Takahiro Yamakawa

Electrical conductivity and mechanical properties of alumina-dispersed doped lanthanum gallates

Abstract With the aim of increasing the mechanical strength of doped lanthanum gallate ceramics, which can be applied to the electrolyte in solid oxide fuel cells for reduced temperature operation, the effects of alumina dispersion on mechanical and electrical properties were investigated. The thermal expansion coefficient showed no significant changes either with the amount of alumina addition or with the oxygen partial pressure in the atmosphere. The alumina dispersion preferably along grain boundaries was found to be effective in retarding the grain growth of lanthanum gallate, which greatly increased the bending strength at both room temperature and 800°C. The sample with 2 wt% of alumina addition showed electrical conductivity comparable to that of the perovskite matrix alone at 800°C and higher conductivity at temperatures lower than 750°C. At additions of ≥5 wt%, the alumina grains partially blocked the transport of oxide ions between the lanthanum gallate grains, which decreased the ionic conductivity to unacceptable levels. The optimum alumina addition for the improvement of mechanical properties without altering the thermal expansion coefficient and ionic conductivity was found to be around 2 wt%. A single-cell using the electrolyte sheet with the optimized composition showed a maximum power density of 0.245 W/cm2 at 800°C.

Highly Reliable Piezoelectric Actuator for Precision Stage System

A highly reliable nonresonant ultrasonic motor (NRUSM) made of cylindrical piezoelectric material is proposed in this paper. The high reliability is characterized by long lifetime and no outer gas in the vacuum environment, which are ensured by not using stack adhesives as the source of the gas emission. Positioning and tracking accuracy was better than below ±2 nm. The structural design is discussed in terms of the application to a high-speed high-precision stage system which has stable response to frequent biases without interference from resonant phenomena and the required mechanical strength.

Finite Element Method Analysis of Piezoelectric Transformer

FEM analysis (finite element method) was applied in order to find out the method of controlling spurious vibration, which is generated during piezoelectric transformer use. When the length, width, and thickness of an element are changed, eigen frequency of both drive longitudinal resonance vibration (specifically primary mode) and spurious vibration changes. The optimal design size was found by using the fact that the rate of change differed with vibration type. The eigen frequency (natural frequency) of spurious vibrations obtained from FEM analysis and the surveyed elements were in agreement. By changing the element size parameters, we were able to design an element that decreased spurious vibration. INTRODUCTION The demand for a piezoelectric transformer has diversified in recent years, and it has been necessary to customize the product for each customer. Moreover, since a piezoelectric transformer is used for the liquid crystal backlights of laptop computers, there is a strong demand for shortened development period. In order to cope with these demands, we are using FEM (finite element method) simulation analysis technology to study piezoelectric transformer development. Natural frequency analysis (modal analysis) of a piezoelectric transformer has often been performed recently using FEM. In this report, FEM analysis of the method of removing spurious vibration from the drive frequency was carried out. It aims to clarify the design technique for optimizing size of a piezoelectric transformer, which has not been done until now. EXPERIMENT An example of the model used for analysis is shown in Fig. 1. This is a Rosen type piezoelectric multilayered transformer (a thickness of 1.7-2.2mm, a length of 24.0-26.0mm, a width of 7-9mm), with the polarization of the input side being carried out in the thickness direction, and the output side being carried out in the longitudinal direction. Modal analysis was also performed for the drive frequency range (50kHz 80kHz). To determine if the frequency that was calculated by FEM in fact generated spurious vibration, we performed a vibration speed measurement at low Key Engineering Materials Online: 2003-08-15 ISSN: 1662-9795, Vol. 248, pp 35-40 doi:10.4028/www.scientific.net/KEM.248.35

Development of nonresonant ultrasonic motor with sub-nanometer resolution

Precise positioning, which is the base technology for ultra-precise treatments, is highly essential in semiconductor LSI circuits, bio-cells, molecular sensors, and quantum devices. Conflicting performances, high-speed, long-stroke, and high-resolution have been achieved by using die nonresonant ultrasonic motor (NRUSM) controlled under the piezoelectric effect. One of the notable features of the NRUSM is do the frequency of the driving voltage can be varied in a wide range, which means the motion control of the NRUSM can be done by both the amplitude and frequency The maximum stage feed velocity is 140 mm/s with average acceleration of 2200 mm/s/sup 2/ in the 100 mm stroke under open-loop control. 100 nm step response with /spl plusmn/0.69 nm positioning accuracy is completed in 0.35 s under closed-loop control.

The Effect of Ag and PbO on Sintering Behavior of PbSr(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3

The effect of Ag and PbO on the sintering behavior and the piezoelectric properties of PbSr(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 system has been studied. A small addition of Ag enhances the value of er. and Kr. In the specimen with Ag addition, the grain growth was observed by use of SEM. The shrinkage vs temperature curves showed that the shrinkage of the specimen with Ag addition abruptly increases from 900°C and the value of shrinkage at 1100°C is as twice as the additive-free specimen. The shrinkage vs time plots revealed that the grain boundary diffusion is dominant on the sintering of PMN-PZT with Ag and Pb addition.

The Influence of MnCO3 Addition on the Sintering Behavior of PZT Ceramics

The influence of MnCO3 addition on the sintering behaviour of PZT ceramics was investigated. In proportion as amount of MnCO3 addition increased, the relative density of sintered body decreased. The shrinking curves during sintering showed the following features ; Starting temperature of shrinking shifted higher as amount of MnCO3 addition increased. These shrinkages were able to classify into two stages;at the first stage, the shrinking speeds of specimen were relatively slow, but at the second stage, those were rapid. Achieved shirinkage values of each specimen were corresponding to the relative densities. The grain growth behaviour was investigated with SEM micrographs. On the specimen with 0.4wt% MnCO3, rapid grain growth occurred only between 1050°C and 1150°C, but slow grain growth continued over 1150°C.On the specimen with 0.8wt% MnCO3, grain growth did not occured till 1150°C, but rapid grain growth continued over 1150°C. We conclude that the MnCO3 is not useful for PZT ceramics as a sintering aid.