RESUMEN
The combination of laser ablation and inductively coupled plasma mass spectrometry (LA-ICP-MS) offers a powerful tool for directly analyzing solid samples. However, LA-ICP-MS has a limitation in quantitative analyses owing to a requirement for matrix-matched standard materials. In this study, we have developed a sample preparation method that facilitates quantitative analyses by LA-ICP-MS. The sample powder is dispersed in a liquid resin and film-like samples are prepared from the resulting paste by a screen-printing technique. The sample includes the analyte spiked with internal standards and is prepared by mixing standard solutions in the sample paste. Because all reagents except for the sample powder are liquids, homogeneous samples can be easily obtained. The internal standard and concentration of the spiked analyte can be tailored for each sample, which is a requirement for accurate quantitative analyses. The amount of sample and concentration of the spiked analyte are controlled against an internal standard, enabling internal standardization without the need to have an element of known concentration in the sample. The accuracy of this method was evaluated by analyzing impurity elements in TiO2 powder; however, it is expected that other materials could also be analyzed. The versatility and flexibility of this method suggest great potential for quantitative analyses by LA-ICP-MS, for which reliable matrix-matched standard materials are required.
RESUMEN
Nonreciprocal or even-order nonlinear responses in symmetry-broken systems are powerful probes of emergent properties in quantum materials, including superconductors, magnets, and topological materials. Recently, vortex matter has been recognized as a key ingredient of giant nonlinear responses in superconductors with broken inversion symmetry. However, nonlinear effects have been probed as excess voltage only under broken time-reversal symmetry. In this study, we report second harmonic transport under time-reversal symmetry in the noncentrosymmetric trigonal superconductor PbTaSe2. The magnitude of anomalous nonlinear transport is two orders of magnitude larger than those in the normal state, and the directional dependence of nonlinear signals are fully consistent with crystal symmetry. The enhanced nonlinearity is semiquantitatively explained by the asymmetric Hall effect of vortex-antivortex string pairs in noncentrosymmetric systems. This study enriches the literature on nonlinear phenomena by elucidating quantum transport in noncentrosymmetric superconductors.
RESUMEN
To improve thermoelectric performance of materials, the utilization of low-dimensional materials with a multi-alloy system is a promising approach. We report on the enhanced thermoelectric properties of n-type Bi2(SexTe1-x)3 nanoplates using solvothermal synthesis by tuning the composition of selenium (Se). Variation of the Se composition within nanoplates is demonstrated using X-ray diffraction and electron probe microanalysis. The calculated lattice parameters closely followed Vegard's law. However, when the Se composition was extremely high, an impurity phase was observed. At a reduced Se composition, regular-hexagonal-shaped nanoplates with a size of approximately 500 nm were produced. When the Se composition was increased, the shape distribution became random with sizes more than 5 µm. To measure the thermoelectric properties, nanoplate thin films (NPTs) were formed on a flexible substrate using drop-casting, followed by thermal annealing. The resulting NPTs sufficiently adhered to the substrate during the bending condition. The electrical conductivity of the NPTs increased with an increase in the Se composition, but it rapidly decreased at an extremely high Se composition because of the presence of the impurity phase. As a result, the Bi2(SexTe1-x)3 NPTs exhibited the highest power factor of 4.1 µW/(cmâK2) at a Se composition of x = 0.75. Therefore, it was demonstrated that the thermoelectric performance of Bi2(SexTe1-x)3 nanoplates can be improved by tuning the Se composition.