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© 2020 The Japan Society of Applied Physics. Microrod-type CoFe2O4(CFO)/Bi3.25Nd0.65Eu0.10Ti3O12(00ℓ) (BNEuT) composite thin films were fabricated by a combination of high-temperature sputtering, reactive ion etching, and metal organic chemical vapor deposition (MOCVD) on Pt(100)/MgO(100) substrates. The substrate temperature for MOCVD was varied from 450 °C to 600 °C to examine its effect on the structural, magnetic, and ferroelectric properties. The substrate temperature affects the compressive stress at the interface between the CFO and BNEuT. The surface morphology changed drastically above 550 °C. The room temperature magnetization-magnetic field hysteresis loops for the films showed clear ferromagnetic hysteresis loop and magnetic shape anisotropy. The room temperature polarization-electric field (P-E) hysteresis loops for the films showed a clear ferroelectric hysteresis loop, and slightly leaky P-E hysteresis loop. The coercive field increased slightly with increasing substrate temperature. Judging from the structural, ferromagnetic, and ferroelectric properties, the film deposited at 550 °C has potential as an excellent multiferroic material.

Using a a-axis-oriented epitaxial (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT) thin films with a microplate-like shape as a ferroelectric pillar material, micropillar-type CoFe2O4 (CFO)/BNEuT(h00)/Nb:TiO2(101) composite multiferroic films were fabricated by metal organic chemical vapor deposition. The deposition time was varied from 90-150 min to examine its effect on the structural, ferroelectric, and ferromagnetic characteristics of the films. All the films exhibit single-phase cobalt ferrite with a cubic inverse-spinel structure. The deposited CFO films have a similar columnar structure with a comparatively good step coverage of 37%-66%. The room-temperature magnetization-magnetic field hysteresis loop of the films showed a clear ferromagnetic hysteresis loop, and coercivity decreased from 1.1 to 0.9 kOe with increasing the deposition time. The room-temperature polarization-electric field hysteresis loop of the films showed a ferroelectric hysteresis loop, and the effect of the leakage current was the smallest for a deposition time of 120 min.

© 2019 The Japan Society of Applied Physics. Highly c-axis oriented (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT) thin films were deposited on the Pt(100)/MgO(100) substrates by high-temperature sputtering. The substrate temperature was varied from 550 °C to 650 °C to examine its effect on the structural, dielectric, ferroelectric, and piezoelectric characteristics of the films, and consequently find the optimal substrate temperature for heteroepitaxial growth of BNEuT thin films. All the films deposited at 580 °C-650 °C exhibited a high degree of c-axis orientation [α (00l)] of ≥97%. All the films grown heteroepitaxially on Pt(100)/MgO(100) substrates was rotated by ±45° with respect to the underlying substrates and had a mainly upward polarization, based on data observed by piezoresponse force microscopy. Judging from the structural, dielectric, ferroelectric, and piezoelectric characteristics, it is shown that the optimal substrate temperature for heteroepitaxial growth of BNEuT films with a high α (00l) of >97% and a comparatively large remanent polarization of 2.0 μC cm-2 is 580 °C.

A monoclinic ferroelectric phase with the space group Pm has been discovered in lead-free (Na0.5K0.45Li0.05) NbO3 solid solution ceramics synthesized by a malic acid complex solution method. At ambient temperature, the lattice parameters of this monoclinic structure were (a(m), b(m), c(m); beta) = (4.002 angstrom, 3.935 angstrom, 3.980 angstrom, 90.32 degrees). The average and local structures of this monoclinic phase were analyzed by synchrotron X-ray measurements. The average structure maintained the monoclinic structure down to 20 K, although the local structure changed below room temperature. The distinct short-range order structure was found to be rhombohedral. The results demonstrate the presence of an order-disordertype phase transition structurally bridging between the rhombohedral local structure and the low-symmetry monoclinic average structure in a (Na0.5K0.45Li0.05) NbO3 solid solution system. (C) 2017 The Japan Society of Applied Physics

Regardless of the deposition time (30-90 min), almost single-phase magnetite (Fe3O4) films with a cubic inverse-spinel structure were produced at a substrate temperature of 500 degrees C by metalorganic chemical vapor deposition (MOCVD). The Fe3O4/(Bi(3.25)Nd(0.65)Eu(0.1)0) Ti3O12 (BNEuT) composite film deposited at 500 degrees C for 90 min by MOCVD exhibited excellent room-temperature magnetic properties, such as a saturation magnetization of 480 emu/cm(3), a residual magnetization of 160 emu/cm(3), and a coercivity of 297 Oe. Ferromagnetic Fe3O4 electrodes micropatterned using a combination of photolithography and reactive ion etching were fabricated after MOCVD, and their structural, leakage current, and ferroelectric characteristics were investigated. The room-temperature leakage current density-applied electric field and polarization-electric field (P-E) characteristics of the composite films were successfully measured using Fe3O4 electrodes. The room-temperature P-E hysteresis loop for a sample with the structure Fe3O4/BNEuT/Nb: TiO2/Ti had a relatively good shape, with a remanent polarization of 8 mu C/cm(2) and a coercive field of 193 kV/cm. (C) 2017 The Japan Society of Applied Physics

Polycrystalline powder samples of the zinc-substituted strontium cobalt Z-type hexaferrite: Sr3Co2-xZnxFe24O41 (x = 0, 0.5, 1.0, 1.5 and 2.0) were prepared by the polymerizable complex method. Their Mossbauer spectra were measured at room temperature with conventional constant-acceleration spectrometer. Obtained Mossbauer spectra were numerically separated into six discrete components. The relationship between Mossbauer parameters and magnetic properties has been discussed. From the values of the isomer shift, it was found that the iron ion in Sr3Co2-xZnxFe24O41 is trivalent with high spin. The value of the quadrupole splitting increased and changed the sign from negative to positive for the sample with x = 1.5. From the results mentioned above and the analysis of the complex permeability spectra, the magnetocrystalline anisotropy of Sr3Co2-xZnxFe24O41 is changed from c-plane to c-axis at Zn content between x = 1.0 and 1.5. The compositional dependence of the areas of each subspectra showed that Zn2+ ions occupy the sites with down spin at the compositional range of x = 0.0-1.0.

<p>To develop high-performance materials for high-power piezoelectric applications, ternary high-density solid solutions with compositions of xPb(Zr_0.52Ti_0.48)O₃−yPb(Mn_1/3Sb_2/3)O₃−zPb(Zn_1/3Nb_2/3)O₃ (PZT_xPMS_yPZnN_z) with x = 0.82−0.96, y = 0.02−0.16, and z = 0.02−0.16, were fabricated by a conventional solid-state reaction method. A detailed investigation was carried out into the microstructure and crystal structure of the samples, together with their piezo- and ferroelectric properties. It was found that a solid solution with x = 0.86, y = 0.085, and z = 0.055 and a rhombohedral structure exhibited excellent piezo- and ferroelectric properties. These included piezoelectric coefficients d₃₃ (longitudinal length mode) = 170 pC/N and -d₃₁ (transverse length mode) = 69 pC/N, a mechanical quality factor Q_m(p) (radial mode) = 2218, d₃₃⋅Q_m(p) = 376×10³ pC/N, -d₃₁⋅Q_m(p) = 133×10³ pC/N, electromechanical coupling factors k_p (radial mode) = 46% and k₃₁ (transverse length mode) = 28%, a Curie temperature T_c = 259℃ a remanent polarization 2P_r = 53 μC/cm², and a coercive field 2E_c = 34 kV/cm. Thus, this is a highly promising piezoelectric material for high-power ultrasonic vibrators and piezoelectric transformers.</p>

<p>(Na_0.50K_0.45Li_0.05)NbO₃ (NKLN) powder was synthesized by the malic acid complex solution method, and NKLN solid solutions were then fabricated at firing temperatures of 900−1050℃ using a conventional solid-state reaction technique. The piezoelectric properties of the resulting materials were measured, and samples produced at 950℃ were found to exhibit the maximum d₃₃ and k_p values of 151 pC/N and 32%, respectively. On the basis of a local structural analysis using high-energy X-ray diffraction, the distortion of NbO₆ octahedra, which is the origin of the ferroelectric properties, also exhibited a maximum at 950℃. Thus, this is the optimal firing temperature for fabricating NKLN samples with excellent piezoelectric properties and the largest NbO₆ octahedral distortion.</p>

<p>NaNbO3は非常に複雑な相転移系列を持つ。室温では反強誘電的な結晶構造を持ちながら、しばしば強誘電性が観測されている。また、室温以下では斜方晶構造から菱面体晶構造への相転移点があるが、この相転移は散漫的で広い温度領域で2相が共存する。我々は散漫的な相転移の原因はNaNbO3の局所構造にあると考えており、ユニットセル内のランダムネスが解消される際に相転移が起こると予想している。今回、この仮定を確かめるために、種々の手法で作製し、相転移の振る舞いの異なるサンプルを用いて、局所構造と相転移の関係を明らかにしたところ、我々の仮定と矛盾しない結果が得られたのでこれを報告する。</p>

© 2015 The Japan Society of Applied Physics. (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT-0.1) films with a- and b-axis orientations and thicknesses of 1.8-2.3μm were sputter-deposited on conductive Nb:TiO2(101) substrates containing 0.79 mass% Nb. The deposition temperature was fixed at 650 °C, and the sputtering gas pressure was varied from 0.4 to 5.0Pa in order to examine its effect on the structural, ferroelectric and piezoelectric properties of the films. The films were found to have a mostly single-phase orthorhombic structure, with a high degree of a- and b-axis orientations (93-98%). The films had a nanoplate microstructure, with the plates being aligned along the [100]/[010] direction, and porosities of 15-25%. A maximum room-temperature remanent polarization (2Pr) of 93 μC/cm2 was obtained for a sputtering gas pressure of 5.0 Pa. All the films were strongly a-axis oriented, according to the results of X-ray diffraction measurements and vertical amplitude images in piezoresponse force microscopy. The optimal sputtering gas pressure for heteroepitaxial growth of BNEuT-0.1 nanoplates with a high degree of a-axis orientation of 96.5%, a maximum orthorhombicity of 0.0017, a comparatively large remanent polarization of 2Pr = 66 μC/cm2, and a high porosity of 24% was found to be 0.4 Pa.

The piezoelectric properties of high-temperature-poled high-density solid solutions with compositions of xPb(Mn1/3Nb2/3)O-3 yPbZrO(3)-zPbTiO(3) (xMnN-yPZ-zPT; PNInNZT) with x = 0.020 - 0.180, y = 0.420 - 0.580, and z = 0.400 - 0.560 were investigated by using the resonantantiresonant frequency method. The two optimal compositions that exhibited large values of d(33).Q(m)(p), where d(33) is the piezoelectric coefficient (longitudinal length mode) and Q(m)(p) is the mechanical quality factor (radial mode) for high-power piezoelectric applications were x = 0.040, y = 0.540, and z = 0.420 in the rhombohedral and the morphotropic phase boundary (MPB) regions and x = 0.095, y = 0.435, and 2 = 0.470 in the MPB and the tetragonal regions. By comparing the maxima in d(33).Q(m)(p) for high-temperature (HT)-poled PIVInNZT samples with the maxima in d(33) . Qm(p) for room-temperature (RT)-poled PMnNZT samples that had been previously reported, the ratio of d33 Qm(p)HT/d33 .Qm(p) RT was approximately 1.8, exhibiting a significant iniprovement due to HT-poling treatments.

High-density solid solutions with compositions of (1-x)(Bi1/2Na1/2)TiO3-xBa(Mn1/3Nb2/3)O-3 (BNT-BMN), with x = 0 - 0.06, were prepared by using the conventional ceramic fabrication process. The optimal composition that yielded the best piezoelectric properties for high-power piezoelectric applications was investigated. X-ray diffraction (XRD) analyses of BNT-BMN with x = 0 - 0.06 suggested that the rhombohedral-pseudocubic morphotropic phase boundary (MPB) for this material system is in the compositional region 0.035 a parts per thousand currency sign x a parts per thousand currency sign 0.04 at room temperature. A hard-mode BNT-BMN with x = 0.03, which lay on the rhombohedral side near the MPB region, exhibited excellent piezo- and ferroelectric properties.

© 2014 The Japan Society of Applied Physics. Epitaxial BiFeO3(BFO) thin films with striped- and single-domain structures have been grown on SrTiO3(STO) (103) and (113) substrates by radiofrequency planar magnetron sputtering. The domain structure of BFO was controlled by the orientation of the STO substrate. Piezoelectric force microscopy revealed that BFO thin films on STO (103) and STO (113) had a striped-domain structure with 71° domain walls running along o010pSTO, and a single-domain structure, respectively. To confirm the photovoltaic property, rectangular Pt electrodes with widths of 150-200μm were deposited on BFO surfaces with interelectrodes distances of 200-250 μm. I-V characteristics were measured under an illumination of a collimated violet laser (γ = 405nm) with a power density of 380W/cm2. In the striped-domain-structure BFO film with Pt electrodes fabricated along domain walls, above-band-gap open-circuit voltage (VOC) of 29V was observed. In addition, single-domain-structured BFO thin film with Pt electrodes fabricated along h &lt;1¯10&gt; also showed above-band-gap Vocof 26V despite the absence of domain walls. It is considered that these large Vocvalues originated from the photovoltaic effect not at the domain walls but in bulk BFO.

© 2014 The Japan Society of Applied Physics. Sr2Bi4Ti5O18(SBTO) films with a- and b-axis orientations, and thicknesses of 0.9-1.2μm were sputter-deposited on conductive Nb:TiO2(101) substrates containing 0.79 mass% Nb. The deposition temperature was varied from 575 to 700 °C under a fixed gas pressure of 0.4 Pa, and the structural and ferroelectric characteristics of the films were investigated. SBTO films deposited at 625-700 °C had a mostly single-phase orthorhombic structure, with a high degree of a- and b-axis orientations [α(h00)/(0k0)] of 99.0-99.8%. In addition, the full width at half maximum of the (200) diffraction peak was 0.69-0.86°, which indicated good crystallinity. SBTO films deposited at 625-650 °C had a nanoplate-like microstructure with the plates aligned along the [010] direction. The real room-temperature remanent polarization (2P∗r), taking the porosity between the nanoplates into account, exhibited a maximum of 40 μC/cm2at 650 °C. Thus, the optimal deposition temperature for heteroepitaxial growth of SBTO nanoplates with a high α(h00)/(0k0)of ≥99.0% and excellent ferroelectric properties on conductive Nb:TiO2substrates is 650 °C under a gas pressure of 0.4 Pa.

Recently, the semiconducting characteristics of BiFeO3 thin films such as the photovoltaic effect or diode characteristics have been extensively investigated. However, the current conduction mechanism has not been completely clarified yet. In this study, the current conduction mechanism of the ideal BFO thin film, which has a single domain without conduction domain walls, such as 71 and 109° domain walls, has been investigated. The current density-electric field (J-E) characteristics of 100- to 1000-nm-thick BFO thin films and their temperature dependence in the range of 100-260K have been carefully investigated. From these thickness and temperature dependences of the J-E characteristics, it can be concluded that the most probable mechanism of current conduction in the single-domain BFO thin film is space-charge-limited current (SCLC) with a shallow trap. © 2014 The Japan Society of Applied Physics.

Rhombohedral (R-) and tetragonal-like (T-) BiFeO3(BFO) mixed-phase thin films and single R-phase BFO thin films have been grown on SrRuO3-buffered SrTiO3(STO) (001) substrate by ion beam sputtering. From X-ray diffraction study, it was found that T-BFO and R-BFO mixed-phase thin films can be grown at a low oxygen partial pressure of 1mPa, and the lattice parameters of the T-BFO and R-BFO were a = 0.381 nm, c = 0.461nm (c/a = 1.22), and a = 0.394nm and c = 0.400nm (c/a = 1.02), respectively. High-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observation and energy dispersive X-ray analysis (EDXA) mappings have revealed a clear T-BFO lattice and a-c domain in the middle of the thin films. However, Bi-rich and Fe-rich secondary phases were also found with the T-BFO phase. Therefore, it can be concluded that secondary phases such as Bi2O3or Bi-poor phase are needed for T-BFO formation on STO (001) substrate, and the a-c domain formation does not occur by stress relaxation but matching of the growth directions of different domains. © 2014 The Japan Society of Applied Physics.

a- and b-axis-oriented (Bi3.25Nd0.75-xEu x)Ti3O12 (BNEuT, x = 0-0.75) films of 3.0μm thickness were fabricated on conductive Nb:TiO2(101) substrates containing 0.79 mass-Nb by high-temperature sputtering at 650°C, and their structural and piezoelectric characteristics were investigated. The room-temperature remanent polarization (2Pr) and effective piezoelectric coefficient (d33) values for the BNEuT films exhibited maxima of 87 μC/cm2 and 15pm/V, respectively, at x = 0.10, which were approximately 1.3 times larger than those (2Pr = 65 μC/cm2 and d33 = 12pm/V) of the nondoped (Bi 3.25Nd0.75)Ti3O12 (BNT) nanoplate. The BNEuT film with x = 0.10 had a high a-axis orientation judging from the X-ray diffraction measurement and the observation of the phase image by piezoresponse force microscopy. It is shown that adequate Eu3+ doping of BNT nanoplates produces a larger displacement magnitude of the octahedra than that in the nondoped BNT nanoplate, resulting in an improvement of piezoelectric properties in addition to the ferroelectricity. © 2014 The Japan Society of Applied Physics.

Single-domain BFO thin films are prepared on a SrRuO3-buffered SrTiO3 (STO) (001) substrate by RF planar magnetron sputtering. A domain structure is controlled by vicinal direction of the STO substrate. The BFO thin films on vicinal STO along 〈110〉 show single-domain structure without any domain walls. To confirm the influence of epitaxial strain on lattice distortion and ferroelectricity, single-domain BFO thin films with thicknesses ranging from 10-1000 nm are prepared. Synchrotron X-ray diffraction reveals that lattice relaxation and step bunching occur in the thickness range of 50-200 nm. The BFO films with thicknesses over 300 nm are almost free from the influence of the epitaxial strain induced by (001)-oriented substrates. The remanent polarization Pr is almost constant at about 60 μC/cm 2. However, Pr slightly increases in the BFO films with thicknesses less than 200 nm. Even the 100-nm-thick BFO film show fully saturated D-E hysteresis at RT, and the Pr is 65 μC/cm 2. © 2013 The Japan Society of Applied Physics.

a- and b-axis-oriented (Bi3.25Nd0.75-xEu x)Ti3O12 (BNEuT, x = 0-0.75) films of 3.0 μm thickness were fabricated on conductive Nb:TiO2(101) substrates containing 0.79 mass% Nb by high-temperature sputtering at 650 °C, and their structural and ferroelectric characteristics were investigated. All the films had a mostly single-phase orthorhombic structure, with high degrees of a- and b-axis orientations of 99.0-99.8%. The lattice parameters (a-, b-, and c-axis lengths) and the calculated orthorhombic lattice distortion decreased monotonically with increasing Eu content. The microstructure of BNEuT films with x = 0-0.50 was nanoplate-like, whereas that of films with x ≥ 0:60 was significantly more bulklike. The real room-temperature remanent polarization (2Pr*), taking the porosity between the nanoplates into account, had a maximum value of 2Pr* = 87 μC/cm2 at x = 0.10, which was approximately 1.3 times larger than that (65 μC/cm2) of the nondoped BNT film. It is shown that lattice distortion caused by rotation of octahedra in the a-b plane due to the Eu substitution plays a significant role in the improvement of ferroelectricity. © 2013 The Japan Society of Applied Physics.

The morphotropic phase boundary (MPB) for high-density solid solutions with compositions of xPb(Mn1/3Nb2/3)O-3-yPbZrO(3)-zPbTiO(3) (PMnNZT) with x = 0.02-0.16, y = 0.42-0.56, and z = 0.42-0.56 has been refined on the basis of an analysis of the dielectric and piezoelectric properties of the fabricated samples. An X-ray diffraction analysis of the PMnNZT solid solutions suggested that the refined rhombohedral-tetragonal MPB in this material system is in the compositional region x = 0.02-0.134, y = 0.42-0.54, and z = 0.44-0.485. It was found that a hard-mode solid solution with x = 0.10, y = 0.45, and z = 0.45, which lies in the refined MPB region, exhibited excellent piezo- and ferroelectric properties highlighting its potential as a high-power piezoelectric material for ultrasonic vibrators and piezoelectric transformers. (C) 2013 The Japan Society of Applied Physics

a- and b-axis-oriented Bi3. 25Nd0. 75Ti3O12 (BNT) nanoplates, 3. 0-μm thick, were fabricated on conductive Nb:TiO2(101) substrates with 0. 79 mass% Nb at 650 °C by high-temperature sputtering. Successively, the fabrication of inorganic-organic composites was carried out by introducing an epoxy resin to the spaces between the BNT nanoplates. The fourier transform infrared spectroscopy (FTIR) and the energy dispersive X-ray (EDX) elemental mapping results confirmed that the fabricated composites were inorganic-organic hybridized materials with cured epoxy resin introduced into the spaces between the BNT nanoplates. Piezoelectric response measurements of the fabricated BNT-epoxy resin composites by using piezoresponse force microscopy (PFM) showed that the composites have potential as piezoelectric microelement materials. © 2013 The Korean Physical Society.

Electrochemical oxygen reduction behavior for a half cell composed of a mixed ionic and electronic conducting (MIEC) oxide and an oxygen excess-type solid electrolyte was investigated. A perovskite-type MIEC oxide, (La0.6Sr0.4)(Co1-yFey)O3-delta (LSCF), was employed as a base material for an electrode catalyst of oxygen reduction reaction. As an electrolyte, Al-doped lanthanum silicate [La-10(Si5.8Al0.2)O-26.9 (ALSO)] was used, which is a new class of oxide ion conductors with apatite-type structure. The evaluated polarization resistance, R-pol, for the reaction largely depended on y, and the minimum resistance was obtained for y = 0.2. The R-pol value was 0.3 Omega cm(2) at 1073 K in ambient air [P(O-2) = 2.1 x 10(4) Pa] for y = 0.2. To improve the performance, introduction of silver nano-particles onto the LSCF particles was studied. With the Ag-modification, R-pol at 1073 K could be minimized toward 0.08 Omega cm(2). The cathodic overpotential of the electrode evaluated from DC polarization at 1073 K was 18 mV at 0.1 A cm(-2). (C) 2012 Elsevier B.V. All rights reserved.

Ferroelectric BaTiO3and antiferromagnetic BaFeO3 are deposited alternatively by a pulsed laser deposition method with the aim of fabricating room-temperature multiferroic materials. X-ray diffraction (XRD) analysis reveals that the superlattice structure is fabricated with a designed periodicity and thin film quality is improved by increasing BaFeO3 layers. Ferroelectricity and ferromagnetic properties are examined by the double-wave method (DWM) of D-E hysteresis loops, an XRD dilatometry, and a superconducting quantum interference device magnetometer. Our superlattice thin film shows multiferroicity, i.e., the coexistence of ferroelectricity and ferromagnetism, at room temperature. © 2012 The Japan Society of Applied Physics.

海水中のセシウムイオンを除去するための無機イオン交換体をカキ殻や浄水汚泥およびガラスなどの無機廃棄物から合成した。海水中でのセシウムイオン除去率は72％であった。本吸着材は天然ゼオライトと比べて迅速にセシウムイオンを吸着することが判明した。

BiFeO₃(BFO) thin films with various Bi/Fe ratios have been deposited on SrRuO₃/SrTiO₃(001) substrates by dual ion beam sputtering. A Bi₂O₃ceramic disk and an $\alpha$-Fe₂O₃powder disk were used as targets, and simultaneously sputtered using a dual ion beam. Bi/Fe ratio has been controlled by adjusting the beam current ratio on the Bi₂O₃- and $\alpha$-Fe₂O₃-side ion sources. Even a BFO thin film with a Bi/Fe ratio of 0.95 and a smooth surface shows a slightly leaky characteristic. $[\text{Fe$^{2+}$}]/([\text{Fe$^{3+}$}]+[\text{Fe$^{2+}$}])$ ratio has been estimated by Auger electron spectroscopy (AES). From the AES profiles, the $[\text{Fe$^{2+}$}]/([\text{Fe$^{3+}$}]+[\text{Fe$^{2+}$}])$ ratio of the BFO thin film with a Bi/Fe ratio of 0.95 is estimated to be 0.14. It is considered that not only improving surface roughness but also enhancing oxidization is important for reduction in leakage current.

BiFeO3 (BFO) thin films with various Bi/Fe ratios have been deposited on SrRuO3/SrTiO3/SrTiO3(001) substrates by dual ion beam sputtering. A Bi2O3 ceramic disk and an α-Fe2O3 powder disk were used as targets, and simultaneously sputtered using a dual ion beam. Bi/Fe ratio has been controlled by adjusting the beam current ratio on the Bi2O 3- and α-Fe2O3-side ion sources. Even a BFO thin film with a Bi/Fe ratio of 0.95 and a smooth surface shows a slightly leaky characteristic. [Fe2+]/(Fe3+]+ [Fe2+]) ratio has been estimated by Auger electron spectroscopy (AES). From the AES profiles, the [Fe2+]/(Fe3+]+ [Fe2+]) ratio of the BFO thin film with a Bi/Fe ratio of 0.95 is estimated to be 0.14. It is considered that not only improving surface roughness but also enhancing oxidization is important for reduction in leakage current. © 2011 The Japan Society of Applied Physics.

3.0-mu m-thick a- and b-axis-oriented (Bi3.25Nd0.75)Ti3O12 (BNT-0.75) films were fabricated on conductive Nb:TiO2(101) (Nb = 0, 0.048, 0.46, 0.79 mass%) single crystal substrates by high-temperature sputtering. BNT films grown on undoped TiO2 substrates have no orientation, whereas BNT films deposited on Nb:TiO2 substrates with 0.46-0.79 mass% Nb show strong (h00/0k0) diffractions and grow with a heteroepitaxial relationship to the underlying Nb:TiO2 substrates. The BNT-0.75 film deposited on a Nb:TiO2(101) substrate with 0.79 mass% Nb exhibited the peculiar shape of approximately 100- to 150-nm-thick nanoplates. We speculate that the driving force for producing a plate-like structure for BNT films is the large anisotropy of the linear expansion coefficients for Bi4Ti3O12, and the comparatively small lattice matching between the Nb:TiO2 substrate and the BNT film.

a- and b-axis-oriented (Bi3.25Nd0.75)Ti3O12 (BNT) films, 2.4 - 2.8 mu m thick, were fabricated on conductive IrO2(101)/Al2O3(012) and Nb:TiO2(101) [Nb = 0, 0.05, and 0.79 mass%] substrates by high-temperature sputtering. A BNT film grown on an IrO2(101)/Al2O3(012) substrate had low crystallinity [full width at half maximum (FWHM): Delta theta = 2.83 degrees], low degrees of a- and b-axis orientations [alpha((h00/0k0)) = 49.2%] and dense microstructure in which a- and b-axis-oriented crystals existed locally in the film, while a BNT film grown on a Nb:TiO2(101) substrate with 0.79 mass% Nb showed high crystallinity (Delta theta = 0.57 degrees), a high alpha((h00/0k0)) (99.9%) and a porous microstructure comprised of many nanoplate-like crystals. The BNT film grown with a heteroepitaxial relationship to the underlying Nb:TiO2 substrate is shown to have a symmetric loop shape, with a remanent polarization (2P(r)) of 29 mu C/cm(2) and a coercive field (2E(c)) of 297 kV/cm.

Perovskite-structured solid solutions with compositions of 0.9963{(1 - x)(Bi1/2Na1/2)TiO3-xBa(Cu1.1/3Nb2/3)O-3} + 0.0037MnO(2), with x = 0-0.06 [abbreviated as (1 - x) BNT-xBCN)], were fabricated by normal sintering, and their structural, and piezo- and ferroelectric properties were investigated in detail. The X-ray diffraction profiles of the (1 - x) BNT-xBCN solid solutions with x = 0-0.06 suggested that the rhombohedral-tetragonal morphotropic phase boundary (MPB) in this material system is in the compositional region x = 0.0425-0.0460. The cross-sectional transmission electron microscopy (TEM) images and selected-area electron diffraction (SAED) patterns of the (1 - x) BNT-xBCN samples with x = 0.0475 suggested that the present materials have a modulation structure arranged by a double period along the [111] direction. It is shown that the tetragonal BNT-BCN (x = 0.0475) solid solution with a composition of 0.9490BNT center dot 0.0473BCN center dot 0.0037MnO(2) near the MPB has a piezoelectric coefficient (d(33)), a relative permittivity (epsilon(T)(33)/epsilon(0)), and a remanent polarization (P-r) of approximately 1.8, 3.2, and 2.8 times larger, respectively, than those of the BNT solid solution without BCN substitution. (C) 2011 The Japan Society of Applied Physics

A fast-proton-conducting porous tubular glass electrolyte was prepared by surface modification of glass, and the direct methanol fuel cell performance of the glass electrolyte was measured. The glass electrolyte showed very low methanol permeability of 2.1 x 10(-7) cm(2)s(-1) compared with the polymer electrolyte Nafion (R) (2.3 x 10(-6) cm(2) s(-1)). An open-circuit voltage of approximately 0.7 V was obtained at room temperature, which corresponds to 15 V when the tubes are stacked in a 6.5 cm(3) portable cell.

Electronic as well as ionic conducting properties for oxyapatite-type solid electrolytes based on lanthanum silicate, La(9.333) (+) (x)Si(6)O(26 + 1.5x) (LSO) were investigated in the oxygen-excess region (x &gt; ca. 0.3). We have found that the oxygen excess-type LSO (OE-LSO), namely La(10)Si(6)O(27) on weighted basis, exhibited high conductivity, and substitution of the Si-site of LSO with some dopants (M(n+)) had a positive effect toward the conducting property. Furthermore, it was also found that addition of a very small amount of iron ions into the M-doped OE-LSO, La(10)(Si(6-y)M(y)(n+))O(27-(2-0.5n)y), improved its conductivity. On the other hand, replacement of the La-site with various ions for La(10)(Si(6-y)M(y)(n+))O(27-(2-0.5n)y) did little to improve conductivity. The electronic transport numbers for Al-doped OE-LSO with Fe-addition, (1-alpha)(La(10)(Si(5.8)Al(0.2))O(26.9))-alpha(FeO(gamma)), evaluated with the Hebb-Wagner polarization method were very low: i.e., 1.1 x 10(-3) and 2.9 x 10(-3) under P(O(2))=1.1 x 10(4) Pa at 1073 K for alpha = 0.00 and 0.005, respectively. Conductivity for each sample was unchanged under humidified atmosphere at 1073 K sustained for over 50 h, revealing that both compositions were chemically stable. It was concluded that 0.995{La(10)(Si(5.8)Al(0.2))O(26.9)}-0.005(FeO(gamma)) is suitable for the fuel cell electrolytes because of its high and almost pure ionic conductivity, and its good chemical stability under humidified as well as reducing conditions. (C) 2010 Elsevier B.V. All rights reserved.

Phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) coatings [xPhTES center dot(100 - x)TEOS (mol%)] (x = 0 - 80) were prepared on polycarbonate (PC) substrate, and adhesion, surface hardness and distribution of phenyl groups were studied. The coatings with more than 60 mol% of PhTES showed good adhesion (a parts per thousand 100%), and the pencil hardness of PC substrate (4B) improved to 2B or B after the coatings. Bulk gels with the same compositions were also prepared, and distribution of phenyl groups were estimated using fourier transform infrared (FT-IR) spectroscopy (KBr method for bulk gels and attenuated total reflection (ATR) method for coatings). A significant difference for the distribution of phenyl groups was clearly observed between bulk gels and coatings, suggesting PC substrate affects the distribution of phenyl groups in coatings. The adhesion and FTIR results revealed that there is an interaction caused by pi-electrons between benzene rings on PC substrate and phenyl groups of PhTES-TEOS coatings. It was found that the adhesion was strongly correlated with the phenylsilsesquioxane networks formed around PC substrate side.

Na2O-B2O3-SiO2 and Na2O-P2O5-SiO2 glasses show a spinodal phase separation to SiO2 rich and Na2O center dot B2O3 or Na2O center dot P2O5 rich phases by heating. Herein we report for the first time the application of phosphosilicate glasses to fuel cells operated at moderate temperature. The glass was prepared by conventional melting method. The mixed-alkali glass showed 100% proton transport at 400-500 degrees C. Two crucial aspects, the first is the enhancement of proton transport number by mixing two types of alkali metal oxides, and the second is proton infiltration into the glass under hydrogen (fuel cell) atmosphere, are reported. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3574527] All rights reserved.

Influences on electrical property and phase relationship of oxyapatite-type solid electrolytes based on lanthanum silicate (LSO) were investigated by addition of a small amount of transition metal elements. It was revealed that a very small amount of 3d-transition metal additives into the La-excess-type, i.e., oxygen-excess-type Al-doped LSO, La(10)(Si(5.8)Al(0.2))O(26.9), changed its electrical conductivity. Some metals such as iron and chromium showed a positive effect for an increase in conductivity. The specimen with a nominal composition of 0.995{La(10)(Si(5.8)Al(0.2))O(26.9)}-0.005(FeO(gamma)), showed the maximum electrical conductivity among the specimens measured in this study. Formed phases of oxygen-excess-type Al-doped LSO based materials were found to be altered even by addition of a small amount of transition metal oxides. La-rich impurity phases such as La(OH)(3) and La(2)SiO(5) are usually detected in the oxygen-excess-type LSO, whereas no formation of La-rich impurity phases was confirmed in the case of iron addition. These results suggest that the enhancement of electrical conductivity by iron addition is due to a disappearance of the La-rich impurity phases as insulators and/or an increase in the concentration of oxygen interstitial carriers within the LSO phase. (C) 2010 Elsevier B.V. All rights reserved.

Porous glasses with the surface area of approximate to 300 m(2)/g were prepared utilizing the spinodal-type phase separation of Al2O3-doped Na2O-B2O3-SiO2 glasses. The proton conductivity under humidified conditions and their relations to the amount of doped Al2O3 were investigated. The proton conductivity of the glass doped with 2 mol % of Al2O3 was about 6 times higher than that of the undoped glass. Fourier transform infrared (FT-IR) measurements revealed that the absorption by the strongly hydrogen-bonded OH groups increased with increasing the amount of Al2O3. Bond overlap populations (BOPs), which are directly related to the strength of the covalent bond, between the surface OH groups and an absorbed water molecule were calculated based on a first-principles theory (DVX alpha). The BOP values between O and H of the surface OH groups decreased by the Al2O3 doping. Substitution of Si atoms of the Si-O-Si silica networks with Al atoms, and formation of the Al-OH-Si bonds effectively improved the proton conductivity under humidified conditions. (C) 2010 The Ceramic Society of Japan. All rights reserved.

c-axis-oriented epitaxial 1.2-mu m PbMg0.047Nb0.095Zr0.416Ti0.442O3 (PMNZT) films with a comparatively large piezoelectric coefficient d(33) (=90 pC/N) fabricated on Pt(100)/MgO(100) substrates by metalorganic decomposition were treated by hot isostatic pressing (HIP). The HIP-pressure dependence on d(33) of the 1.2-mu m PMNZT samples treated at 850 degrees C for 1 h under Ar/O-2 mixed gas pressures of 49-196 MPa was investigated. The d(33) value of the HIP-treated samples was almost constant (=60 pC/N), independently of the amplitude in pressure. Although the HIP treatment hardly contributes to an improvement on d(33), it can be expected to minimize the deviation of d(33) and provide highly-reliable piezoelectric elements.

Highly dense pellets of an oxygen excess-type lanthanum silicate (La(9.333+x)Si(6)O(26+1.5x), x &gt; ca. 0.3, OE-LSO) were successfully fabricated, and their electrical conducting properties were studied. The replacement of Si by Al enhanced its conductivity, and the slightly Al-doped OE-LSO specimen [La(9.62)(Si(5.79)Al(0.21))O(26.33)] had excellent features as a solid electrolyte; that is, it had high ionic conductivity and was highly stable under reducing as well as oxidizing conditions at 873-1073 K. In addition, the ionic transference number was higher than 0.99. In the fuel cell utilizing this electrolyte (0.72 mm thick), (La(0.6)Sr(0.4))(Co(0.2)Fe(0.8))O(3-delta) cathode, and Ni-Ce(0.9)Gd(0.1)O(1.95-delta) anode, good performance with the maximum power density of ca. 0.25 W cm(-2) was obtained at 1073 K. In addition, this electrolyte also had high compatibility with these conventional mixed conducting electrodes, according to an analysis near the electrode/electrolyte interfaces after the fuel cell test. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3464803] All rights reserved.