stability, expanded the applications of the HEP RETa3O9. The results of this study had motivated a follow-up study on tantalate high-entropy ceramics with desirable properties.

Open Access Research Article Issue
Influence of HfO2 alloying effect on microstructure and thermal conductivity of HoTaO4 ceramics
Journal of Advanced Ceramics 2019, 8 (4): 537-544
Published: 04 December 2019
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HfO2 alloying effect has been applied to optimize thermal insulation performance of HoTaO4 ceramics. X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy are employed to decide the crystal structure. Scanning electronic microscopy is utilized to detect the influence of HfO2 alloying effect on microstructure. Current paper indicates that the same numbers of Ta5+ and Ho3+ ions of HoTaO4 are substituted by Hf4+ cations, and it is defined as alloying effect. No crystal structural transition is introduced by HfO2 alloying effect, and circular pores are produced in HoTaO4. HfO2 alloying effect is efficient in decreasing thermal conductivity of HoTaO4 and it is contributed to the differences of ionic radius and atomic weight between Hf4+ ions and host cations (Ta5+ and Ho3+). The least experimental thermal conductivity is 0.8 W·K-1·m-1 at 900 ℃, which is detected in 6 and 9 mol%-HfO2 HoTaO4 ceramics. The results imply that HfO2-HoTaO4 ceramics are promising thermal barrier coatings (TBCs) due to their extraordinary thermal insulation performance.

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