Preparation of nm-sized BaO3 particles using a new 2-step thermal decomposition of barium titanyl oxalate

To obtain inpurity-free and nm-sized barium titanate (BaTiO₃) particles, a new 2-step thermal decomposition method from barium titanyl oxalates (BaTiO(C₂O₄)₂ · 4H₂O) was proposed. At the 1st step, BaTiO(C₂O₄)₂ · 4H₂O was annealed at 400°C for 1 h in the O₂ flow. The annealing temperature of 400°C was chosen for the following reasons; (1) no formation of BaCO₃ and TiO₂ and (2) the complete removal of H₂O and other carbon species. This compound obtained at 400°C was amorphous phase, and its chemical composition was BaCO₃-TiO₂. When this compound was annealed in air at higher temperatures, the large BaTiO₃ particles were prepared with by-products such as BaCO₃. Thus, at the 2nd step, to prevent the crystal growth and the formation of BaCO₃, this compound was annealed above 600°C in vacuum. Finally, the BaTiO₃ single crystals with a size with 16.5 nm were prepared around 620°C. These BaTiO₃ fine particles were characterized using various methods to investigate defects and impurities in the particles. As a result, it was confirmed that there was no impurity in the BaTiO₃ lattices.     

Influence of CuO on the Structure and Piezoelectric Properties of the Alkaline Niobate-Based Lead-Free Ceramics

Recently, it was reported that the alkaline niobate-based (K,Na,Li)(Nb,Ta,Sb)O₃ (LF4) perovskite ceramics showed excellent piezoelectric properties and have been regarded as a new candidate of lead-free piezoelectric materials. However, the effects of additives on the piezoelectric property of LF4 have not been studied intensively so far. In this study, the effect of CuO addition to the LF4 was investigated. The sample showed a tetragonal phase at room temperature and also a second phase with low melt point. With 0.05 wt% CuO added, the Cu²⁺ firstly incorporated into the A site, while higher amounts of Cu²⁺ substituted B-site ions. The CuO-doping changed the LF4 to "hard" piezoelectric ceramics with improvement of mechanical quality factor from 26 to 137 but the piezoelectric d ₃₁ constant and the electromechanical coupling constant reduced drastically at the same time.     

Evaluation and Statistical Analysis of Dielectric Permittivity of BaTiO3 Powders

A slurry method was used to determine the dielectric permittivity (ɛ_r) of BaTiO₃ powders with different characteristics, such as tetragonality ( c / a ratio), density, particle size, and specific surface area. The ɛ_r of powders highly depended on their characteristics. In order to extract the effect of each characteristic, a statistical analysis was carried out to represent the ɛ_r of powders with an empirical formula. A fairly good agreement was obtained between observed data and those estimated from the formula. The ɛ_r decreased with particle size because of the size effect of BaTiO₃ and high tetragonality and density was essential to obtain high ɛ_r of powders.     

Novel polymer-ceramic nanocomposite based on new concepts for embedded capacitor application (I)

A rapid growth of mixed-signal integrated circuits is driving the needs of multifunction and miniaturization of the component in electronics applications. Polymer-ceramic composites have been of great interest as embedded capacitor materials because they enabled companies to combine the processability of polymers with the high dielectric constant of ceramics. This paper presents the preparations and performance characterizations of novel polymer-ceramic nanocomposites based on new concepts for embedded capacitor application. First, metal particle nickel-filled nanocomposite with high dielectric constant was evaluated as a candidate for embedded capacitors. Two types of nickel particles were selected with the size of 400 and 150nm, respectively. With proper filler loading and highly dispersed, a high dielectric constant of over 90 was observed with a filler loading ratio of 60-vol%. Second, the surface modification of a barium titanate (BTO) particle was also attempted in nanocomposite. Phthalocyanine-coated BTO (Pc-coated BTO) was selected as filler to prepare the composite. Its dielectric constant was observed as over 80 at 1MHz, which was much higher than that of composite derived from commercial BTO. Last, in order to improve the processability of the nanocomposite, 4, 4'-diphenylmethane bismaleimide (BMI) was selected as a matrix polymer by the combination with polyamide (PA). Higher dielectric constant nanocomposite derived from PA/BMI and Pc-coat BTO was obtained, and its potential application towards embedded capacitors was also evaluated.     

Effects of interface structures on cracking in AlN(11\overline 2 0)/α-Al2O3 (1\overline 1 02) epitaxial films

The crystal structures and microstructures of AlN $(11\overline 2 0)$ /GaN $(11\overline 2 0)$ epitaxial films on just-cut and ±4° off-cut Al₂O₃ $(1\overline 1 02)$ substrates grown by metal organic chemical vapor deposition (MOCVD) are investigated using high-resolution X-ray diffractometry and transmission electron microscopy, and are compared with those of AlN $(11\overline 2 0)$ film on +4° off-cut Al₂O₃ $(1\overline 1 02)$ substrate. In the AlN/Al₂O₃(+4° off-cut) film and the AlN/GaN/Al₂O₃ (just-cut, ?4° off-cut) films, cracks parallel to the $[1\overline 1 00]$ _AlN direction and perpendicular to the interfaces of the films and the substrates are observed. The AlN/Al₂O₃ and AlN/GaN interfaces exhibit low crystallinity in which moiré fringes are observed. On the other hand, in the AlN/GaN/Al₂O₃(+4° off-cut) film, no cracks form. The GaN layer buffers the lattice mismatch between the AlN film and the Al₂O₃ substrate, and moiré fringes are not observed in the GaN/Al₂O₃ and AlN/GaN interfaces. On the basis of these results, the effects of the interface structures on cracking are discussed.     

Increased tumor localization by monoclonal antibody A7 after F(ab')2 fragmentation in athymic nude mice bearing human pancreatic carcinomas

Much recent research has been directed toward the use of monoclonal antibodies (MoAbs) for the immunodetection of solid tumors. In pancreatic cancer, conventional immunoscintigraphy using intact MoAbs remains disappointing. In this study, 125I-labeled F(ab')2 fragments produced by pepsin digestion of MoAb A7 were injected intravenously into nude mice bearing human pancreatic cancer, HPC-YS, xenografts that have previously been shown to react specifically with MoAb A7. The tumor tissue/blood ratio of 125I-labeled F(ab')2 fragments of MoAb A7 increased with time and was much higher than those for normal tissues. Moreover, the tumor tissue/blood ratio of 125I-labeled F(ab')2 fragments was greater than that of intact MoAb A7, although the F(ab')2 accumulation was less than that of intact MoAb A7 in the tumor. These results suggest that F(ab')2 fragments of MoAb A7 may be suitable carriers of radionuclides for immunodetection of human pancreatic cancer.     

Cytarabine-induced pericarditis

We report two cases of cytarabine (Ara-C) induced pericarditis. The first patient was a 61-year-old man with de novo acute myelogenous leukemia (AML) with trilineage myelodysplasia (M2). Fever and pericardial effusion developed after treatment with low-dose Ara-C and etoposide (VP16) during the patient's second leukemic relapse. The second patient was a 65-year-old man with myelodysplastic syndrome (MDS) transformed into AML (M2). He achieved a complete remission after treatment with low-dose Ara-C and VP16. However, during consolidation chemotherapy consisting of oral cytarabine ocfosfate and VP16, fever and pericardial effusion developed. In both cases, pericardiocentesis revealed exudative effusion with many neutrophils. Neither bacterial nor fungal infection was demonstrated. Chest symptoms and fever were resolved by methylprednisolone pulse therapy and pericardial drainage. Both patients were given a diagnosis of pericarditis caused by allergic reaction to Ara-C. We also report on 6 other patients with Ara-C syndrome who have been encountered by our hospital.     

Preparation of barium titanate nanoparticle sphere arrays and their dielectric properties

Barium titanate (BaTiO3) nanoparticles from 27 to 192 nm were prepared by the 2-step thermal decomposition method from barium titanyl oxalate nanoparticles. These particles were dispersed well into 1-propanol, and dense BaTiO3 nanoparticle sphere arrays without stress-field were prepared by the meniscus method. Temperature dependence of dielectric properties was successfully measured using these dense nanoparticle sphere arrays, and size effect on dielectric properties was discussed.