New filled skutterudite phosphides with heavy lanthanide (including Y), LnT4P12 (Ln = heavy lanthanide and Y; T = Fe, Ru and Os) have systematically been prepared at high temperatures and high pressures. The new relationship between lattice constants and atomic numbers of lanthanides was obtained for filled skutterudite phosphides. Electrical and magnetic properties of the skutterudites with heavy lanthanide have been studied at low temperatures. The superconductivity, the paramagnetic behavior, ferromagnetic and antiferromagnetic transitions were found for the new filled skutterudites prepared at high pressure. Thus, these compounds are classified to four groups by their magnetic properties. The physical properties of new filled skutterudite phosphides with heavy lanthanide (including Y) are discussed.
For the filled skutterudite compounds, high-pressure synthesis is thought to be a powerful technique, because it is possible to synthesize compounds that could not been grown by the flux method under ambient pressure and to improve the filling factor of rare-earth ions. In this article, we report the details of high-pressure synthesis of the filled skutterudite PrFe4Sb12 and the brief result of its physical properties. As a result, we have succeeded in synthesizing high-quality crystals of PrFe4Sb12 with higher Pr-filling factor and obtaining information about the crystalline electric field of PrFe4Sb12.
Filled skutterudites exhibit thermoelectric properties that comply with the concept of a "phonon-glass and electron-crystal (PGEC)". The optimal filled skutterudite for PGEC would have filler atoms that exhibit large thermal vibration amplitudes in the voids of the host skutterudite lattice. It is desirable that these loosely bound filler atoms give rise to strong phonon scattering without affecting the essential part of the band structure. In this report, the use of high-pressure technique for the synthesis of CoSb3-based filled skutterudites is reviewed. By using the high-pressure technique, new filled skutterudites, MxCo4Sb12 (M=Ge, Sn, and Pb), have been successfully synthesized without charge compensation of the host lattice. The structural aspect and the thermoelectric properties of MxCo4Sb12 are discussed.
In the present article, high-pressure and high-temperature synthesis of new skutterudite compounds using a Kawai-type cell was reported. The structure and usage of the Kawai-type cell were explained. The first filled skutterudite compounds containing Ge atoms in the host network have been prepared at 7 GPa and 800°C in the Ln-Rh-Sb-Ge system, where Ln = La, Ce, Pr, and Nd. Some characteristic features of the Skutterudite structure were discussed.
In this article, the experimental technique of synthesizing skutterudite compounds using multi-anvil-type high-pressure apparatus is described in detail. We also present the experimental technique of in situ observation for crystallization of the compounds under high temperatures and high pressures using synchrotron radiation. Using the technique for in situ X-ray diffraction, we determined the crystallization condition of some binary skutterudite compounds and filled skutterudite compounds under high pressure.
The attractive physical properties of filled skutterudites are reviewed in terms of strongly correlated electrons system. Furthermore, our recent results on the filled skutteduite phosphides synthesized under high-pressure and high-temperature conditions are reported. Sm-based filled skutterudites SmT4P12 (transition metal T = Fe, Ru, Os) show the variety of physical properties. We discuss the change of the characteristic behavior in SmT4P12 by the replacement of transition metal. We reveal that the heavy rare earth based filled skutteduite TbRu4P12 shows a multiple antiferromagnetic ordering. The anomalous phase diagram is discussed.
We found the first example of pressure-induced superconductivity in the filled skutterudite PrRu4P12 above 12 GPa, which shows a metal-insulator transition at 63 K and ambient pressure. In this article, we introduce our technical developments of measurements and results under high pressure using a diamond-anvil cell, such as electrical resistivity, powder X-ray diffraction and ac-calorimetry in the filled skutterudite.
We have developed a clamped piston-cylinder high pressure cell and performed ultrasonic measurements on the filled skutterudite compounds under hydrostatic pressures. Technical details and recent advances in the researches were reviewed by showing one of the compounds SmRu4P12 which exhibits a metal-insulator transition at TMI = 16.5 K and an additional transition at TN = 14 K. A pronounced elastic softening toward the additional temperature was induced in the application of pressure. Present results demonstrated that ultrasonic measurements on the filled skutterudite compounds under hydrostatic pressure are a powerful method to explore and elucidate a phase transition associated with a multipolar ordering.
We present here a setup for the dc magnetization measurements at high pressures and low temperatures using a Faraday-type capacitive magnetometer with a miniature BeCu piston-cylinder pressure cell, which allows us to pressurize sample up to 1.5 GPa at low temperatures. The magnetic force is measured capacitively by monitoring the displacement of parallel plate capacitor. The magnetometer can be used at temperatures down to 0.06 K and in high magnetic fields up to 15 T. The magnetometer with the pressure cell has a good sensitivity for magnetic moments of 10-4emu. Its application to the filled skutterudite superconductor PrOs4Sb12 is presented.
Liquids under negative pressures are in meta-stable and stretched states thermodynamically. So, the states transformed easily to coexisting states with vapors through heterogeneous nucleation processes. Therefore, it has been difficult even now to generate static negative pressures to measure liquids' properties under the pressures. In this paper, negative pressures were measured by the Berthelot method using a strain gauge pressure transducer. A sample liquid was acetone. Negative pressures increased with temperature cycles through two stages and attained a maximum value of ca.-20 MPa for acetone of ca.0.06 cm3.
We have developed two methods to determine the density of supercritical fluid sealed in a tube. One is the mass-volume method that is applicable to higher densities than 0.07 g cm-3 at 400°C when the fluid is water. In this method, the mass of the sample and the bore volume of the tube are determined precisely. The other is the chemical shift method, which takes advantage of the temperature dependence of the chemical shift and the PVT data. The latter is especially powerful at lower densities.
A hydrostatic pressure apparatus for the study of zooplankton throughout its life history from egg to adult was developed. The feature of this apparatus is as follows. (1) Pressure increases gradually. (2) A maximum of nine zooplanktons or their eggs can be observed independently at once. (3) This apparatus is small and easy to carry. The influence of pressure on the egg-hatching of Calanus sinicus was investigated using this system. The egg-hatching success decreased significantly with increasing pressure. Eggs would not survive if they did not hatch with the depth of water of 100 m or less.