Stabilization and high thermoelectric performance of high-entropy-type cubic AgBi(S, Se, Te)2

As thermoelectric generators can convert waste heat into electricity, they play an important role in energy harvesting. The metal chalcogenide AgBiSe2 is one of the high-performance thermoelectric materials with low lattice thermal conductivity (klat), but it exhibits temperature-dependent crystal structural transitions from hexagonal to rhombohedral, and finally a cubic phase as the temperature rises. The high figure-of-merit ZT is obtained only for the high-temperature cubic phase. In this study, we utilized the high-entropy-alloy (HEA) concept for AgBiSe2 to stabilize the cubic phase throughout the entire temperature range with enhanced thermoelectric performance. We synthesized high-entropy-type AgBiSe2-2xSxTex bulk polycrystals and realized the stabilization of the cubic phase from room temperature to 800 K for x > 0.6. The ultra-low klat at of 0.30 Wm^-1K^-1 and the high peak ZT 0.9 at around 750 K were realized for cubic AgBiSe2-2xSxTex without carrier tuning. In addition, the average ZT value of x = 0.6 and 0.7 for the temperature range of 360-750 K increased to 0.38 and 0.40, respectively, which are comparable to the highest previously reported values.Comment: 44 pages, 8 figure

Synthesis, structure and photocatalytic activity of layered LaOInS2

Indium oxychalcogenides would be attractive semiconductors considering the practical use of indium oxides and sulfides such as indium-tin oxides (ITO) and copper-indium-gallium diselenides (CIGS). In this work, a novel layered indium oxysulfide, LaOInS2, was synthesized by a metathesis reaction between LaOCl and NaInS2. Synchrotron X-ray diffraction showed that LaOInS2 consisted of alternately stacked rocksalt-type In-S and PbO-type La-O layers. The InS6 octahedron had split In sites with abnormally large anisotropic atomic displacement factors. LaOInS2 was found to be a direct semiconductor. Density functional theory calculations exhibited well-dispersed bands composed of In 5s/5p and S 3p/O 2p orbitals with a band gap of similar to 2.4 eV, which was close to the experimental value estimated by optical absorption (2.64 eV). Under visible light irradiation this visible-light absorption, LaOInS2 exhibited photocatalytic activity for H-2 and O-2 evolution from water with the aid of Pt and IrO2 cocatalysts, respectively

CCQM-K124 Trace elements and ehromium speciation in drinking water : Part A: Trace elements in drinking water Part B: chromium speciation in drinking water. Final report

CCQM-K124 was an activity of the Inorganic Analysis Working Group (IAWG) and was jointly coordinated by the National Metrology Institute of Japan (NMIJ) and the Government Laboratory, Hong Kong SAR (GLHK). The Part A of CCQM-K124 was organized by NMIJ and trace elements in drinking water were the measurands. The Part A of the key comparison was undertaken for NMIs and DIs to demonstrate their capabilities in measuring part-per-billion level (in μg/kg) or part-per-million level (in mg/kg) of trace elements in drinking water. It should also facilitate the acquisition of claims in Calibration and Measurement Capabilities (CMCs) as listed in Appendix C of Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee of Weights and Measures (CIPM MRA). Results were submitted by 14 NMIs and nine DIs. The participants used different measurement methods, though most of them used direct measurement using inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS) and high resolution ICP-MS and isotope dilution technique with ICP-MS. Other methods were graphite furnace atomic absorption spectrophotometry (GFAAS) and flame atomic absorption spectrophotometry (FAAS). The results of B, Ca, Cr, As and Cd show good agreement except some outliers. Concerning Hg, instability was observed when the sample was stored in the light. And some participants observed instability of Mo. Therefore, it was agreed to abandon the Hg and Mo analysis as this sample was not satisfactory for KC. Accounting for relative expanded uncertainty, comparability of measurement results for each of B, Ca, Cr, As and Cd was successfully demonstrated by the participating NMIs or DIs. Furthermore, the results of this key comparison can be utilized along with the IAWG core capability approach. It is expected that arsenic, boron, cadmium, calcium and chromium at mass fractions greater than approximately 0.1 µg/kg, 1 µg/kg, 0.01 µg/kg, 1 mg/kg and 0.1 µg/kg respectively in drinking water and similar matrices (groundwater and river water etc.) can be determined by each participant using the same technique(s) employed for this key comparison to achieve similar uncertainties mentioned in the present report