Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide TiO&lt;SUB&gt;2&amp;minus;&lt;I&gt;x&lt;/I&gt;&lt;/SUB&gt; Fabricated by Reduction Treatment Using Carbon Powder

Lu, Yun; Hirohashi, Mitsuji; Sato, Kenkichi

doi:10.2320/matertrans.47.1449

Cited by 62 publications

(31 citation statements)

References 26 publications

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“…When SPS temperature was 1373 K, the electrical resistivity at room temperature was only 1.52 ³ mm, which was lower than that (2.20 ³ mm) of the reduced TiO 2¹x at the same temperature in the previous work. 23) EPMA analysis for the composition of the compact fabricated by SPS at 1373 K is shown in Fig. 2.…”

Section: ¹3mentioning

confidence: 99%

“…5 and 6, respectively. For comparison, the data of the TiO 2¹x plate fabricated by reducing TiO 2 plate through reduction treatment using carbon powder in the previous work 23) are also shown in Figs. 5 and 6.…”

Section: Thermoelectric Properties Of Tio 2¹xmentioning

confidence: 99%

“…Recently, we have proposed a simple reduction process using carbon powder to reduce TiO 2 . 23) In the reduction process, non-stoichiometric titanium dioxide, TiO 2¹x was obtained through the reduction of TiO 2 in carbon powder at elevated temperatures and the thermoelectric properties of TiO 2¹x were noticeably improved.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Sagara

Hao

et al. 2012

Mater. Trans.

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To obtain non-stoichiometric titanium dioxide, TiO 2 powder was sintered in a graphite die by spark plasma sintering (SPS). The microstructure and the crystal type of the compacts were examined. Thermoelectric properties of the compacts were measured and discussed. The results revealed that TiO 2 could be easy to be reduced in the graphite die by SPS to obtain non-stoichiometric titanium dioxide, TiO 2¹x with uniform composition distribution. Electrical resistivity of the compacts decreased with increase of SPS temperature. Seebeck coefficient also decreased with increase of SPS temperature, but kept large absolute values over 300 µV·K ¹1. Therefore, the compacts fabricated by SPS showed relatively high thermoelectric performance. The power factor reached 5 © 10 ¹5 W m ¹1 K

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Section: ¹3mentioning

confidence: 99%

Section: Thermoelectric Properties Of Tio 2¹xmentioning

confidence: 99%

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Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Sagara

Hao

et al. 2012

Mater. Trans.

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“…10,11) It suggests the combination of SPS and the following reduction treatment is effective and feasible to improve the thermoelectric performance of TiO 2 . For the unpolished sample ( Fig.…”

Section: Thermoelectric Propertiesmentioning

confidence: 99%

“…10) In addition, we also prepared nonstoichiometric TiO 2¹x compact by spark plasma sintering (SPS) of TiO 2 in a graphite die.…”

Section: Introductionmentioning

confidence: 99%

Improvement in Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide by Reduction Treatment

Hao

Sagara

et al. 2013

Mater. Trans.

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Compacts of non-stoichiometric TiO 2¹x were fabricated by SPS and the following reduction treatment in carbon powder. XRD, SEM and EPMA were used to characterize the compacts. The results showed that they were composed of non-stoichiometric TiO 2¹x inside and TiO as the surface layer. The thickness of the surface layer was increased with the increase of the holding time and exceeded 100 µm when it came to 20 h. Carbon did not penetrate into the compacts during the reduction treatment. To examine the carrier density and the non-stoichiometric number, 2 ¹ x, thermogravimetry was carried out. The study showed that the value of 2 ¹ x was decreased and the carrier density was increased as the holding time increased. The thermoelectric properties including electrical resistivity, Seebeck coefficient and power factor was measured. The electric resistivity was considerably reduced by the reduction treatment. The values of the Seebeck coefficient was also decreased by the reduction treatment but maintained at a large absolute value of 250 µV·K ¹1 at 573 K. Power factor reached 2 © 10 ¹4 W·m ¹1 ·K ¹2 at 573 K. The value was much higher than that of the samples by SPS only. Therefore, the thermoelectric performance was improved by the reduction treatment. The influence of the TiO layer on the thermoelectric performance was also examined. It was believed that the influence should result from its comprehensive effect on Seebeck coefficient and electrical resistivity.

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Direct Laser Writing of Crystallized TiO₂ and TiO₂/Carbon Microstructures with Tunable Conductive Properties

Schrodj

Mougin

et al. 2018

Advanced Materials

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for use in conductors, semiconductors, and insulators. [5] Electronic properties are indeed closely linked to the nature of the metal and conditions of fabrication, which determine the structure of the final material at the atomic scale. These properties can be modified by doping with different metals, by adjusting the metal to oxygen stoichiometry or by generating an amorphous or crystal phase. [6][7][8][9] Today, integration of MOs as thin films, micropatterns or nanopatterns by convenient and simple means remains a major challenge for the fabrication of electronic and optoelectronic devices. MOs are commonly deposited as thin films by sputtering. Though the sputtered MOs usually exhibit better electrical properties due to the accurate control of the composition and defect concentration at the atomic scale, solution-based processes have gained much attention during the last years due to their simplicity, cost effectiveness, vacuum-free processes, and high versatility.In solution-based processes, thermal annealing is required to eliminate the solvent and organic ligands that are complexed on metal ions and to obtain material and phase compositions with suitable properties. This step is typically conducted at temperatures ranging from 300 to 1000 °C. Thus, such a fabrication strategy can be difficult to apply in the case of multistep integration processes involving different materials.In this context, laser processing of MOs presents many advantages due to the control of the laser-matter interaction in space and time. [9] Laser curing allows a fast treatment that can be confined to a limited volume by focusing the laser beam. Such a laserinduced effect leads to a much lower energy consumption with respect to that of thermal annealing. For example, a pulsed laser in the ultraviolet (UV) or near-infrared (NIR) range has been successfully used for the crystal growth of amorphous MO films [10,11] or the hydrothermal growth of MO nanostructures. [12,13] Recently, laser processing has also been introduced for the direct writing of MO microstructures. For this purpose, UV or deep-UV (DUV) wavelengths are usually used. At the molecular scale, the patterning proceeds according to the photodecomposition of the metal precursors complexed by organic molecules. Patterning can be obtained at room temperature down to the nanoscale using direct laser writing (DLW), but usually, a thermal post-treatment is needed to obtain an MO with suitable Metal oxides are an important class of materials for optoelectronic applications. In this context, developing simple and versatile processes for integrating these materials at the microscale and nanoscale has become increasingly important. One of the major remaining challenges is to control the microstructuration and electro-optical properties in a single step. It is shown here that near-infrared femtosecond laser irradiation can be successfully used to prepare amorphous or crystallized TiO 2 microstructures in a single step using a direct laser writing (DLW) approach from a TiO 2 precursor ...

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Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide TiO<SUB>2−<I>x</I></SUB> Fabricated by Reduction Treatment Using Carbon Powder

Cited by 62 publications

References 26 publications

Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Improvement in Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide by Reduction Treatment

Direct Laser Writing of Crystallized TiO₂ and TiO₂/Carbon Microstructures with Tunable Conductive Properties

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Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide TiO<SUB>2&minus;<I>x</I></SUB> Fabricated by Reduction Treatment Using Carbon Powder

Cited by 62 publications

References 26 publications

Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Fabrication of Non-Stoichiometric Titanium Dioxide by Spark Plasma Sintering and Its Thermoelectric Properties

Improvement in Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide by Reduction Treatment

Direct Laser Writing of Crystallized TiO2 and TiO2/Carbon Microstructures with Tunable Conductive Properties

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Resources

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Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide TiO<SUB>2−<I>x</I></SUB> Fabricated by Reduction Treatment Using Carbon Powder

Direct Laser Writing of Crystallized TiO₂ and TiO₂/Carbon Microstructures with Tunable Conductive Properties