Significant Enhancement in the Thermoelectric Performance of a Bismuth Telluride Nanocompound through Brief Fabrication Procedures

A binary BiTe nanocompound for thermoelectric applications was prepared via a water-based chemical reaction under atmospheric conditions. We attempted to increase the carrier mobility of the nanocompound by adopting a post-thermal treatment consisting of calcination and reduction at different temperatures. We also tried to control the carrier density of the compound by adjusting the stoichiometry of the atomic constituents. We measured other transport properties (i.e., electrical resistivity, Seebeck coefficient, and thermal conductivity) and observed how these properties were affected by both the carrier mobility and the carrier density. We derived the thermoelectric performance, as captured by the figure of merit (ZT), from the transport properties and discussed the effect of such properties on the ZT value. The nanocompound exhibited a very competent ZT value (0.91 at 100 °C), which is one of the best thermoelectric performances of chemically synthesized BiTe materials

Investigation of Reaction Mechanisms of Bismuth Tellurium Selenide Nanomaterials for Simple Reaction Manipulation Causing Effective Adjustment of Thermoelectric Properties

We synthesized ternary n-type bismuth tellurium selenide nanomaterials for thermoelectric applications via a water-based chemical reaction under an atmospheric environment. In this work, bismuth nitrate was employed as a bismuth precursor and was hydrolyzed to form bismuth hydroxide in an aqueous solution. Ascorbic acid was used to dissolve the bismuth hydroxide and give a reactive bismuth source (Bi³⁺ ions) that was able to react with anion sources (Te^2–/Se^2– ions). Ascorbic acid played a role in reducing bismuth hydroxide to an unreactive bismuth source (bismuth particles, Bi⁰). We confirmed that ascorbic acid dissolved or reduced bismuth hydroxide depending on the solution pH. Because either Bi³⁺ ions or bismuth particles were generated depending on the pH, the nanomaterial stoichiometry was pH dependent. Nanomaterials prepared at various pH levels were individually sintered using a spark plasma sintering process to measure their thermoelectric transport properties (i.e., carrier concentration, electrical resistivity, Seebeck coefficient, and thermal conductivity). We observed how the transport properties were affected through adjustment of the pH of the reaction and found an appropriate pH for optimizing the transport properties, which resulted in enhancement of the thermoelectric performance

The pipeline of the plant phenotyping system.

<p>The pipeline of the plant phenotyping system.</p

Top-view images.

<p>A: Estimation of tray edge coordinates. B: A cropped single-pot image.</p

Superpixel images.

<p>Superpixel images.</p

Top-view images.

<p>A: Top-view original tray images using color marker detection. B: The warped image based on the color markers.</p

A validation dataset (left) and a test dataset (right).

<p>A validation dataset (left) and a test dataset (right).</p

Top view of a tray showing pot labeling.

<p>Top view of a tray showing pot labeling.</p

Plant-growth visualization; tracking plant area over time.

<p>Plant-growth visualization; tracking plant area over time.</p

Precision-recall curves of the three classifiers.

<p>A: Precision-recall curves of validation data sets. B: Precision-recall curves of test data sets.</p