Fabrication of nanostructured non-stoichiometric TiO2-x by spark plasma sintering for enhancing its thermoelectric properties |
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| Affiliation: | 1. School of Intelligent Manufacturing, Chengdu Technological University, Chengdu, 610031, China;2. College of Mechanical Engineering & Graduate School, Chiba University, Chiba, 262-8522, Japan;3. Tokyo Metropolitan College of Industrial Technology, Tokyo, 116-8523, Japan;4. Chiba Industrial Technology Research Institute, Chiba, 264-0017, Japan;1. School of Mechanical Engineering, Shandong University of Technology, Zibo, 255000, China;2. School of Materials Science and Engineering, Shandong University of Technology, Zibo, 255000, China;3. Institute of Additive Manufacturing, Shandong University of Technology, Zibo, 255000, China;4. Shandong Industrial Ceramics Research & Design Institute Co., Ltd., Zibo, 255000, China;5. School of Chemistry and Chemical Engineering, Shandong University of Technology, Zibo, 255000, China;1. Technical University of Košice, Faculty of Materials, Metallurgy and Recycling, Institute of Metallurgy, Letná 9, 042 02, Košice, Slovakia;2. Institute of Materials Research - Slovak Academy of Sciences, Watsonova 47, 040 01, Košice, Slovakia;3. KERAG, s.r.o, Košice, Slovakia;1. Faculty of Chemistry, Southern Federal University, Rostov-on-Don, Russia;2. Southern Scientific Center of Russian Academy of Science, Rostov-on-Don, Russia;1. Graduate Program in Aerospace Engineering, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego, 1235 - Cidade Universitária, 50670-901, Recife, Brazil;2. Department of Mechanical Engineering, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego, 1235 - Cidade Universitária, 50740-550, Recife, Brazil;3. Graduate Program in Materials Science, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego, 1235 - Cidade Universitária, 50740-560, Recife, Brazil;4. Graduate Program in Chemistry, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego, 1235 - Cidade Universitária, 50740-560, Recife, Brazil;5. Department of Fundamental Chemistry, Universidade Federal de Pernambuco, Av. Jorn. Aníbal Fernandes, 1235 - Cidade Universitária, 50740-560, Recife, Brazil;1. State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China;2. School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, China;3. BGRIMM Magnetic Materials & Technology Co, Ltd, Beijing, 102600, China |
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| Abstract: | In this study, nanostructured non-stoichiometric TiO2-x compacts were prepared by the in-situ reduction of rutile titanium oxide (TiO2) powder with urea powder via spark plasma sintering (SPS). The crystal structure and particle size of the prepared compacts were examined. The XRD patterns revealed that TiO2 could be reduced easily by the urea powder to obtain non-stoichiometric TiO2-x, and the compacts still possessed rutile crystal structures. The average particle sizes of the compacts were less than 250 nm, successfully obtaining the non-stoichiometric TiO2-x with uniform nanostructures at the sintering temperature of 1073 K. In addition, nanostructured TiO2-x compacts with Magnéli phase TinO2n-1 (n = 2, 4, 8) were fabricated by varying the volume fraction of Ti powder in a urea environment via SPS. The results suggested that addition of Ti powder contributed to the formation of Magnéli phases TinO2n-1, and the value of n decreased with an increase in the volume fraction of the Ti powder. Furthermore, the thermoelectric properties of the compacts sintered with and without Ti powder were both investigated. The TiO2–U13.3-Ti10 compact displayed the highest power factor of 5.04 μWcm−1K−2 at 973 K. A lower thermal conductivity was achieved by TiO2–U13.3-Ti10 compact in the temperature range of 373–973 K, approximately 3 Wm−1K−1, due to the nanostructures and Magnéli phases. The highest ZT value of 0.146 was obtained for the TiO2–U13.3-Ti10 compact at 973 K, achieving a reasonable enhancement of thermoelectric properties. |
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| Keywords: | Nanostructures Spark plasma sintering Thermoelectric properties |
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