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The physical origin of the residual stresses developed in the ceramic layer of the active region in a multilayer ceramic capacitor was numerically investigated. The compressive in-plane stress components σ11 and σ22 originate without regard to the presence of the margins but rather from the difference in in-plane thermal shrinkage between ceramic and metal electrode. The out-of-plane stress component σ33 physically originates mainly through the presence of the housing margin; the presence of the lateral margin is a minor source: the more ceramic-rich margins hinder the apparent vertical shrinkage of the active region to yield tensile σ33. © 2007 American Institute of Physics.

While Pb (Zn13 Nb23) O3 -PbTi O3 (PZN-PT) single crystals have shown superior ferroelectric properties, less scientific and technical interests have been placed on PZN-PT polycrystalline ceramics due to their poor thermodynamic stability and the difficult processing conditions. Here, we stabilized the PZN-PT based ceramics by adding alkali niobates such as NaNb O3 (NN) and KNb O3 (KN) and investigated their structure and dielectric properties. Two stabilization mechanisms are suggested in alkali niobate added PZN-PT ceramics, increased tolerance factor and enhanced electronegativity difference. KN stabilized the perovskite structure of PZN-PT based ceramics more effectively than NN. Both PZN-PT-KN and PZN-PT-NN ceramics showed the typical behavior of relaxor ferroelectrics. The temperature of maximum dielectric constant of PZN-PT-NN was slightly higher than that of the PZN-PT-KN, which was explained by the difference in ionic size and B -site ordering. © 2007 American Institute of Physics.

We investigate the ferroelectric properties of Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3(PZN-PT)-based ceramics, which are stabilized by adding a small amount of NaNbO 3 (NN) and KNbO 3 (KN). As the content of alkali niobate increased, the ferroelectric properties of Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3-RNbO 3 (PZN-PT-RN; R=Na, K) became softer, which was more pronounced in PZN-PT-KN. The difference in the piezoelectric properties between PZN-PT-KN and PZN-PT-NN was explained by the cation size effect. Because the ionic size of Na is smaller than that of K, the Na ion can retain the ferroelectricity of the solid solution more effectively. The field-induced strain of 85PZN-5PT-10NN under 10 kV/cm was as high as 0.1%. Also, the addition of NN increased the tunability of dielectric constant significantly. At a composition of 85PZN-5PT-20NN, the tunability was 90% and no hysteresis was observed. In contrast to RN, the increase in the content of PT caused the transition from relaxor to normal ferroelectrics, which were accompanied by the structural change from the rhombohedral to tetragonal phase. © 2007 The American Ceramic Society.

Nanosized particles of SnSb alloy were coated on the surface of multiwalled carbon nanotubes (CNTs) by reductive precipitation of metal chloride salts within a CNT suspension. The SnSb-CNT nanocomposite snowed a high reversible capacity of 480 mAh g-1 and stable cyclic retention until the 50th cycle. The improvement of reversible capacity and cyclic performance of the SnSb-CNT composite is attributed to the nanoscale dimension of the SnSb alloy particles (<50 nm) and the structural advantages of CNTs as a framework material. The CNTs could be pinning the SnSb alloy particles on their surfaces so as to hinder the agglomeration of SnSb particles, while maintaining electronic conduction as well as accommodating drastic volume variation during electrochemical reactions. © 2007_American Chemical Society.

The influence of margin widths on the evolution of residual stress components in a multilayer ceramic capacitor has been investigated numerically by systematically varying the widths of the housing and lateral margins. As for the in-plane residual stress components (compressive), σ11 is much relieved by the housing margin which exists along the length (axis 1) direction, while σ22 is much relieved by the lateral margin which exists along the width (axis 2) direction. The out-of-plane stress component σ33 (tensile) increases via both the housing and lateral margins within the range of the critical width (about 150 μm), beyond which σ33 is not markedly influenced by the widths of margins. © 2006 Elsevier B.V. All rights reserved.

Hygroscopic Mg(OH) 2 gel was topotactically decomposed on TiO 2 particle surfaces, resulting in highly nanoporous MgO-coated TiO 2 particles. The highly hygroscopic and nanoporous MgO shell absorbed more water molecules and hydroxyl groups from the environment to yield an improved photocatalytic property of the core-shell particles as compared to the uncoated TiO 2 counterpart. © 2006 American Institute of Physics.

This paper presents the results of a transient dynamic analyses and experiments on an ultrasonic linear motor (USLM). For a simulation of dynamics of the ultrasonic linear motor, an analytic method has been used. Numerical analysis was performed to determine the precise characteristics of the ultrasonic linear motor. The contact between slider and stator has hindered the transient dynamic finite element method (FEM) analysis of ultrasonic motors. In this study, the problem was solved using the reaction force. Transforming the applied electric field to the mechanical reaction force, transient dynamic analysis was performed in contact condition. The resonance frequency and the velocity of the linear motor were determined to be 35.6 kHz and 34 cm/s respectively from FEM analysis. And the equilibration time when the vibration and velocity of motor reach the steady states can be calculated. The validity of analysis results including eigen frequencies and a velocity of a motor, was confirmed by comparison with steady state analysis and experiments. ©2005 The Japan Society of Applied Physics.

Using neutron pair distribution function analysis over the temperature range from 1000 to 15 K, we demonstrate the existence of local polarization and the formation of medium-range, polar nanoregions (PNRs) with local rhombohedral order in a prototypical relaxor ferroelectric Pb(Mg1/3Nb 2/3)O3. We estimate the volume fraction of the PNRs as a function of temperature and show that this fraction steadily increases from 0% to a maximum of ∼30% as the temperature decreases from 650 to 15 K. Below T ∼ 200 K the volume fraction of the PNRs becomes significant, and PNRs freeze into the spin-glass-like state. © 2005 The American Physical Society.

Sol-gel-derived Mg(OH) 2 gel was coated onto TiO 2 nanoparticles, and the subsequent thermal topotactic decomposition of the gel formed a highly nanoporous MgO crystalline coating. The specific surface area of the electrode that was prepared from the core-shell-structured TiO 2 nanoparticles significantly increased compared with that of the uncoated TiO 2 electrode. The increase in the specific surface area of the MgO-coated TiO 2 electrode was attributed to the highly nanoporous MgO coating layer that resulted from the topotactic reaction. Dye adsorption behavior and solar cell performance were significantly enhanced by employing the MgO-coated TiO 2 electrode. Optimized coating of a MgO layer on TiO 2 nanoparticles enhanced the energy conversion efficiency as much as 45% compared to that of the uncoated TiO 2 electrode. This indicates that controlling the extrinsic parameters such as the specific surface area is very important to improve the energy conversion efficiency of TiO 2-based solar cells. © 2005 American Chemical Society.