Electroceramics in Japan X

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Authors: Yoichi Kizaki, Yuji Noguchi, Masaru Miyayama
Abstract: Single crystals of K0.47Na0.53NbO3 (KNN) and Mn-substituted KNN (Mn-KNN, K0.53Na0.47Mn0.004Nb0.996Oy) were grown by a flux method, and the influence of lattice defects on the polarization and leakage current properties was investigated. As-grown KNN did not show an apparent polarization hysteresis loop due to its large leakage current (~10-3 A/cm2). The substitution of 0.4%-Mn at the Nb site and subsequent annealing under a moderate oxidative condition were effective in suppressing the leakage current of KNN crystals. 0.4%-Mn-KNN annealed at 1100°C in air exhibited a low leakage current (~10-8 A/cm2), a relatively large remanent polarization of 40 μC/cm2 and a coercive field of 12 kV/cm at 25°C. The oxidation of Mn and Nb ions during annealing in air is found to play an essential role in the low leakage current of Mn-KNN.
85
Authors: Keisuke Yokoh, Tomomitsu Muraishi, Song Min Nam, Hirofumi Kakemoto, Takaaki Tsurumi, Hirohiko Kumagai, Satoshi Wada
Abstract: To induce fine engineered domain configurations into potassium niobate (KNbO3) single crystals, two kinds of methods were performed, i.e., (1) high DC electric field exposure along the opposite direction of polarization of KNbO3 single-domain crystals at room temperature, and (2) introduction of randomly oriented fine domain configuration by heat treatment at 700 °C and then high DC electric field exposure along [001]c direction of KNbO3 multidomain crystals at room temperature. When the method (1) was performed, finally, the poled KNbO3 crystals became to single-domain state again through the formation of multidomain state. On the other hand, the KNbO3 multidomain crystals were obtained by using the method (2), and an enhancement of piezoelectric-related properties was observed.
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Authors: Yuji Hiruma, Yoshinori Watanabe, Hajime Nagata, Tadashi Takenaka
Abstract: The phase transition temperatures of divalent and trivalent ions substituted (Bi1/2Na1/2)TiO3 ceramics were investigated in detail by electrical measurement. BNT ceramics substituted by divalent (Ca2+, Sr2+ and Ba2+) and trivalent (La3+, Nd3+, Ho3+ and Yb3+) ions were prepared by conventional ceramic fabrication process. For these ceramics, the depolarization temperature, Td, the rhombohedral-tetragonal phase transition temperature, TR-T, and the temperature of the maximum dielectric constant, Tm, were determined on the basis of the temperature dependences of dielectric and piezoelectric properties. In this study, we demonstrated the relationship between phase transition temperature and ionic radius of ions substituted in the A-site of BNT ceramics.
93
Authors: Keisuke Satoh, Akio Sugama, Masatoshi Ishii, Masao Kondo, Kazuaki Kurihara
Abstract: Lanthanum-modified lead zirconate titanate and lead zirconate titanate epitaxial films with (100) and (111) orientations were grown respectively on (100) and (111) niobium, lending conductivity to strontium titanate through chemical solution deposition. This study investigated changes in the ordinary and extraordinary refractive index no and ne induced in these films by an electric field using the prism-coupling method. In the (100) epitaxial PZT 30/70 film, anisotropic electro-optic effects arise from the Pockels effect. The isotropic electro-optic effect, which is no = ne , was achieved on (100) epitaxial PLZT 8/65/35 and PZT 70/30 films.
99
Authors: Chuan Bin Wang, Rong Tu, Takashi Goto
Abstract: BaTi2O5 film was prepared on MgO (100) substrate by laser ablation, and the structure and electric property of the film were investigated. The film was b-axis oriented and epitaxially grown on the substrate along two in-plane directions with the a-axes ([100]-orientation) perpendicular to each other. The b-axis oriented BaTi2O5 film exhibited a sharp permittivity maximum (~ 2000) and had a high Curie temperature (750 K). The electrical conductivity increased with temperature and showed the Arrhenius relationship having an activation energy of 1.25 eV.
103
Authors: Kazuyuki Suzuki, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
Abstract: Y0.5Yb0.5MnO3 ferroelectrics/HfO2 stacking layers were successfully constructed on Si(100) substrates through the chemical solution deposition. The degree of c-axis orientation and microstructure of Y0.5Yb0.5MnO3 ferroelectrics was improved by the control of concentration of precursor solutions. Capacitance of Pt/Y0.5Yb0.5MnO3/HfO2/Si structure was almost constant over 104 s on the retention property.
107
Authors: Shogo Hayashi, Naoki Wakiya, Takanori Kiguchi, M. Tanaka, Kazuo Shinozaki
Abstract: Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) thin films were fabricated on (La,Sr)CoO3/CeO2/ YSZ coated Si substrates by double-pulse excitation PLD with and without a mask. For double-pulse excitation PLD without a mask in conditions of Nd:YAG laser irradiation before defocused KrF-excimer-laser irradiation, the surface roughness of PMN-PT thin films was rather less than that of the films fabricated using Nd:YAG single laser PLD. Thin films with smoother surfaces were deposited at the high deposition rate of 5.6 nm·min-1 using the mask and the double-pulse excitation PLD method in conditions of irradiation of Nd:YAG laser after KrF excimer laser at 0.5 =s delays.
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Authors: Tomoaki Futakuchi, Tatsunori Kakuda, Yuichi Sakai, Takashi Iijima, Masatoshi Adachi
Abstract: Bi4Ti3O12 based thick films were prepared by screen printing and firing using Pt bottom electrodes and ZrO2 substrates. The influence of excess Bi2O3 as sintering aid was investigated. Furthermore, substitution of Ti-site and Bi-site for V5+ and Nd3+ was performed. Screen-printable pastes were prepared by kneading the Bi4Ti3O12 based powder and Bi2O3 powder in a three-roll mill with an organic vehicle. The microstructures and ferroelectric properties of the thick films were examined in comparison with bulk ceramics. The remanent polarization of 9.6 μC/cm2 and coercive field of 64 kV/cm were obtained for the Bi3.0Nd1.0Ti2.99V0.01O12 thick film with 10 wt% of excess Bi2O3 fired at 1200OC.
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Authors: Hirofumi Kakemoto, Tohru Higuchi, Hajime Shibata, Satoshi Wada, Takaaki Tsurumi
Abstract: beta-FeSi2 films were prepared on Si(001) substrates by the molecular beam epitaxy method using an Fe source. The crystallographic orientation of beta-FeSi2 films on Si(001) substrates were characterized by using x-ray diffraction. Using scanning electron microscopy, surface morphology and film thickness of an oriented sample were observed and estimated. The mobility of beta-FeS2 films on Si(001) substrates was also characterized by Hall measurement at room temperature. The enhancement of figure of merit was evaluated as the functions of mobility and crystallographic orientation of samples.
121
Authors: Yuki Itoh, Masashi Satoh, Shinzo Yoshikado
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