High-pressure synthesis of new filled skutterudite compounds SrT4As12 (T = Fe, Ru, Os)

We have succeeded in synthesizing samples of new filled skutterudite compounds SrT 4As12 (T = Fe, Ru, and Os) using a high-pressure synthesis technique. These compounds have lattice constants of 8.351, 8.521, and 8.561 Å, respectively. The physical properties of the compounds are reported for the first time. The temperature dependences of the electrical resistivity for SrT 4As12 (T = Fe, Ru, and Os) exhibit metallic behaviors. The electrical resistivity and magnetic measurements indicates that SrOs4As12 is a new superconductor with a transition temperature of 4.8 K. A broad maximum of magnetic susceptibility at around 50 K and a large electronic specific heat coefficient of 58 mJ mol−1 K−2 suggest that SrFe4As12 is a nearly ferromagnetic metal with spin fluctuations of Fe 3d electrons

High-pressure Synthesis and Bulk Modulus of Non-centrosymmetric Superconductor Mo3Al2C

Mo3Al2C is a superconductor without inversion symmetry (the transition temperature T C ~ 9K). We have succeeded in preparing high-quality samples of Mo3Al2C using the high-pressure synthesis technique. The samples were characterized by powder x-ray diffraction (XRD) analysis. Furthermore, powder XRD patterns for the samples with synchrotron radiation have been studied under high pressures up to around 10 GPa and the volume versus pressure curve for the compound has been investigated. A bulk modulus was estimated to be 221 GPa

The structural, transport, and magnetic properties of Yb-filled skutterudites YbyFexCo4−xSb12 synthesized under high pressure

The effects of Fe-substitution on partially Yb filled skutterudites YbyFexCo4-xSb12 are presented from the viewpoint of crystal structure and thermoelectric, magnetic, and transport properties. A series of polycrystalline n-type YbyFexCo4-xSb12 (0.21 ≤ y ≤ 0.47, 0 ≤ x ≤ 0.76) samples were prepared using a high-pressure and high-temperature method. X-ray diffraction data suggest that all the compounds are high-purity skutterudites. For the YbyFexCo4-xSb12 with Yb content higher than 0.29 and Fe content lower than 1, the lattice constant shows a saturated behavior despite the change in the Yb/Fe content. Rietveld refinement based on the synchrotron radiation X-ray data implies that the rectangular Sb4 ring is transformed into square with increasing Yb content and/or Fe substitution content. The Yb valence gradually decreases as the Fe content increases from magnetic susceptibility analysis. According to the specific heat analysis, higher Yb filling benefits the lower Debye temperature while the Fe substitution leads to an increased Debye temperature. The Einstein temperature decreased with increasing Yb filling fraction, but Fe substitution for the Co site does not change the Einstein temperature further. Fe-substitution causes the reduction of total thermal conductivity κ, which mainly originates from the decrease of electron thermal conductivity contribution. The resistivity, Seebeck coefficient, thermal conductivity, and figure of merit (ZT) were effectively tuned due to the optimization of the carrier concentration. At the same carrier concentration, the hall mobility was decreased by Fe substitution. The proper Fe substitution content (0.2 in Yb0.25Fe0.2Co3.8Sb12) can result in a relatively high effective mass

Suppression of ferromagnetic spin fluctuations in the filled skutterudite superconductor SrOs4As12 revealed by As-75 NMR-NQR measurements

Motivated by the recent observation of ferromagnetic spin correlations in the filled skutterudite SrFe4As12 [Q.-P. Ding et al., Phys. Rev. B 98, 155149 (2018)], we have carried out As-75 nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements to investigate the role of magnetic fluctuations in the newly discovered isostructural superconductor SrOs4As12 with a superconducting transition temperature of T-c similar to 4.8 K. Knight shift K determined by the NQR spectrum under a small magnetic field (<= 0.5 T) is nearly independent of temperature, consistent with the temperature dependence of the magnetic susceptibility. The nuclear spin-lattice relaxation rate divided by temperature, 1/T1T, is nearly independent of temperature above similar to 50 K and increases slightly with decreasing temperature below the temperature. The temperature dependence is reasonably explained by a simple model where a flat band structure with a small ledge near the Fermi energy is assumed. By comparing the present NMR data with those in SrFe4As12, we found that the values of vertical bar K vertical bar and 1/T1T in SrOs4As12 are smaller than those in SrFe4As12, indicating no obvious ferromagnetic spin correlations in SrOs4As12. From the temperature dependence of 1/T-1 in the superconducting state, an s-wave superconductivity is realized

Enhanced thermoelectric performance of optimized Yb-filled and Fe-substituted skutterudite compounds Yb0.6FexCo4−xSb12

Optimized Yb-filled Fe-substituted skutterudites Yb0.6Fe x Co4? x Sb12 (x = 0, 0.5, and 1.0) were synthesized using a high-pressure technique. The samples were characterized by powder X-ray diffraction (XRD) analysis and electron probe microanalysis (EPMA). The thermoelectric transport properties of the samples such as Seebeck coefficient, electrical conductivity, carrier concentration, and thermal conductivity were studied in the temperature range of 2?300 K. With 1/8 Fe substitution for the Co site (x = 0.5), the Seebeck coefficient and thermal conductivity were obviously optimized. Carrier concentration analysis indicates that proper Fe substitution can effectively compensate for the excess electrons and optimize the electric transport properties. The reduction in the total thermal conductivity κ could be mainly caused by the reduction in electron contribution to κ. Compared with an only-Yb-filled compound, a 26% improved figure of merit ZT was achieved at 300 K at the Fe substitution ratio x = 0.5 (ZT = 0.11). This result confirms that Fe substitution on the Co site is an effective approach to tuning and optimizing the thermoelectric properties of CoSb3-based skutterudites

Colorectal Carcinoma with Extremely Low CA19-9

Aim. The aim of this study is to determine the significance of postoperative sequential measurements of serum CA19-9 in patients with extremely low serum level. Patients and Methods. Serum level of CA19-9 of 1096 patients who underwent surgery was measured preoperatively and every three months after surgery for 5 years. Patients with CA19-9 level of less than 2 U/mL at the time of diagnosis were defined as Extremely Low CA19-9 (ELCA). Results. One hundred and seven patients (9.8%) were ELCA. Of these, 86 underwent surgery with curative intent. Serum levels of CA19-9 in patients who did not undergo curative resection (N = 12) and who developed recurrence (N = 10) were less than 2.0 U/mL in all occasions during followup. In all patients without recurrence, serum level of CA19-9 also remained less than 2.0 U/mL. Conclusion. In patients with extremely low CA19-9, who consist of 9.8% of colorectal carcinoma cases, postoperative sequential measurement of serum level of CA19-9 contributed neither to assessment of curability of surgical resection nor to detection of recurrence

Complexation of F⁻ by Li⁺ and Mg²⁺ Ions as Inorganic Anion Acceptors in Lactone-Based Li⁺/F⁻ and Mg²⁺/F⁻ Hybrid Electrolytes for Fluoride Shuttle Batteries

The development of high-quality fluoride-ion transporting electrolytes is a crucial demand for fluoride shuttle batteries (FSBs). However, the uncontrolled chemical and electrochemical activities of fluoride ions narrow the available potential window, hindering the development of high-voltage FSB cells. We present a method for upgrading recently developed lactone-based liquid fluoride electrolytes by complexation of F⁻ with Li⁺ and Mg²⁺ ions. In the resultant Li⁺/F⁻ and Mg²⁺/F⁻ hybrid electrolytes, Li2F+ and MgF+ were the most probable soluble complexes, and the effective fluoride concentrations could reach ∼0.15 M along with excess Li⁺(Mg²⁺) ions. Unique interactions between F⁻ and Li⁺(Mg²⁺) were observed using ¹⁹F nuclear magnetic resonance spectroscopy. Li⁺(Mg²⁺) ions thus served as inorganic anion acceptors with ultimate redox stabilities to expand the negative potential window of the electrolytes to near −3 V vs SHE. The proposed complex formation was also supported by a conductometric titration method. We demonstrated the superior and versatile electrochemical performances of the Li⁺/F⁻ hybrid electrolyte, which enabled reversible charge/discharge reactions of various metal electrodes and composite electrodes in a wide range of redox series. Further, the Li⁺/F⁻ hybrid electrolyte opened valid new reaction paths for aluminum, making it a promising negative electrode in high-voltage FSB cells

X-Ray Diffraction Study of CeT2Al10 (T = Ru, Os) at Low Temperatures and under Pressures

We have carried out a powder X-ray diffraction investigation on antiferromagnetic Kondo semiconductorsCeRu2Al10 and CeOs2Al10 at low temperatures and under high pressures as well as the structural investigationon single crystal of these compounds. The results of powder X-ray studies of CeRu2Al10 and CeOs2Al10 indicatethat these compounds do not have structural transition at its antiferromagnetic ordering temperature. The resultsof single crystal structural refinement indicate that the b-axis of this crystal structure is insensitive not only topressure but also to temperature and that the effect of cooling to Ce–Ce distance for CeRu2Al10 is the same asthat for CeOs2Al10