Susumu Imashuku

Improvement of Grain-Boundary Conductivity of Trivalent Cation-Doped Barium Zirconate Sintered at 1600°C by Co-doping Scandium and Yttrium

Scandium and yttrium co-doped barium zirconate [BaZr 0.85 Sc x Y 0.15-x O 3-δ (x = 0, 0.05, 0.075, 0.10, 0.15)] have been investigated in terms of phase relationship, microstructures, and electrical conductivity. The bulk conductivity of the scandium and yttrium co-doped barium zirconate increased with the dopant ratio of yttria. BaZr 0.855 Sc 0.05 Y 0.10 O 3-δ had the highest grain-boundary conductivity among the scandium and yttrium co-doped barium zirconates in this study. But, BaZr 0.85 Sc 0.15 O 3-δ BaZr 0.85 Sc 0.10 Y 0.05 Ο 3-δ , BaZr 0.85 S 0.75 Y 0.075 O 3-δ , and BaZr 0.85 Sc 0.05 Y 0.10 Ο 3-δ consisted of a single cubic perovskite phase at 1600°C and their densities of grain-boundary were smaller than that of BaZr 0.85 Y 0.15 Ο 3-δ . From the observation of microstructure and results of grain boundary-conductivity measurement, we can say that yttrium is a dopant that increases specific grain-boundary conductivity and bulk conductivity, and scandium is a dopant that increases the grain size. Thus, there is a trade-off relation between the grain size and specific grain-boundary conductivity based on the mixing ratio of scandia to yttria. The total conductivity of BaZr 0.85 Sc 0.05 Y 0.10 O 3-δ at 600°C was estimated to be 1.6 X 10 -2 S cm -1 , which is the highest-class conductivity among reported trivalent cation-doped barium zirconates.

Sintering properties of trivalent cation-doped barium zirconate at 1600°C

Typical microstructures of BaZr 0.85 Y 0.15 O 3-δ sintered for 4-24 h at 1600°C were mixtures of larger and smaller grains. Well-grown and homogeneous grains of BaZr 0.85 Y 0.15 O 3-δ were observed by adding an extra amount of barium oxide from stoichiometric composition or extending the sintering time to 100 h. Such an extra amount of barium oxide is expected to decrease chemical stability in a wet atmosphere, and we observed the precipitation of yttria after 100 h sintering. However, we did not meet such difficulties in sintering BaZr 0.85 Sc 0.15 O 3-δ . Large and uniform grains were observed in BaZr 0.85 Sc 0.15 O 3-δ by sintering for 24 h.

Water content and related physical properties of aliphatic quaternary ammonium imide-type ionic liquid containing metal ions

Abstract The ionic liquid, trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA–Tf2N), has a wide electrochemical window of more than 5 V and is considered to be hydrophobic because of two –CF3 groups in its Tf2N anion. However, a small amount of water remains in the ionic liquid even after dehydration in vacuo, which causes some problems in metal electrodeposition when using the ionic liquid as a solvent. We measured the water content of the ionic liquids, TMHA–Tf2N containing M(Tf2N)n (M ¼ H, Li, Mg, Ni, Cu, Zn, La, and Dy; n ¼ 1, 2, or 3), as well as their kinematic viscosity and electrical conductivity in the temperature range of 25–130 1C. Furthermore, differential scanning calorimetry was performed for these ionic liquids to find their glass transition temperature, crystallization temperature, and melting temperature. The water content of TMHA–Tf2N containing M(Tf2N)n salts decreased with an increase in temperature. At the same time, the kinematic viscosity decreased and the electrical conductivity increased. By measuring the optical absorption spectrum, it was found that the metal ions in TMHA–Tf2N were hydrated. The addition of M(Tf2N)n to TMHA–Tf2N, increased the water content at a constant temperature, which resulted in slight increases in the kinematic viscosity and decrease in the electrical conductivity. A Walden-like plot of the electrical conductivities against the kinematic viscosities, measured over various temperatures and water contents, gave a single straight line.

Development of miniaturized electron probe X-ray microanalyzer.

A miniaturized electron probe X-ray microanalyzer (EPMA) with a small chamber including the electron source and the sample stage was realized using a pyroelectric crystal as an electron source. The EPMA we propose is the smallest reported so far. Performance of the EPMA was evaluated by investigating energy of obtained continuous X-rays and lower detection limits of transition metals (titanium, iron, and nickel). End point energy (Duane-Hunt limit) of continuous X-rays of 45 keV was obtained. However, it is expected that the EPMA can analyze characteristic X-rays with energy less than 20 keV. The EPMA was able to measure titanium, iron, and nickel wires whose projected areas were more than 0.03 mm(2).

Note: Portable rare-earth element analyzer using pyroelectric crystal

We report a portable rare-earth element analyzer with a palm-top size chamber including the electron source of a pyroelectric crystal and the sample stage utilizing cathodoluminescence (CL) phenomenon. The portable rare-earth element analyzer utilizing CL phenomenon is the smallest reported so far. The portable rare-earth element analyzer detected the rare-earth elements Dy, Tb, Er, and Sm of ppm order in zircon, which were not detected by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. We also performed an elemental mapping of rare-earth elements by capturing a CL image using CCD camera.

Focused electron beam in pyroelectric electron probe microanalyzer

We report a method to focus the electron beam generated using a pyroelectric crystal. An electron beam with a spot size of 100 μm was achieved by applying an electrical field to an electroconductive needle tip set on a pyroelectric crystal. When the focused electron beam bombarded a sample, characteristic X-rays of the sample were only detected due to the production of an electric field between the needle tip and the sample.

Note: Development of target changeable palm-top pyroelectric x-ray tube.

A target changeable palm-top size x-ray tube was realized using pyroelectric crystal and detachable vacuum flanges. The target metals can be exchanged easily by attaching them on the brass stage with carbon tape. When silver and titanium palates (area: 10 mm(2)) were used as targets, silver Lα and titanium K lines were clearly observed by bombarding electrons on the targets for 90 s. The intensities were the same or higher than those of previously reported pyroelectric x-ray tubes. Chromium, iron, nickel, copper, and zinc K lines in the x-ray tube (stainless steel and brass) disappeared by replacing the brass stage and the stainless steel vacuum flange with a carbon stage and a glass tube, respectively.

Possibility of scanning electron microscope observation and energy dispersive X-ray analysis in microscale region of insulating samples using diluted ionic liquid.

The possibility of scanning electron microscope (SEM) observation and energy dispersive X-ray (EDX) spectrometry analysis in microscale regions of insulating samples using diluted ionic liquid was investigated. It is possible to obtain clear secondary electron images of insulating samples such as a rock and mineral at 5,000 times magnification by dropping 10 μL of 1 wt% of 1-ethyl-3-methylimidazolium acetate (EMI-CH₃COO) diluted with ethanol onto the samples. We also obtained EDX spectra of the samples in microscale regions (~5 μm²) without overlapping EDX spectra of other minerals with different composition. It might be possible to perform quantitative analysis of the samples if a method that does not need standard samples is applied or an X-ray detector sensitive for light elements was attached. The method of dropping 1 wt% EMI-CH₃COO diluted with ethanol onto insulating samples is useful for SEM observation, EDX analysis in microscale regions, and the preservation of scarce rock and mineral samples because ionic liquid can be easily removed with acetone.

X-Ray Excited Optical Luminescence and Portable Electron Probe Microanalyzer–Cathodoluminescence (EPMA–CL) Analyzers for On-Line and On-Site Analysis of Nonmetallic Inclusions in Steel

The potential of the application of an X-ray excited optical luminescence (XEOL) analyzer and portable analyzers, composed of a cathodoluminescence (CL) spectrometer and electron probe microanalyzer (EPMA), to the on-line and on-site analysis of nonmetallic inclusions in steel is investigated as the first step leading to their practical use. MgAl2O4 spinel and Al2O3 particles were identified by capturing the luminescence as a result of irradiating X-rays in air on a model sample containing MgAl2O4 spinel and Al2O3 particles in the size range from 20 to 50 μm. We were able to identify the MgAl2O4 spinel and Al2O3 particles in the same sample using the portable CL spectrometer. In both cases, not all of the particles in the sample were identified because the luminescence intensities of the smaller Al2O3 in particular were too low to detect. These problems could be solved by using an X-ray tube with a higher power and increasing the beam current of the portable CL spectrometer. The portable EPMA distinguished between the MgAl2O4 spinel and Al2O3 particles whose luminescent colors were detected using the portable CL spectrometer. Therefore, XEOL analysis has potential for the on-line analysis of nonmetallic inclusions in steel if we have information on the luminescence colors of the nonmetallic inclusions. In addition, a portable EPMA-CL analyzer would be able to perform on-site analysis of nonmetallic inclusions in steel.

Scanning Electron Microscope-Cathodoluminescence Analysis of Rare-Earth Elements in Magnets.

Scanning electron microscope-cathodoluminescence (SEM-CL) analysis was performed for neodymium-iron-boron (NdFeB) and samarium-cobalt (Sm-Co) magnets to analyze the rare-earth elements present in the magnets. We examined the advantages of SEM-CL analysis over conventional analytical methods such as SEM-energy-dispersive X-ray (EDX) spectroscopy and SEM-wavelength-dispersive X-ray (WDX) spectroscopy for elemental analysis of rare-earth elements in NdFeB magnets. Luminescence spectra of chloride compounds of elements in the magnets were measured by the SEM-CL method. Chloride compounds were obtained by the dropwise addition of hydrochloric acid on the magnets followed by drying in vacuum. Neodymium, praseodymium, terbium, and dysprosium were separately detected in the NdFeB magnets, and samarium was detected in the Sm-Co magnet by the SEM-CL method. In contrast, it was difficult to distinguish terbium and dysprosium in the NdFeB magnet with a dysprosium concentration of 1.05 wt% by conventional SEM-EDX analysis. Terbium with a concentration of 0.02 wt% in an NdFeB magnet was detected by SEM-CL analysis, but not by conventional SEM-WDX analysis. SEM-CL analysis is advantageous over conventional SEM-EDX and SEM-WDX analyses for detecting trace rare-earth elements in NdFeB magnets, particularly dysprosium and terbium.