内田 寛

(Bi,K)TiO<inf>3</inf>films were grown on (001)<inf>c</inf>SrRuO<inf>3</inf>// (100)SrTiO<inf>3</inf>substrates by pulsed laser deposition (PLD) at various temperatures. The K/Ti and Bi/Ti ratios of the films were almost the same at 350 and 500 °C, but decreased markedly at 650 °C. The ferroelectric property was ascertained for epitaxial tetragonal (Bi,K)TiO<inf>3</inf>films grown at 500 °C from polarization–electric field relationships, and their saturation polarization (P<inf>sat</inf>) and coercive field (E<inf>c</inf>) at a maximum electric field of 800 kV/cm were 18 µC/cm²and 300 kV/cm, respectively. To improve the ferroelectric property, the films were heat-treated at 650 °C while keeping the films in the PLD chamber after film deposition. These films also maintained a (001)-oriented epitaxy and had a tetragonal symmetry. The P<inf>sat</inf>and E<inf>c</inf>obtained at an electric field of 800 kV/cm were changed to 22 µC/cm²and 95 kV/cm, respectively. Moreover, these P<inf>sat</inf>and E<inf>c</inf>values increased to 31 µC/cm²and 165 kV/cm, respectively, at a maximum electric field of 1500 kV/cm. These heat-treated (Bi,K)TiO<inf>3</inf>films showed piezoelectricity with an apparent piezoelectric coefficient (d<inf>33(AFM)</inf>) of 22 pm/V.

0.07YO(1.5)-0.93HfO(2) (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt.% Sn-doped In2O3(ITO)//(111) yttria-stabilized zirconia, (111) Pt/TiOx/SiO2/(001)Si substrates, and (111) ITO/(111) Pt/TiOx/SiO2/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including theta-2 theta measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111) ITO//(111) yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111) ITO/(111) Pt/TiOx/SiO2/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111) Pt/TiOx/SiO2/(001)Si substrate, which does not contain ITO. Polarization-hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (P-r) of 9.6 and 10.8 mu C/cm(2) and coercive fields (E-c) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature. Published by AIP Publishing.

Thin films of the BaTiO3-Bi(Mg1/2Ti1/2) O-3 (BT-BMT) solid-solution system with preferential crystal orientation of (100) and (111) plane were fabricated on (100) SrRuO3//(100) SrTiO3 and (111) SrRuO3//(111) SrTiO3 substrates by CSD technique. Enhanced dielectric permittivity (epsilon(r)) of approximately 800 was confirmed for the (111)-oriented BT-BMT film at room temperature, which is significantly larger than those of (100)-or randomly-oriented films. The BT-BMT films exhibited relatively stable temperature coefficient of capacitance (TCC) independent of their crystal orientation, that allows enhanced epsilon(r) up to 400 degrees C without drastic change of the capacitance. These properties can be favorable for the application of dielectric capacitors in hightemperature electronics. (C) 2016 The Ceramic Society of Japan. All rights reserved.

The constituent phases, electrical conductivity, and Seebeck coefficient of Ca-Si films deposited on (001) Al2O3 substrates by a radio frequency magnetron sputtering method using a Mg disk target with Ca and Si chips are investigated. X-ray diffraction analysis indicates that the films consist of a single phase of CaSi2, CaSi or Ca5Si3 that are deposited together with the films consisting of a mixture of CaSi2 and CaSi. Films with a CaSi2 or CaSi single phase exhibit a metallic behavior. In contrast, films with a Ca5Si3 single phase show p-type conduction and their Seebeck coefficient reaches 90 mu V/K at 400A degrees C.

To investigate the impact of mechanical stress on their ferroelectric properties, polycrystalline (Hf0.5Zr0.5)O-2 thin films were deposited on (111)Pt-coated SiO2, Si, and CaF2 substrates with thermal expansion coefficients of 0.47, 4.5, and 22 x 10(-6)/degrees C, respectively. In-plane X-ray diffraction measurements revealed that the (Hf0.5Zr0.5)O-2 thin films deposited on SiO2 and Si substrates were under in-plane tensile strain and that their volume fraction of monoclinic phase decreased as this strain increased. In contrast, films deposited on CaF2 substrates were under in-plane compressive strain, and their volume fraction of monoclinic phase was the largest among the three kinds of substrates. The maximum remanent polarization of 9.3 mu C/cm(2) was observed for Pt/(Hf0.5Zr0.5)O-2/Pt/TiO2/SiO2, while ferroelectricity was barely observable for Pt/(Hf0.5Zr0.5)O-2/Pt/TiO2/SiO2/CaF2. This result suggests that the in-plane tensile strain effectively enhanced the ferroelectricity of the (Hf0.5Zr0.5)O-2 thin films. Published by AIP Publishing.

This brief article reports a suitable preparation of TiO2 hollow particles using titanium tetra-isopropoxide (TTIP) as a precursor and highly dispersed calcium carbonate (CaCO3) particle templates prepared from CaCl2 and dimethylcarbonate in the presence of the dispersing agent polyvinylpyrrolidone. The synthesis of TiO2 hollow particles was optimized considering certain experimental conditions: (a) the amount of TTIP, (b) the hydrolysis rate of TTIP in water/ethanol solvent, and (c) the mass of CaCO3 template particulates. The morphology and particle sizes of the resulting hollow particles (CaCO3 templates removed on addition of acid) were assessed by scanning electron microscopy (SEM and SEM-EDX); their crystalline phase (anatase) was determined by X-ray diffraction techniques and the specific surface area by the BET method. A formation mechanism of the TiO2 particles is described in terms of the TiO2 particulates generated under each experimental condition. The photoactivity of the TiO2 hollow particles was subsequently examined through the transformation of a volatile organic pollutant (iso-propanol) in air whose faster rate of photodegradation relative to TiO2 particles (synthesized without CaCO3) correlates with the greater specific surface area of these hollow particles (19.0 vs. 65.1 m(2) g(-1)). [GRAPHICS]

Orientation control of {100}-oriented epitaxial orthorhombic 0.07YO(1.5)-0.93HfO(2) films grown by pulsed laser deposition was investigated. To achieve in-plane lattice matching, indium tin oxide (ITO) and yttria-stabilized zirconia (YSZ) were selected as underlying layers. We obtained (100)-and (001)/(010)-oriented films on ITO and YSZ, respectively. Ferroelastic domain formation was confirmed for both films by X-ray diffraction using the superlattice diffraction that appeared only for the orthorhombic symmetry. The formation of ferroelastic domains is believed to be induced by the tetragonal-orthorhombic phase transition upon cooling the films after deposition. The present results demonstrate that the orientation of HfO2-based ferroelectric films can be controlled in the same manner as that of ferroelectric films composed of conventional perovskite-type material such as Pb(Zr, Ti)O-3 and BiFeO3. (C) 2016 AIP Publishing LLC.

(KxNa1-x)NbO3 films were deposited on Nb-doped (100)SrTiO3 substrates at 240 degrees C for times between 1 and 6 h by a hydrothermal method. Over this time series, the measured (K + Na)/Nb ratio of the films was found to remain constant, but the bulk K/(K + Na) ratio, x, decreased from an initial value of 0.75-0.56. It was determined that film growth initially proceeded through crystallization of the K-rich phase (K0.75Na0.25)NbO3. For film growth times greater than 3 h, a second perovskite phase with a smaller unit cell volume was detected, with an estimated composition of (K0.36Na0.64)NbO3. As such, the measured bulk composition value x = 0.56 was determined to be the result of a combination of these two phases, as opposed to originating from a single phase. Cross-sectional transmission electron microscopy analyses of films prepared for 6 h revealed that they consist of two layers in the direction normal to the substrate; this bilayer-type structure, only observed for hydrothermal growth of this material, is considered to arise from the large solubility mismatch between the Nb precursor and KOH and NaOH in the growth solution.

A proton-conductive BaCe0.9Y0.1O3-δ (BCYO) thin-film, one of the candidates for the electrolyte of intermediate-temperature solid oxide fuel cells (IT-SOFCs), was deposited on (111)Pt/TiO2/SiO2/(100)Si substrate by the RF magnetron sputtering method. The sputtering conditions, i.e., deposition temperature, pressure, and sputtering gases, were examined to improve the crystallinity of the films. The BCYO films deposited at more than 500 °C were well crystallized and showed only 110 diffraction. The addition of O2 into the sputtering gas causes adverse results of lower crystallinity and lower deposition rates. A wide-range XRD reciprocal space mapping also revealed that the (110)-oriented BCYO films can be obtained on (111)Pt/TiO2/SiO2/(100)Si substrates without the need to use any buffer layers. We consider that this BCYO film possibly shows high proton conductivity and may be a suitable material for the SOFC electrolyte because of its high crystallinity.

To realize a high-temperature capacitor, uniaxially (001)-oriented CaBi4Ti4O15 films with various film thicknesses were prepared on (100)(c)SrRuO3/Ca2Nb3O10- nanosheet/glass substrates. As the film thickness decreases to 50 nm, the out-of-plane lattice parameters decrease while the in-plane lattice ones increase due to the in-plane tensile strain. However, the relative dielectric constant (epsilon(r)) at room temperature exhibits a negligible degradation as the film thickness decreases to 50 nm, suggesting that epsilon(r) of (001)-oriented CaBi4Ti4O15 is less sensitive to the residual strain. The capacitance density increases monotonously with decreasing film thickness, reaching a value of 4.5 mu F/cm(2) for a 50-nm-thick nanofilm, and is stable against temperature changes from room temperature to 400 degrees C irrespective of film thickness. This behaviour differs from that of the widely investigated perovskite-structured dielectrics. These results show that (001)-oriented CaBi4Ti4O15 films derived using Ca2Nb3O10- nanosheets as seed layers can be made candidates for high-temperature capacitor applications by a small change in the dielectric properties against film thickness and temperature variations.

Supercritical fluid deposition (SCFD) of SiO2-based films was proposed using TEOS precursor with oxidizing agents, for the purpose of low-temperature film deposition. The film deposition was performed in a batch-type closed chamber filled with supercritical carbon dioxide (CO2) fluid. The SiO2-based films were deposited on aluminum electrodes coated on silicon wafers (Al/Si) at the substrate temperature above 150 degrees C. Oxidizing agents such as O-2 gas and aqueous H2O2 solution promoted the removal of C2H5OH byproduct and the formation of strong Si-O network, whereas it also promoted the homogeneous nucleation of granular precipitation and the H2O adsorption in/on the resulting films. The processing temperature of the SCFD was significantly lower than those by thermal CVD and comparable or higher than those by plasma-enhanced CVD, although the resulting films obtained exhibited relatively large dielectric loss which depends on the presence of C2H5OH and H2O byproducts. (C) 2016 The Ceramic Society of Japan. All rights reserved.

The temperature dependence of the capacitance of (111)(c)-oriented (0.90-x)BaTiO3-0.10Bi(Mg0.5Ti0.5)O-3-xBiFeO(3) solid solution films is investigated. These films are prepared on (111)(c)SrRuO3/(111)Pt/TiO2/SiO2/(100)Si substrates by the chemical solution deposition technique. All the films have perovskite structures and the crystal symmetry at room temperature varies with increasing x ratio, from pseudocubic when x = 0-0.30 to rhombohedral when x = 0.50-0.90. The pseudocubic phase shows a high relative dielectric constant (epsilon(r)) (ranging between 400 and 560 at room temperature and an operating frequency of 100 kHz) and a low temperature dependence of capacitance up to 400 degrees C, while maintaining a dielectric loss (tan delta) value of less than 0.2 at 100 kHz. In contrast, epsilon(r) for the rhombohedral phase increases monotonically with increasing temperature up to 250 degrees C, and increasingly high tan delta values are recorded at higher temperatures. These results indicate that pseudocubic (0.90-x)BaTiO3-0.10Bi(Mg0.5Ti0.5)O-3-xBiFeO(3) solid solution films with (111) orientation are suitable candidates for high-temperature capacitor applications. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

To date syntheses of nitrogen-doped TiO2 photocatalysts (TiO2-xNx) have been carried out under high temperatures and high pressures with either NH3 or urea as the nitrogen sources. This article reports for the first time the facile preparation of N-doped TiO2 (P25 titania) in aqueous media at ambient temperature and pressure under inert conditions (Ar- and N-2-purged dispersions) with 4-nitrophenol (or 4-nitro-benzaldehyde) as the nitrogen source. The resulting N-doped P25 TiO2 materials were characterized by UV/Vis and X-ray photoelectron spectroscopies (XPS) that confirmed the presence of nitrogen within the photocatalyst; X-ray diffraction (XRD) techniques confirmed the crystalline phases of the doped material. The photocatalytic activity of N-doped TiO2 was assessed through examining the photodegradation of 4-chlorophenol in aqueous media and iso-propanol as a volatile pollutant under UV/Vis and visible-light irradiation. Under visible light irradiation, undoped P25 was inactive contrary to N-doped P25 that successfully degraded 95% of the 4-chlorophenol (after 10 h) and 23% of iso-propanol (after 2.5 h).

Energy-harvesting properties were investigated for the flexible piezoelectric devices, Pt/hydrothermally synthesized (K0.88Na0.12)NbO3/SrRuO3/metal foil, fabricated at low process temperatures below 300 degrees C. Fabricated devices had high flexibility, and cracking and peeling were not observed under the bending condition with the maximum curvature of 5.2mm. The estimated Young's modulus of the fabricated flexible devices was 37GPa. The pulse poling treatment with AC voltage above 150 V enhanced the energy-harvesting properties. Although the dielectric constant was almost unchanged (epsilon(r) = 120 at 200 Hz), the maximum output voltage measured at an acceleration of 10m/s(2) was observed at a resonance frequency of 126 Hz, and this voltage increased from 7.2 to 11 V after pulse poling treatment at 200V. The maximum output power was 7.7 mu W at a load resistance of 560 k Omega. The calculated Q and K-2 values were 30 and 0.0014, respectively. The power density was 1.8 mu W/(G(2).mm(3)), which is higher than the previous reports for films and sintered bodies of (KxNa1-x) fabricated above 500 degrees C. (C) 2015 The Japan Society of Applied Physics

A new orientation control method for depositing (110)-oriented perovskite thin films was demonstrated using a (101)PdO//(111)Pd buffer layer on (100) Si substrates, which is widely used in integrated ferroelectric and dielectric applications. The (101)-oriented PdO was obtained by oxidizing (111) Pd films deposited on a (111)Pt/TiOx/SiO2/(100)Si substrate and (110)-oriented perovskites including SrRuO3 and (Ba-0.5,Sr-0.5)TiO3 (BST) were obtained on (101)PdO by the RF magnetron sputtering method. Although the BST films deposited at 500 degrees C were not crystallized, the BST films deposited above 600 degrees C are fully crystallized and the (110)-orientation is dominant. The (110)-oriented BST thin film showed good dielectric property with high dielectric constant (&gt;600) at 0 kV/cm and high tunability (&gt;50% at +/- 200 kV/cm). Comparing this dielectric property with those of other oriented BST films, both the dielectric constant and the tunability tend to decrease in the order of (111)-, (100)-, and (110)-preferred orientations. (C) 2015 The Japan Society of Applied Physics

(100)- and (111)-oriented epitaxial Pb(Mg1/3Nb2/3)O3 films with 500 and 1300 nm in thickness were grown by metal organic chemical vapor deposition. Remained strain was almost relaxed because the crystal structure of the films was almost the same as that of bulk Pb(Mg1/3Nb2/3)O3. Relative dielectric constant showed the maximum value against the temperature that depended on the measurement frequency. Maximum relative dielectric constant, εr(max.), and the temperature showing εr(max.), T(max.), decreased and increased with the frequency, respectively, are in good agreement with reported data for the bulk. εr(max.) and T(max.), respectively increased and decreased with the film thickness and (111)-oriented films showed larger value than that of the (100)-oriented one. Ferroelectricity was observed for all films up to 297 K and monotonously decreased with increasing temperature. Saturation polarization value increased with the film thickness and (111)-oriented films showed larger value than (100)-oriented ones. On the other hand, the coercive field decreased with increasing film thickness, but was almost independent with the film orientation.

Lead zirconate titanate (PZT) film with polar axis orientation was grown on a SUS 316L stainless steel substrate with the help of a Ca2Nb3O10 nanosheet (ns-CN) layer that had a pseudo-perovskite-type crystal structure. The ns-CN buffer layer was supported on a platinized SUS 316L (Pt/SUS) substrate, followed by chemical solution deposition (CSD) of the PZT films with tetragonal symmetry (Zr/Ti = 40/60). The PZT films consisting of c-domain, with [001]-axis orientation of the perovskite unit cell, were deposited on the ns-CN/Pt/SUS substrate owing to (i) epitaxial lattice matching between the unit cell of PZT and substrate surface and (ii) in-plane thermal stress applied to the PZT film during cooling-down step of CSD procedure. The c-domain-oriented PZT film on ns-CN/Pt/SUS substrate exhibited enhanced remanent polarization of approximately 52 mu C/cm(2) and lowered dielectric permittivity of approximately 230, which are superior to those of conventional PZT films with random crystal orientation and comparable to those of epitaxial PZT films grown on (100) SrRuO3//(100)SrTiO3 substrates. (C) 2015 Author(s).

One-axis-oriented BiFeO3 (BFO)-based films were fabricated on platinized silicon and SUS 316L substrates using nanosheets of calcium niobate (ns-CN) with pseudo-perovskite crystal structure. Ca2Nb3O10 nanosheets (ns-CNs) were supported on the substrates by dip coating, followed by chemical solution deposition (CSD) of Mn-doped BFO (Mn-BFO) films. Preferential crystal growth of (100)-oriented BFO films was achieved on both ns-CN/(111)Pt/TiO2/(100)Si and ns-CN/(111)Pt/SUS316L substrates. The out-of-plane lattice parameters of the BFO films on ns-CN/(111)Pt/SUS316L were larger than the parameter reported for BFO bulk because of elastic deformation caused by thermal stress between the BFO films and SUS316L substrate, whereas those of the films on ns-CN/(111) Pt/TiO2/(100) Si were smaller than the reported value. The remanent polarization of the Mn-BFO films was enhanced to approximately 60 mu C/cm(2) on ns-CN/(111)Pt/SUS316L because of the compressive thermal stress that causes elastic elongation of Mn-BFO crystals to align or change the tilt angle of their polar axes for the substrate surface. (C) 2015 The Ceramic Society of Japan. All rights reserved.

Oxygen vacancies in zinc oxide (ZnO) are intrinsic defects, which are easily generated during crystal growth or device processing. Investigations of defects, such as oxygen vacancies, are important to understand the properties of ZnO. In this study, we attempt to quantify oxygen vacancies in ZnO powders using Raman spectroscopy. ZnO powder is reduced in a hydrogen atmosphere at 300-600 degrees C for 30-90 min. The peak position of the E-2(high) mode, which is related to the oxide ion vibration, shifts toward a lower frequency as the oxygen vacancies increase. Upon re-oxidation, the initial E-2(high) peak position is restored. Because the E-2(high) peak shift is scaled with the amount of oxygen vacancies, this relationship can be used to estimate the amount of oxygen vacancies.

Lead- and alkali-metal-free BaTiO<inf>3</inf>–Bi(Mg<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf>–BiFeO<inf>3</inf>solid-solution thin films were prepared on (111)<inf>c</inf>SrRuO<inf>3</inf>/(111)Pt/TiO<inf>2</inf>/SiO<inf>2</inf>/(100)Si substrates by chemical solution deposition (CSD) and their crystal structure and dielectric properties were investigated. The lattice spacing as a function of z/(x + z) in xBaTiO<inf>3</inf>–0.1Bi(Mg<inf>0.5</inf>Ti<inf>0.5</inf>)O<inf>3</inf>–zBiFeO<inf>3</inf>indicated the existence of phase boundaries (pseudocubic/rhombohedral) in the range of z/(x + z) = 0.33–0.56, where the relatively high relative dielectric constant, ε<inf>r</inf>, of above 800 was obtained. On the other hand, dielectric loss, tan δ, of below 0.2 was confirmed in the range z/(x + z) = 0–0.87, which rapidly increased toward z/(x + z) = 1.0. The relatively high ε<inf>r</inf>values of these films deposited on Si substrates by a solution-based process suggest that they can be used as alternative to Pb(Zr,Ti)O<inf>3</inf>, KNbO<inf>3</inf>, and (Bi<inf>1/2</inf>Na<inf>1/2</inf>)TiO<inf>3</inf>-based films.

Thin films of the BaTiO<inf>3</inf>–Bi(Mg<inf>1/2</inf>Ti<inf>1/2</inf>)O<inf>3</inf>(BT–BMT) solid-solution system were fabricated with the aim of achieving a stable temperature coefficient of capacitance (TCC) favorable for high-temperature electronics. A single perovskite phase with pseudocubic symmetry was obtained for the films fabricated by chemical solution deposition on (111)Pt/TiO<inf>2</inf>/(100)Si substrates in the composition range of x = 0–0.80 for (1 − x)BT–xBMT. BMT added to the BaTiO<inf>3</inf>-based films enhanced the crystallinity of the perovskite phase and resulted in saturated P–E hysteresis behavior with remanent polarization of up to 13 µC/cm². BMT addition led to gradual dielectric relaxation, which also resulted in stable TCC behavior with a relative dielectric constant of approximately 400 in the temperature range of RT − 400 °C, especially for the BT–BMT films with x = 0.20–0.40.

Thin films of the BaTiO3-Bi(Mg1/2Ti1/2)O-3 (BT-BMT) solid-solution system were fabricated with the aim of achieving a stable temperature coefficient of capacitance (TCC) favorable for high-temperature electronics. A single perovskite phase with pseudocubic symmetry was obtained for the films fabricated by chemical solution deposition on (111)Pt/TiO2/(100)Si substrates in the composition range of x = 0-0.80 for (1 - x)BT-xBMT. BMT added to the BaTiO3-based films enhanced the crystallinity of the perovskite phase and resulted in saturated P-E hysteresis behavior with remanent polarization of up to 13 mu C/cm(2). BMT addition led to gradual dielectric relaxation, which also resulted in stable TCC behavior with a relative dielectric constant of approximately 400 in the temperature range of RT - 400 degrees C, especially for the BT-BMT films with x = 0.20-0.40. (C) 2014 The Japan Society of Applied Physics

KNbO3 films were synthesized at 120-240 degrees C by a hydrothermal method. The deposition amount of KNbO3 films decreased with decreasing deposition temperature because the deposition rate decreased together with the increase in the starting time of precipitation. The KNbO3 phase was ascertained at temperature as low as 120 degrees C in films deposited on (100)(c)SrRuO3//(100)SrTiO3 substrates. On the other hand, powders prepared at 150 degrees C included the Nb2O5 phase as well as the KNbO3 phase. In addition, powders prepared at 120 degrees C consist of the K3Nb7O19 phase instead of the KNbO3 phase. KNbO3 films were deposited at 150 degrees C on LaNiO3/Pt/Ti/polysulfone substrates. Films consisting of the polycrystalline KNbO3 phase were obtained, and their ferroelectricity and piezoelectricity were observed. The remanent polarization and piezoelectric coefficient were 4.2 mu C/cm(2) and 20-32 pm/V, respectively. (C) 2014 The Japan Society of Applied Physics

Lead- and alkali-metal-free BaTiO3-Bi(Mg0.5Ti0.5)O-3-BiFeO3 solid-solution thin films were prepared on (111)(c)SrRuO3/(111)Pt/TiO2/SiO2/(100)Si substrates by chemical solution deposition (CSD) and their crystal structure and dielectric properties were investigated. The lattice spacing as a function of z/(x + z) in xBaTiO(3)-0.1Bi(Mg0.5Ti0.5)O-3-Bi(Mg0.5Ti0.5)O-3-zBiFeO(3) indicated the existence of phase boundaries (pseudocubic/rhombohedral) in the range of z/(x + z). 0.33-0.56, where the relatively high relative dielectric constant, Er, of above 800 was obtained. On the other hand, dielectric loss, tan delta, of below 0.2 was confirmed in the range z/(x + z) = 0-0.87, which rapidly increased toward z/(x+ z) = 1.0. The relatively high epsilon(r) values of these films deposited on Si substrates by a solution-based process suggest that they can be used as alternative to Pb(Zr,Ti)O-3, KNbO3, and (Bi1/2Na1/2)TiO3-based films. (C) 2014 The Japan Society of Applied Physics

We proposed a thin-film capacitor with a stable temperature coefficient of capacitance (TCC) based on bismuth layer-structured dielectrics, CaBi4Ti4O15. Two types of doping were conducted to lower the dielectric loss in a higher temperature range above 300 degrees C, i.e., Mn ion to compensate for lattice defects in crystalline grains and Bi12SiO20 to form a grain boundary phase were attempted in order to improve the insulating property of the oriented CaBi4Ti4O15 films. (001) one-axis oriented Mn-doped or Bi12SiO20-doped CaBi4Ti4O15 films (with Mn or Bi12SiO20 content up to 3.0 or 1.75%) were fabricated successfully on (111) Pt/TiO2/(100) Si substrates buffered by (001) Ca2Nb3O10 nanosheets. These films exhibited a relatively lower loss factor in the temperature range from R.T. up to 400 degrees C. In particular, the behavior of TCC on the Bi12SiO20-doped CaBi4Ti4O15 film was significantly stable, with a change in capacitance, Delta C/C-R. T., within 10% even at 400 degrees C. (C) 2014 The Ceramic Society of Japan. All rights reserved.

Magnesium silicide (Mg2Si) thick films with (110) orientation were fabricated on (001) sapphire substrate using radiofrequency magnetron sputtering. Stoichiometric Mg2Si films with composition Si/(Mg + Si) = 0.33 were achieved over a range of vacuum from 10 mTorr to 140 mTorr and 300A degrees C. On postannealing the film at 500A degrees C, the out-of-plane lattice parameter shifted to lower values and the electrical conductivity increased by two orders of magnitude. A room-temperature Seebeck coefficient of 517 mu V K-1 was observed and found to decrease with increasing temperature; the Seebeck coefficient remained at a constant positive value of 212 mu V K-1 at 500A degrees C. This can be related to the possibility of p-type conduction in this temperature range.

One-axis-oriented Pb(Zr,Ti)O-3 (PZT) films were fabricated using a chemical solution deposition technique on (111)Pt/TiO2/(100)Si and Incone1625 substrates buffered by nanosheet Ca2Nb3O10 (ns-CN). The (001)-oriented PZT crystals (Zr/Ti=0.40:0.60, tetragonal) were preferentially grown on (001)ns-CN/Incone1625, whereas the PZT crystals deposited on (001)ns-CN/(111)Pt/ TiO2/(100)Si exhibited preferential PZT(100) orientation. The resulting PZT film on (001)ns-CN/Incone1625 indicated remanent polarization of approximately 59 mu C/cm(2), which was significantly larger than that on (001)ns-CN/(111)Pt/TiO2/(100)Si.

Nanosheet Ca2Nb3O20 (ns-CN) layers with pseudo-perovskite-type crystal configuration were applied on the surface of polycrystalline metal substrates to achieve preferential crystal orientation of Pb(Zr,Ti)O-3 (PZT) films for the purpose of enhanced ferroelectricity comparable to that of epitaxial thin films. PZT films with tetragonal symmetry (Zr/Ti= 0.40 : 0.60) were fabricated by chemical solution deposition (CSD) on ns-CN-buffered Inconel 625 and SUS 316L substrates, while ns-CN was applied on the the substrates by dip-coating. The preferential crystal growth on the ns-CN layer can be achieved by favorable lattice matching between (001)/(100) PZT and (001)ns-CN planes. The degree of (001) orientation was increased for PZT films on ns-CN/Inconel 625 and ns-CN/SUS 316L substrates, whereas randomly-oriented PZT films with a lower degree of (001) orientation were grown on bare and Inconel 625 films. Enhanced remanent polarization of 60 mu C/cm(2) was confirmed for the PZT films on ns-CN/metal substrates, ascribed to the preferential alignment of the polar [001] axis normal to the substrate surface, although it also suffered from higher coercive field above 500 kV/cm caused by PZT/metal interfacial reaction. (c) 2013 The Japan Society of Applied Physics

Epitaxial (KxNa1-x)NbO3 films with various compositions x were deposited on Nb-doped (100)SrTiO3 single crystal substrates at 240 degrees C by the hydrothermal method. Detailed crystal structures were analyzed by X-ray diffraction. All the (KxNa1-x)NbO3 films consisted of a perovskite phase without any impurity phase. High-temperature XRD data showed that (KxNa1-x)NbO3 films with x = 0.03 and 0.86 transformed to a single cubic phase at 600 degrees C through the intermediate phase. On the other hand, (KxNa1-x)NbO3 films with x = 0.24 showed two diffraction peaks at 600 degrees C originating from individual phases having different unit cell volumes. The result shows that these films consisted of a mixture of two perovskite phases with K-and Na-rich(KxNa1-x)NbO3 composition. (C) 2013 The Japan Society of Applied Physics

Epitaxial films of tetragonal (001)/(100)-oriented (2/3)Bi(Zn 1/2Ti1/2)O3-(1/3)BiFeO3 were grown on (100)cSrRuO3//(100)SrTiO3 substrates by metalorganic chemical vapor deposition. 93% of the film is occupied by c-domain [(001) orientation], and the out-of-plane (c-axis) and in-plane (a-axis) lattice parameters are 0.465 nm and 0.381 nm, respectively. The tetragonal distortion, (c/a)-1, is 22% which is 3.5 times larger than that of PbTiO3 (6.3%). High-angle annular dark-field-scanning transmission electron microscopy images show clear c-/a-domain structures with unusual boundary angles of 51°/39°due to the large c/a ratio of tetragonal phase. High temperature X-ray diffraction measurements reveal that the Curie temperature of this film is above 800°C. © 2013 AIP Publishing LLC.

The occupation sites of Dy- or Y-substituted PZT films were identified using Raman spectroscopy, and the correlation between the occupation site and ferroelectric property was investigated. When Dy or Y was less than 2%, the ferroelectric properties improved because substitution occurred at the B-sites of the PZT films. However, the ferroelectric properties decreased when the substituted ions exceeded 4% because substitution occurred at both B- and A-sites. Consequently, it is important to accurately introduce substituted ions into the B-sites in a PZT film to improve the ferroelectric properties. Copyright © Taylor &amp; Francis Group, LLC.

(K0.88Na0.12)NbO3 (KNN) thick films with various thicknesses were prepared on Ni-based metal substrates by hydrothermal method. Although the deposition of KNN films was hardly observed directly on metal substrates until 12 h, the amount of KNN films deposited on both SrRuO3/LaNiO3- and SrRuO3-covered Ni based metal substrates increased to about 5 A mu m with increasing deposition time above 3 h. X-ray diffraction studies confirmed the formation of {100} (c) - and randomly-oriented KNN films on SrRuO3/LaNiO3- and SrRuO3-covered metal substrates, respectively. Ferroelecctric property studies revealed an improved remanent polarization and an improved piezoelectric response of {100} (c) -oriented KNN films over the randomly-oriented KNN films. In addition, the values for {100} (c) -oriented KNN films were similar to those of {100} (c) -oriented epitaxial KNN films prepared on (100) (c) SrRuO3//SrTiO3 substrates.

SrBi4Ti4O15 (SBTi) and CaBi 4Ti4O15 (CBTi) dielectric films of Bismuth Layered Structure Dielectrics (BLSD) are examined as stacked-type dielectric capacitors for realizing excellent electric stability in capacitor device. It is revealed that the leakage current of the SBTi and CBTi is composed mainly from Schottky current for medium electric field range (about 100-350 kV/cm). The current is smaller by three order of magnitude than the BST single perovskite film, even with thinner thickness in the SBTi film. This indicates that the SBTi or CBTi film is effective for applying to high permittivity capacitor with the barium perovskite oxide family. © 2013 IEEE.

Bi-based perovskite-type oxide materials such as BiFeO3 (BFO) and Bi(Zn1/2Ti1/2)O-3 and the related compounds receive much attention and have been developed actively as important candidates for Pb-free ferroelectric materials instead of toxic Pb-based perovskite oxide materials. Recently, many researches have been reported for thin films of Bi-based materials by various film-deposition techniques for actual application of semiconductive devices, microactuators, etc. In this study, we tried preferential crystal growth of BFZT films on semiconductive silicon substrates using uniaxial-(100)-oriented LaNiO3 (LNO) buffer layer. BFO films were fabricated via chemical solution deposition (CSD) technique on platinized silicon wafer [(111)Pt/TiO2/(100)Si] and (100)LNO-coated platinized silicon [(100)LNO/(111)Pt/TiO2/(100)Si] substrates. XRD analysis indicated that the films fabricated on (111)Pt/TiO2/(100)Si substrate consisted of randomly-oriented BFZT crystal with lower crystallinity. On the other hand, the films on (100)LNO/(111)Pt/TiO2/(100)Si consisted of uniaxial-one-oriented BFZT crystal with higher crystallinity. The crystallization temperature these films were 500 degrees C, respectively. These results suggest that the BFZT crystal was grown successfully on uniaxial oriented (100)LNO plane which also had perovskite-type crystal structure. Consequently, one-oriented BFZT films were prepared on Si substrate successfully using (100)LNO buffer layer.

Thin films of (La,Sr)MnO3 (LSMO) were fabricated by industrial-versatile chemical solution deposition (CSD) technique. Well [100]-oriented LSMO films were fabricated at 650-750 degrees C by use of buffer layers of LaNiO3 buffer layer on a silicon substrate. The product of lower electrical resistivity is promising as an electrode of fatigue-free ferroelectric capacitor.

The influence of lattice distortions on TiO2 photocatalysis produced by subjecting commercially available P25 titania samples to a heat treatment in the temperature range 645-800 °C was examined it caused the initial anatase-to-rutile ratio of 81/19 to decrease to 1/99 at the highest temperature. The photoactivities of these heat-treated samples were established through the photodegradation of 4-chlorophenol (4-CP) exposed to UV irradiation alone, UV/microwave irradiation (2.45 GHz), and to UV irradiation accompanied with conventional heating at a temperature otherwise identical to that under UV/MW irradiation. Raman band intensities of pure anatase (143 cm-1), pure rutile (446 cm-1) and of the heat-treated P25 specimens were examined in situ after being exposed to microwave irradiation for about 4 min. Changes are attributed to a microwave non-thermal effect involving oxygen vacancies that affect the specimens' photoactivities as determined by subjecting samples of Evonik P25 titania (AEROXIDE® TiO2 P25) and Ishihara ST-01 TiO2 to a heat treatment in the presence of molecular hydrogen. Such treatment caused lattice distortions of both systems that affected the kinetics of degradation of the chlorophenol under various irradiation conditions. UV/visible absorption spectra of the heat/H2-treated specimens displayed a broad unresolved absorption envelope at wavelengths above 400 nm that has been attributed to oxygen vacancies and thus to F-type color centers in accord with an earlier study by Kuznetsov and Serpone. The presence of such defects, particularly in the heat/H2-treated samples, and the influence of the microwaves caused the photodegradation kinetics for the 4-CP to be enhanced significantly. © 2013 Elsevier B.V.

SrBi4Ti4O15 (SBTi) and CaBi4Ti4O15 (CBTi) dielectric films of bismuth layered-structure dielectrics (BLSD) are prepared on Pt(100) film for constructing stacked-type dielectric capacitors; it is observed that they are c-axis single-oriented crystalline films. Compared with the perovskite barium titanate family of (Ba,Sr)TiO3 (BST), it is observed that the SBTi film keeps a low leakage of 10(-7) A/cm(2) at 250 kV/cm, which is smaller by an order of magnitude than the BST film, even with thinner SBTi film. The temperature coefficient of capacitance (TCC) of the SBTi or CBTi film is about 100 to 250 ppm/K and is much smaller than that of the perovskite BST film. Because the SBTi and CBTi films have opposite polarities of TCC in this experiment, they are expected to cancel out the temperature dependence in the SBTi/CBTi composite capacitor. These results indicate that the BLSD films of SBTi and CBTi are effective for application in high-temperature and high-permittivity capacitors with the practical barium perovskite oxide family.

The solubility of a titanium (Ti) complex, titanium diisopropoxide bis(dipivaloylmethanate) [Ti(Oi-Pr)(2)(dpm)(2)], in supercritical carbon dioxide (scCO(2)) fluid was measured under various fluid temperatures and pressures to clarify its effect on supercritical fluid deposition (SCFD) for titanium dioxide (TiO2) films, by means of the extraction method with 2-propanol as the extracting solvent and UV-vis spectroscopic analysis. The solubility which is expressed by molar ratio of Ti complex to CO2, mu, decreased with the fluid temperature, T-f, from 40 to 60 degrees C, while it increased rapidly with the fluid pressure, P-f, from 6 to 10 MPa and then increased gradually with P-f from 10 to 20 MPa. The behavior was analyzed by Chrastil's equation model. The deposition rate of TiO2 films by SCFD was understood to be proportional to the difference in the mass concentration of Ti complex, S, between in the bulk transport medium and vicinity of the substrate surface. (c) 2011 Elsevier B.V. All rights reserved.

Epitaxial (1-x)BaTiO3-xBi(Mg0.5Ti0.5)O-3 films with x = 0 - 0.9 were grown on (111) cSrRuO(3)//(111)SrTiO3 substrates by pulsed laser deposition (PLD). Plotting the temperature where dielectric constant reaches a maximum {T[epsilon(r)(max.)]} versus Bi(Mg-0.5,Ti-0.5)O-3 content present minimum at x = 0.1. On the other hand, the remanent polarization (Pr) and the effective transverse piezoelectric constant [d(33)(eff.)] showed minimum at 0.1 and 0.2, respectively, but increased with the increase of x in (1-x)BaTiO3-xBi(Mg0.5Ti0.5)O-3 above these values. These results show the simultaneous increase of T[epsilon(r)(max.)] and d(33)(eff.) for the films above x = 0.2 that normally showed treads off characteristics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704384]

BiFeO₃はPb含有強誘電体を代替する有力な材料の候補として、近年その研究開発が急速に進められている。本研究では酸化物単結晶基板よりも汎用性の高いSiウェハ上での材料合成を念頭に置き、LaNiO₃層ならびにCa₂Nb₃O₁₀ナノシートなど、同じくペロブスカイト型結晶構造を有する界面層を成長核として利用したBiFeO₃薄膜材料の結晶性向上と結晶配向性の制御を試みた。BiFeO₃薄膜試料は界面層を形成した (111)Pt/TiO₂/(100)Si基板上に化学溶液法により堆積された。その結果、良好な結晶性を有する(100)BiFeO₃結晶が基板面方位に対して一軸配向成長する事が確認された。

Films of solid solution in KNbO₃--NaNbO₃(KNN) were deposited at 240 °C on (100)_\text{cSrRuO₃$\varparallel$(100)SrTiO₃substrates by the hydrothermal method. (K_xNa_1-x)NbO₃films with $x = 0{\mbox{-- } }1.0$ were synthesized by changing the fraction of KOH in a solution of KOH and NaOH. The $x$ in (K_xNa_1-x)NbO₃continuously changed with the volume fraction of KOH, while the deposition amount strongly depended on $x$. Epitaxial films with {100} orientation were obtained in the entire composition range and their out-of-plane lattice spacing changed with $x$. All the films showed ferroelectricity and their remanent polarization became larger than what above $x = 0.58$.

Thin films of SrBi(4)Ti(4)O(15), a kind of bismuth layer-structured dielectrics (BLSDs), were prepared on platinized silicon wafers buffered by perovskite-type oxide interface layers, (100)LaNiO(3)/(111)Pt/TiO(2)/(100)Si and (001)Ca(2)Nb(3)O(10)-nanosheets/(111)Pt/TiO(2)/(100)Si, by chemical solution deposition (CSD). The Ca(2)Nb(3)O(10) nanosheets were supported on a (111)Pt/TiO(2)/(100)Si substrate by dip coating using an aqueous dispersion, while (100)LaNiO(3) was prepared by CSD. The (00/) planes of BLSD crystal were preferentially oriented on the surface of both substrates, which is caused by suitable lattice matching between the a-(b-)axis of BLSD and perovskite-type oxide layers. The film deposition on (001)Ca(2)Nb(3)O(10) nanosheets yielded (001)-oriented BLSD films with higher crystallinity and smaller fluctuation in the tilting angle of the (001)BLSD plane than those on the (100)LaNiO(3) interface layer. The dielectric constant (epsilon(r)) of (001)-oriented SrBi(4)Ti(4)O(15) film on (001)Ca(2)Nb(3)O(10)-nanosheets/(111)Pt/TiO(2)/(100)Si substrate was approximately 190, which was significantly stable against the change of frequency and bias voltage compared with that of the randomly-oriented SrBi(4)Ti(4)O(15) film. (C) 2011 The Japan Society of Applied Physics