Language：English   Publisher：Functionally Graded Materials FORUM of Japan  

<p>A series of single crystalline Ba₈Cu<i>_x</i>Si_46-<i>_x</i> clathrate semiconductors with different Cu contents were successfully fabricated via Czochralski (CZ) method. The actual Cu content can increase with nominal Cu ratio, resulting in the higher values of Seebeck coefficient and electrical resistivity. Among the series, Ba_7.89Cu_4.66Si_41.34 sample shows a relatively high power factor of 0.688 mW/K² m at 500 °C. These results support that control of the Cu content leads to improvement of the power factor in Ba₈Cu<i>_x</i>Si_46-<i>_x</i> clathrate thermoelectric materials.<b> </b></p>

DOI： 10.14957/fgms.35.8

CiNii Research

Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Functionally Graded Materials FORUM of Japan  

<p>Chromium disilicide (CrSi₂) is generally known as a p-type degenerate semiconductor whose power factor can be improved by substitution of Al on the Si site. However, it has not been clarified why holes are majority carriers in pure CrSi₂ nor how the thermoelectric properties of CrSi₂₋<i>_x</i>Al<i>_x</i> depend on the temperature above 400 °C. In this paper, we prepared CrSi₂₋<i>_x</i>Al<i>_x</i> samples with <i>x</i> ranging from 0.00 to 0.20. The composition ratio in each sample measured by Wavelength-dispersive X-ray spectroscopy (WDX) showed that the sum of Si and Al to Cr was less than the stoichiometric ratio. The electronic density of states calculated by first principles calculation based on density functional theory revealed that the atomic vacancies on the Si sites, whose existence was implied by WDX, can supply holes. Comparing thermoelectric properties of the samples at 500 °C, the sample with nominal composition CrSi_1.96Al_0.04 showed the highest power factor 0.606 mW m⁻¹ K⁻².</p>

DOI： 10.14957/fgms.36.13

CiNii Research

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

A two-layer bulk Si material with different boron concentrations was prepared using spark plasma sintering to improve its thermoelectric performance by blocking minority carrier diffusion across its interfaces. The sintered two-layer sample (p⁺/p-Si) was cut to include the interface. Two monolayer samples (p⁺-Si, p-Si) were prepared for comparison. Seebeck coefficient mapping of the p⁺/p-Si surface by thermal probing confirmed a Seebeck coefficient gap between the two p-type Si layers, indicating that a band offset exists at the interface. When compared with the average resistivities and voltages for p⁺-Si and p-Si, the electrical resistivity in the p⁺/p-Si sample is almost identical, but the thermoelectric voltage is higher when the p⁺-part is heated more than the p-part. This indicates that bipolar carrier transport inhibition in the band offset improved the thermoelectric voltage. This bandgap engineering process and principle can be extended to other thermoelectric materials that can be processed via powder sintering.

DOI： 10.35848/1347-4065/ace4af

Web of Science

Scopus

Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/ace4af/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.inorgchem.2c01439

Web of Science

PubMed

Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Adsorption and photocatalytic decomposition behaviors of gas-phase acetaldehyde (CH CHO), together with carbon dioxide (CO ) formation have been measured for pure titania (TiO ) powders with three types of polymorphs (anatase, brookite, and rutile) under UV-light illumination, and assessed by a kinetic model that takes into account the immediate decomposition of CH CHO attached on the surface, and the gradual decomposition of CH CHO adsorbed on the surface. Experimental data are well reproduced by the present model, highlighting how adsorption-related pathways markedly contribute to overall CH CHO removal kinetics even for pure titanias. Although the initial removal rate depends on the surface area, which affects the adsorption capacity, it is suggested that specific surface area-based adsorbability and decomposition reactivity are enhanced by heightened crystallinity. Our kinetic analysis demonstrates that anatase exhibits the highest photocatalytic activity as a result of superior adsorbability, as well as superior decomposition reactivity, compared to other polymorphs. 3 2 2 3 3 3

DOI： 10.1016/j.cej.2020.125422

Web of Science

Scopus

Event date： 2022.10

Language：Japanese  

Venue：長崎県壱岐市   Country：Japan  

Event date： 2023.9

Presentation type：Oral presentation (general)  

Event date： 2023.9

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2023.9

Presentation type：Oral presentation (general)  

Venue：Kyoto Institute of Technology Matsugasaki Campus   Country：Japan  

Audience： High school students

Type：Lecture

女性研究者の研究活動紹介、質疑応答

Audience： High school students

Type：University open house

大学生活や研究活動について紹介すると共に、熱電材料についてのデモ実験や設備の解説を行った。

Audience： College students,　Graduate students,　Teachers,　Researchesrs,　General

Type：Other

学生時代の研究活動・研究室生活の経験に基づいて、後輩にあたる大学生・大学院生に向けての助言・勧めを含んだ講演を行った。また学内外からの参加者向けに、現在の研究活動の一端も紹介した。