Nano-sized BaTiO 3 powders with narrow size distribution and high tetragonality were attempted to be synthesized by the rotary-hydrothermal process in a water system as a novel technique, using a mixture of anatase-type TiO 2 and Ba(OH) 2 as starting material. The rotary-hydrothermal syntheses were performed under conditions with a rotary-speed of 20 revolutions per minute at 423-523 K for 3-96 h. Highly-and monodispersed BaTiO 3 powders mainly composed of coarse-faceted particles with the tetragonal phase were successfully synthesized by controlling the conditions for rotary-hydrothermal treatments. TEM and TG results revealed that these coarse-faceted BaTiO 3 particles contained very few structural defects such as hydroxyl content. Thus, the rotary-hydrothermal process was a useful method to synthesize very high-quality BaTiO 3 particles, and the further control of various conditions of the rotaryhydrothermal treatment is expected to control the crystalline phase and microstructures of final BaTiO 3 powders.

This study describes the nonlinear characteristics of SrCoO 3 -doped ZnO varistors and multilayer ceramic varistors (MLCVs) with copper electrodes, both of which are sintered in a reducing atmosphere. Due to postannealing effects in air or N 2 with low-oxygen concentration (0.02%), bulk disks can be sintered in a reducing atmosphere, with a usable V 1 mA /mm (e.g., 1600 V for bulk bodies or 1200 V for Cu cofiring) and highly nonlinear indices (a 10 lA 5 V 1 mA /V 10 lA , 1.3), regardless of whether cofiring with Cu electrodes on disk surfaces was conducted or not. On the basis of this procedure, Cu-MLCVs were successfully produced, without oxidation of Cu-internal electrodes or structural defects. They exhibited high stability as well as a useful nonlinearity of V 1 mA 5 10.4 V and a 10 lA 5 1.93. The resultant stability against electrostatic discharge (ESD) satisfies the highest standard of level 4 in IEC61000-4-2 (ESD stability test). This is the first report to show that MLCVs with base metals have practical properties, including stability.

Highly lattice mismatched (HM 2 ) heteroepitaxial growth of cubic zincblende c-AlN and c-GaN on Si (001) was performed by MBE using plasma excited nitrogen sources without using a low temperature buffer layer. The early stage of the direct nucleation of AlN and GaN on a Si substrate using microwave and radio frequency plasma-assisted MBE was studied. The islands of a zincblende structured material (c-SiN x [a = 0.43 nm]), effectively worked as a seed for successive coherent growth of c-AlN and c-GaN oriented 〈001〉. The growth of c-AlN and c-GaN was analyzed by reflection high energy electron diffraction, X-ray diffraction, and photoluminescence.1 Introduction Hybrid application of group III nitride semiconductors with silicon technology is a promising one for optical and electronic applications. The growth method of molecular beam epitaxy (MBE) is the most suitable one for interface flatness control and composition control of alloy crystals for optical and electronic applications. Although the hexagonal wurzite (W) phase (h-) of AlN and GaN is currently used for various applications, the cubic zincblende (ZB) (c-) phase is more attractive, because of the doping property and the similarity of the cubic system of Si technology for hybrid application. The growth of ZB group III nitrides by MBE was reported by using a low temperature buffer layer or surface pre-treatments of carbonization or nitridation for a Si substrate [1][2][3][4][5][6][7][8][9][10][11][12] and for other substrates [13 -20]. To overcome the problem of highly lattice mismatched (HM 2 ) hetero-epitaxial growth [21] is important for hybrid application. No direct growth of GaN from single crystal islands of silicon nitride (SiN x ) on Si(001) was reported before, except for the formation of amorphous SiN x at the GaN/Si interface [6][7][8]. The amorphous SiN x substrate operated as nucleation cores of h-GaN [7]. Single crystal islands work as coherent multi nuclei for the direct growth, which has merits to reduce the interface electric resistance for vertical devices and to reduce the process steps of device preparation. In this report the heteroepitaxial growth of ZB c-AlN and c-GaN on Si (001) will be performed by MBE without a low temperature buffer layer using nitrogen plasmas of microwave (µ-) and radiofrequency (rf-) discharges. Coherent growth for the single phase of cubic nitrides depending on plasma sources will be discussed.

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The grain-boundary and its electrical characteristics in SrCoO3doped ZnO varistors were studied. The grain-boundary around ZnO-grain is probably composed of SrCoO3, and its electrical behavior is clearly different from two conventional types of Bi-and Pr-based ZnO varitors. The non-linearity and characteristic behavior could be explained by considering the n-p-n hetero-structure at the grain boundary. SrCoO3 in the grain-boundary region should play crucial roles of not only the appearance of non-liner property but also the formation of different hetero-structure from double Schottky-barrier model on conventional varistors.