Kazuyori Urabe

BaTiO3 Particle-Size Dependence of Ferroelectricity in BaTiO3/Polymer Composites

BaTiO3 particle-size dependence of ferroelectricity in BaTiO3/polymer composites was investigated from the viewpoints of the crystal phase in BaTiO3 powder and piezoelectric properties in BaTiO3/polymer composites. The crystal phase of BaTiO3 powder was transformed from tetragonal to pseudocubic at a critical particle size of 0.1 to 0.2 µm at room temperature. The piezoelectric charge constant (d33) and hydrostatic piezoelectric constant (dh) were obtained through poling treatment, although their values were small in BaTiO3/polymer composite using the pseudocubic BaTiO3 powder.

Characterization of Raney Ru: Effect of heat treatment

Raney Ru has been found to be an effective catalyst for ammonia synthesis, isotopic equilibration reaction (IER) of dinitrogen, and CO hydrogenation. For such reactions, preparation conditions are important because they may affect surface structure. The authors have studied Raney Ru by XPS, TEM, and other techniques under various conditions. A Raney catalyst has a higher concentration of an active element than a supported catalyst and is more easily studied by XPS. A super high voltage transmission electron microscope (SHV-TEM) enabled them to observe the lattice structures of microcrystals in the metallic block. Although several works have been reported on the surface characterization of Raney Ni or intermetallic catalysts, no such work has been reported on Raney Ru catalyst.

A New Method of Determining Short-Range Order Parameter in Relaxor Pb(Ni1/3Nb2/3)O3 by Magnetic Susceptibility Measurement.

We synthesized Pb(Ni1/3Nb2/3)O3 (PNN) and performed selected-area electron diffraction (SAD) in order to investigate the structure of the B-site array. In addition to the reflection from the basic cell, the SAD pattern of sintered PNN corresponds to the reciprocal plane normal to the [011] zone axis and showed diffuse scatterings at (½½½) positions. We also measured the magnetic susceptibility of PNN and discussed the short-range ordering around Ni2+ ions by analyzing the susceptibility based on a simple model.

Structure analysis of a new oxide Yb2TiMnO6

Abstract A new ternary oxide was synthesized from Yb 2 O 3, TiO 2 and MnO in an Ar atmosphere containing 1% H 2 at 1523K. The compound was characterized using a powder X-ray diffractometer (XRD), an electron probe microanalyzer (EPMA), and a transmission electron microscope (TEM). The oxide with the composition, Yb 1.8 Ti 1.3 Mn 0.7 O 6.0, had a hexagonal cell with lattice parameters a = 0.6137(1) nm and c = 1.1794(2) nm. The nonstoichiometric oxide was unstable following electron irradiation. The electron beam irradiation for 3–20 minutes changed the structure of the oxide. The selected area electron diffraction (SAD) patterns showed the changes, in which superlattice reflections vanished or new extra reflections appeared. The changed material had a domain structure composed of two types of structures, one structure had a basic cell with the a /3 dimension and the other one had a new structure with the 2 a /√3 dimension.

Reproducible Processing for High-Tc Superconducting Tl-Ba-Ca-Cu-O-Phases

In order to establish the reproducible processing for high-Tc superconducting Tl-Ba-Ca-Cu-O phases, three kinds of superconductive samples with different starting compositions of Tl:Ba:Ca:Cu=2:2:2:3, 2.5:2:2:3 and 3:2:2:3 were heat treated under various conditions. The optimum starting composition was found to be 2:2:2:3. A particular heat treatment of the 2:2:2:3 sample elicited polycrystalline materials showing a zero-resistance temperature at 120.3 K and an onset temperature of the diamagnetic shift at 127 K.

Magnetic properties of Eu2MnxZr2−xO7−δ

Abstract Compounds formed in the ternary system, MnO–Eu 2 O 3 –ZrO 2 , have been prepared from starting mixtures with a formula, Eu 2 Mn x Zr (2− x ) O 7− δ , by firing at 1623 K in a reducing atmosphere. Those compounds are solid solutions of a pyrochlore type and a rare earth type. The former occurs in the region of x being less than 0.65 and the latter appears in the region x being larger than 0.7. Solubility of manganese ions in those solid solutions has been measured by EPMA and the maximum value reaches about 1.8%. Magnetic properties of the solid solutions indicate that little amount of manganese ions is incorporated in the solid solutions.

Electron microscopic study of a newly formed Eu2MnZrO7 − δ with a fluorite-related type structure

A ternary compound, Eu{sub 2}MnZrO{sub 7{minus}{delta}} was synthesized in a reducing atmosphere at 1,623 K. The compound has the basic cell of the fluorite type. Electron diffraction patterns consisted of the diffuse reflections in addition to the fundamental reflections. In the dark-field image, the existence of microdomains with different orientations was observed. Each domain has a modulation along the [111] of the basic cell with a sequence of the 1/2(111). It is suggested that the divalent manganese ions, Mn{sup 2+}, were formed in the reducing atmosphere, which resulted in the formation of the fluorite-type compound.

Thermal Conductivity of BeO-Doped SiC Ceramic at 5 to 1000 K

Thermal conductivity of a BeO-added SiC ceramic was measured using steady-state longitudinal heat flow and laser flash techniques. A significant change of the thermal conductivities between the ceramic and high-purity, single-crystal was not observed above 300 K, however was found below this temperature. Low conductivity of the ceramic at temperatures below 40 K is due to the presence of grain boundaries, since the conductivity decreased according to Klemens’s T 3 law, and the calculated phonon mean free path reaches the magnitude of the grain size.

Electron microscopy study of a manganese-doped holmium zirconium oxide solid solution

Abstract A new material, manganese-doped holmium zirconium oxide solid solution, was synthesized in a reducing atmosphere at 1623 K. Microstructural characterization of the material was performed using transmission electron microscopy (TEM) in conjunction with energy-dispersive X-ray spectroscopy (EDXS). It was confirmed that the material consisted of two phases having a similar basic cell related to the fluorite-type structure. One of the phases builds up the matrix and reveals the fluorite-type structure. The other phase has a structural modulation along the direction of the basic cell, with spacing two times that of the (110) plane, and occurs as small precipitates, 70–100 nm in size, embedded in the matrix. A lattice correspondence was maintained between the precipitates and the matrix with a small strain. The holmium content in the precipitates is higher than that of the matrix, which gives rise to the structure modulation along the direction.

Hot-Forge-Sintering of Fine Alumina Powder.

Fine alumina powder prepared by an ammonium alum method was encapsulated in a stainless steel mold with the dimensions of O.D. 22φ∼I.D. 10φ×30hmm. The mold containing alumina was preheated at 1200 or 1300°C for about 8 minutes, and then immediately press-forged under uniaxial compressive load. The particle size of the starting powder (0.15μm) grew to about 0.2 or 0.3μm during the preheating, and a modarately dense polycrystal with the grain size of 0.2 or 0.3μm was obtained by the masstransport mechanism promoted during the deformation. The hot-forged polycrystalline alumina, however, did not show satisfactory hardness, because of some stored residual stress around the grain boundary. A polycrystalline alumina with excellent hardness was obtained after annealing the hot-forged body at a relatively law temperature of 1000 to 1100°C for 24 hours. The densification mechanisms of alumina powder during the hot-forging and annealing processes were investigated through microstructural observations by TEM and SEM.