Fumihito Shikanai

Pure lead nanoparticles with stable metallic surfaces, on perovskite lead strontium titanate particles

We demonstrate an efficient method of fabrication for pure lead nanoparticles with non-oxidized surfaces, supported on perovskite lead strontium titanate particles with a size distribution from tens to several hundreds of nanometers. The fabrication method is based on co-precipitation and subsequent annealing in air at 600 degrees C. Transmission electron microscopy revealed that the pure lead nanoparticles show structural fluctuations under intense electron-beam irradiation, like gold and platinum nanoparticles.

A gradational system for ferroelectric nanosized (Pb0.7Sr0.3)TiO3 particles

Synchrotron radiation x-ray diffraction measurement was performed to investigate the size effect in ferroelectric nanosized (Pb(0.7)Sr(0.3))TiO(3) particles with various sizes ranging from 10 to 200 nm. The 200 and 002 Bragg reflections were separated using low energy synchrotron radiation x-rays. The peak profiles of the 002 reflections show a large broadening and asymmetry for all particle sizes compared with those of the 200 reflections. These anomalously wide and asymmetric peak profiles become marked for peaks with a large l. The aspect ratio of the lattice constants c/a and the atomic distance between the anions and cations decrease gradually in the vicinity of the surface of the particles, indicating that the asymmetrical profiles can be attributed to the formation of a gradational system.

Influence of Deviatoric Strain for Superconducting Parameters of

The tensile strain dependence of the upper critical field B_c2 for Nb₃Sn wires was measured using a new apparatus for applying tension at low temperature. The critical current I_c calculated from the strain-dependent B_c2 measurements is the almost consistent with the measured I_c. In the measurements by a new apparatus, the axial and the lateral applied strains were examined by the strain gauges attached onto the wire. The deviatoric strain epsiv_dev and the hydrostatic strain epsiv_hyd were estimated by the axial and the lateral strain. We found the deviatoric strain dependence of B_c2 is different between the tensile and compressive strain states. This means that the hydrostatic strain also should be taken into account in order to understand the strain effects on the superconducting properties of Nb₃Sn.

\hbox{Nb}_{3}\hbox{Sn}

ABSTRACT Bi4 − x La x Ti3O12 (BLT) nano-particles have been synthesised by the chemical co-precipitation method utilizing a polymeric precursor. The particle size decreases from 100 to 40 nm with the increase of La content (x = 0 ∼ 1) owing to the increase of a reaction temperature. The axial ratio a/b of BLT decreases with the increase of La content reflects a relaxation of structural distortion from its ideal tetragonal structure. A monoclinic to orthorhombic transition occurs at La > 0.75. The existence of the soft mode in Raman spectra above x = 0.75 demonstrates a displacive nature of orthorhombic to tetragonal phase transition. No noticeable size effect on physical properties is observed.

Wires

Crystal structures of protonic conductor K 3 H(SeO 4 ) 2 in the phase I (conducting phase) and phase II (room-temperature phase) have been determined using a time-of-flight (TOF) neutron diffractometer VEGA. SeO 4 tetrahedra in the phase I were rotationally displaced with the occupancy 1/3 and the crystal structure in the phase II was remain locally. Proton distribution maps were obtained from the maximum entropy method (MEM) describe that the amount of the proton in a hydrogen bond were decline from 87.3% to 21.4% with increasing the temperature and 13.4% of protons exist at inter-layer space. Incoherent quasi-elastic neutron scattering (QENS) experiments performed by LAM80-ET spectrometer yield the QENS spectra of conducting protons. Proton diffusion constants are estimated as 1.9(1) × 10 − 10 m 2 /s at 393 K and 2.1(3) × 10 − 10 m 2 /s at 413 K, respectively.

PHYSICAL PROPERTIES OF FERROELECTRIC BI4–xLAxTI3O12 NANO-PARTICLES SYNTHESIZED BY THE CHEMICAL CO-PRECIPITATION METHOD

ABSTRACT A single crystal of β-terbium molybdate, β-Tb2(MoO4)3 (TMO), was grown using the floating zone (FZ) method. The single crystal is transparent and light green. To evaluate the single crystal, it was subjected to powder X-ray diffraction measurements. Rietveld refinement was performed for the diffraction pattern. In addition, studies of its heat capacity were performed. The first-order ferroelectric and ferroelastic phase transition temperature, TC, was found to be 431.98 K. The results show that the grown crystal is the single-phase, high quality TMO.

Neutron Powder Diffraction Study of Protonic Conductor K3H(SeO4)2

Dynamical properties of protonic conductor K3H(SeO4)2 were examined by using various techniques, Brillouin scattering, quasi elastic, and inelastic neutron scattering. No significant anomaly was observed in longitudinal and transverse acoustic modes. In each experiment, a Lorentzian shaped spectrum was observed at extremely low energy, (less than 0.1 meV). The spectra in Brillouin and inelastic neutron scattering at the zone boundary originate from rotational modes of SeO4 tetrahedra at Г- and L-point, respectively. The peak positions, shapes, and widths of the spectra are consistent with each other, while the integrated intensities show complementary temperature dependence. The lifetimes of those modes, about 10−10 s, agree with the stationary time of conduction protons obtained from Q dependence of width in quasi elastic neutron scattering.