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High Frequency Dielectric Mapping Using Un-Contact Probe for Dielectric Materials
Kakemoto, Hirofumi,Nam, Song Min,Wada, Satoshi,Tsurumi, Takaaki Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.320 No.-
<P>The microwave reflection intensity was measured at room temperature for Cu-plate, Al2O3 and SrTiO3 single crystals using a un-contact probe as a function of distance between sample and probe. The difference of reflection intensity for Cu-plate, Al2O3 and SrTiO3 single crystals was observed in the region where the distance of 0.2mm between sample and probe, and it was caused from dielectric permittivities of samples. The reflection coefficient of sample was estimated in comparison with results of electromagnetic simulation using finite differential time domain method. The reflection intensity for Cu-plate, Al2O3 and SrTiO3 single crystals was transformed to dielectric permittivity at reflection intensity minimum point. The dielectric permittivity mapping was also examined at reflection intensity minimum point.</P>
Li, Jianyong,Kakemoto, Hirofumi,Wada, Satoshi,Tsurumi, Takaaki Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.301 No.-
<P>A new measuring method and analyzing procedure were proposed to determine the complex dielectric permittivity of materials with relatively high permittivity using an RF-impedance analyzer. Samples used for the measurement were (Ba0.6Sr0.4)TiO3 and Ba(Zr0.25Ti0.75)O3 ceramics. Micro planar electrodes were used for the measurement of complex admittance of these samples. Electromagnetic simulations were carried out for determining the relative dielectric permittivity and dielectric loss. The complex dielectric permittivity vs. frequency curves of Ba(Zr0.25Ti0.75)O3 showed a broad dielectric relaxation, while that of (Ba0.6Sr0.4)TiO3 was almost flat up to 3 GHz.</P>
Satoshi Wada,H. Kakemoto,K Yokoh,T Tsurumi,T Muraishi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
The phase transition behaviors of [111]-oriented barium titanate (BaTiO3) crystals were investigated as functions of temperature, uniaxial stress, and electric field. For the phase transition caused by temperature, with decreasing temperature above Tc, the paraelectric phase changed to an intermediate phase with a superparaelectric state and finally changed to a ferroelectric phase with randomly oriented spontaneous polarizations. Moreover, the phase transition caused by the uniaxial stress field above Tc was found to be almost similar to the one caused by temperature. On the other hand, for the phase transition caused by an electric field above Tc, with increasing electric field, the paraelectric phase changed to an intermediate phase and finally to a ferroelectric phase with an oriented polar direction. These results suggest that above Tc, a combination of uniaxial stress with an electric field may be effective as a poling treatment for BaTiO3 crystals. Thus, in this study, a new poling method for the BaTiO3 crystals by using control of the temperature, the uniaxial stress, and the electric field is proposed.t
Piezoelectric Properties of Potassium Niobate Single Crystals by Domain Engineering
S. Wada,H. Kumagai,H. Kakemoto,K. Muraoka,T. Tsurumi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Potassium niobate (KNbO3) single crystals were grown by a TSSG method. At rst, the electric eld was applied along the [001]c (cubic notation system) direction of KNbO3 crystals to induce the engineered domain congurations into KNbO3 crystals. Prior to domain engineering, the piezoelectric properties of [001]c-oriented KNbO3 single-domain crystals were measured. These measurement values were completely consistent with the calculated apparent d31 and d32. Finally, the engineered domain congurations were induced into KNbO3 crystals. As a result, piezoelectric properties increased with decreasing domain sizes of the engineered domain conguration. However, the symmetry of the KNbO3 crystals was mm2, and there were four kinds of domain structures such as 90,180, 60 and 120 domains. Thus, the engineered domain structure induced in this study was very complicated, and the piezoelectric properties were also ependent on domain pattern and kinds of domain walls.
Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles
Satoshi Wada,C Moriyoshi,H. Yasuno,K Kakemoto,K Takizawa,M Ohishi,T Hoshina,T Tsurumi,Y Kuroiwa 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Barium titanate (BaTiO3) nanoparticles with various particle sizes from 17 to 1,000 nm were prepared by using the 2-step thermal decomposition method of barium titanyl oxalate under various degree of vacuum. Various characterizations revealed that these particles were impurity-free, defectfree, dense BaTiO3 nanoparticles. When the degree of vacuum was high (pressure of 150 Pa at 650 C), the dielectric constant of BaTiO3 particles with a size of around 60 nm exhibited a maximum of around 15,000. On the other hand, when the degree of vacuum was low (pressure of 400 Pa at 650 C), no dielectric maximum was observed. To explain this size dependence, we precisely investigated a particle structure by using synchrotron radiation. As a result, the particles were always composed of two layers, i.e., a surface cubic layer and a bulk tetragonal layer, and the thickness of the surface cubic layer decreased with increasing degree of vacuum during the preparation of BaTiO3 nanoparticles. Thus, we confirmed that the surface structure was an important factor in determining the dielectric properties of BaTiO3 nanoparticles.
Tsurumi, Takaaki,Nam, Song-Min,Mori, Naoko,Kakemoto, Hirofumi,Wada, Satoshi,Akedo, Jun The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.8
The Aerosol Deposition (AD) process will be proposed as a new fabrication technology for the integrated RF modules. $\alpha$-A1$_2$O$_3$ thick films were successfully grown on glass and Al substrates at room temperature by the AD process. Relative dielectric permittivity and loss tangent of the $Al_2$O$_3$ thick films on Al showed 9.5 and 0.005, respectively. To form microstrip lines on aerosol-deposited A1903 thick films, copper electroplating and lithography processes were employed, and the square-type cross section with sharp edges could be obtained. Low-pass LC filters with 10 GHz cutoff frequency were simulated by an electromagnetic analysis, exhibiting the validity of the AD process as a fabrication technology f3r integrated RF modules.
Fabrication of Microstrip Band Pass Filters in GHz Region by Aerosol Deposition Process
Momotani, Mihoko,Mori, Naoko,Nam, Song Min,Kakemoto, Hirofumi,Wada, Satoshi,Tsurumi, Takaaki,Akedo, Jun Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.301 No.-
<P>In order to fabricate a microstrip band pass filter in GHz region as a passive component of RF modules, Al2O3 thick films were prepared on Cu metal substrates by AD (Aerosol Deposition) process. The dimensions of the filters were determined by the high frequency electromagnetic analysis. The filters were successfully fabricated on AD-derived Al2O3 thick films by employing sputtering, photolithography, electroplating and chemical etching processes. Their filtering characteristics were examined by a Network Analyzer. Through this work, we suggest that the AD process will be important the fabrication technology for integrated RF modules.</P>