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A phenomenological Landau-Devonshire theory is applied to construct the thermodynamic potential of (110) oriented Ba(Zr0.08Ti0.92)O3 thin film and investigate the phase transition, ferroelectric, dielectric and piezoelectric properties. Three ferroelectric phases, such as tetragonal a1 phase, orthorhombic a2c and triclinic γ phase are stable in “misfit strain-temperature” phase diagram. Two triple points are found in the phase diagram and 90° polarization switching can occur directly between tetragonal a1 phase and orthorhombic a2c phase. Complicated phase transitions are induced by the electric field in triclinic γ phase due to the nonlinear coupling terms appeared in the thermodynamic potential. The longitudinal piezoelectric coefficient of (110) oriented Ba(Zr0.08Ti0.92)O3 thin film is smaller than that of (001) oriented film. Moreover, negative longitudinal piezoelectric coefficient can be obtained in triclinic γ phase.

The phenomenological Landau-Devonshire theory is applied to investigate the electrocaloric effects of bulk and thin film Ba(Zr0.08Ti0.92)O3 single crystals. The electrocaloric coefficient of 1.36 × 10−3 C/m2K and adiabatic temperature change of 1.0 °C are obtained in tetragonal T phase for bulk Ba(Zr0.08Ti0.92)O3 single crystal with the electric field of 50 kV/cm and field change of 200 kV/cm, respectively. Ba(Zr0.08Ti0.92)O3 thin film with tensile misfit strain has the larger electrocaloric effect in monoclinic M2 phase than that of tetragonal T phase which exists in compressive misfit strain. The compressive misfit strain does not change the maximum of electrocaloric coefficient, but enlarges the maximum of adiabatic temperature change. However, the tensile misfit strain improves the maxima of electrocaloric coefficient and adiabatic temperature change. In addition, the effects of electric field and temperature on electrocaloric effect are studied in tetragonal T phase and monoclinic M2 phase with different compressive and tensile misfit strains respectively. The large electrocaloric coefficient and adiabatic temperature change at the misfit strain of 0.4% are 7.4 × 10−3 C/m2K and 20 °C for Ba(Zr0.08Ti0.92)O3 thin film with the electric field of 50 kV/cm and the field change of 200 kV/cm, respectively. The giant electrocaloric effect in Ba(Zr0.08Ti0.92)O3 thin film may provide the potential for practical cooling device applications.

A phenomenological Landau-Devonshire theory is used to investigate the “misfit strain-temperature” phase diagram and physical properties of (001) oriented KNbO3 film. Three ferroelectric phases, such as c phase, aa phase, and γ phase, occur in the phase diagram. In-plane compressive misfit strain is beneficial to form c phase and tensile strain makes aa phase stable. Physical properties of KNbO3 film largely depend on misfit strain and electric field. At room temperature, γ phase of KNbO3 film with the tensile misfit strain has larger piezoelectric and pyroelectric coefficients than that of c phase with the compressive strain. Large piezoelectric and pyroelectric coefficients are 180 pm/V and 8.5 × 10−4 C/m2K respectively at the electric field of 100 KV/cm and misfit strain of 6.7 × 10−3, which are comparable with the experimental results of Pb(ZrxTi1−x)O3 film. Therefore, choosing the appropriate substrates can be used to improve the physical properties of KNbO3 film. In addition, the applied electric field decreases the dielectric, piezoelectric and pyroelectric properties of (001) oriented KNbO3 film.

Based on the phenomenological Landau-Devonshire theory, the phase diagram and physical properties of (110) oriented KNbO3 film are investigated. The “misfit strain-misfit strain” phase diagram at room temperature is constructed in the frame of eighth-order thermodynamic potential. Three tetragonal phases and two orthorhombic phases are stable in phase diagram due to the strain anisotropy. The large in-plane compressive or tensile misfit strains favor the tetragonal phases. Moreover, both the tensile misfit strain u1 (or u2) and compressive strain u2 (or u1) induce the orthorhombic phases. Large piezoelectric coefficient is obtained in orthorhombic phases which have the small in-plane tensile misfit strains. It makes (110) oriented KNbO3 film suitable for applications in electromechanical devices.

Orientation dependence of phase diagrams and physical properties of Ba0.6Sr0.4TiO3 films are investigated by using a phenomenological Landau-Devonshire theory. New ferroelectric phases, such as the tetragonal a 1 phase and the orthorhombic a 2 c phase in (110) oriented film and the monoclinic M A phase in (111) oriented film, appear in the “misfit strain-temperature” phase diagrams as compared with (001) oriented film. Moreover, the phase diagrams of (110) and (111) oriented films are more complex than that of (001) oriented film due to the nonlinear coupling terms appeared in the thermodynamic potential. The dielectric and piezoelectric properties largely depend on the misfit strain and orientation. (111) oriented film has the better piezoelectric property than (110) oriented film. Furthermore, the compressive misfit strain is prone to induce the larger piezoelectric property than tensile misfit strain.

In this work, IGZO ink was prepared by dissolving gallium chloride, indium chloride, zinc acetate dihydrate and monoethanolamine (MEA) in 2-methoxyethanol. Five types of IGZO ink were prepared with different molar ratios of In:Ga:Zn: A(10:1:10), B(10:3:10), C(10:5:10), D(10:7:10), E(10:9:10). Based on the above-prepared ink, IGZO films were printed by a FujiFilm Dimatix printer (DMP-2831) on the glass, and then annealed with differenYut temperatures. The film samples with different Ga concentrations and annealing temperatures were investigated to study the uniformity, optical transmittance and electron mobility.

A phenomenological Landau-Devonshire theory is applied to investigate the phase diagrams and physical properties of (110) oriented Ba x Sr 1 − x TiO 3 films. New ferroelectric phases, such as the tetragonal a 1 phase and the orthorhombic a 2 c phase, appear in the “misfit strain-temperature” phase diagrams for (110) oriented films compared with that of (001) oriented films. Moreover, the orthorhombic a 2 c phase, and the tetragonal c phase and the triclinic γ phase are stable at low temperature for x = 0.5 and x = 0.7 , respectively. The ferroelectric, dielectric, and piezoelectric properties strongly depend on the misfit strain and electric field. (110) oriented Ba 0.7 Sr 0.3 TiO 3 film has the larger ferroelectric polarization and piezoelectric coefficient than that of Ba 0.5 Sr 0.5 TiO 3 film. The giant piezoelectric coefficient of 340 pm / V is obtained at the electric field of 50 KV / cm in (110) oriented Ba 0.7 Sr 0.3 TiO 3 film, which is comparable with the values of Pb ( Zr 1 − x Ti x ) O 3 and ( 1 − x ) Pb ( Mg 1 / 3 Nb 2 / 3 ) O 3 − xPbTiO 3 films. It makes (110) oriented Ba x Sr 1 − x TiO 3 films suitable for applications in electromechanical devices.

The phase diagram and pyroelectric effect of (110) oriented Pb ( Zr 1 − x Ti x ) O 3 thin films with different Ti composition are investigated by a phenomenological Landau–Dovenshire theory. The tetragonal ( a 1 ) phase, the orthorhombic ( a 2 c ) phase, and the triclinic (γ) phase are stable. The compressive misfit strain favors the orthorhombic ( a 2 c ) phase, whereas the tensile misfit strain makes the triclinic (γ) phase and the tetragonal ( a 1 ) phase stable. At room temperature, the misfit strain induces the first order phase transition from the orthorhombic a 2 c phase to the triclinic γ phase in the Pb ( Zr 1 − x Ti x ) O 3 (x=0.4, 0.5, 0.6) thin films. Moreover, even in the γ phase of Pb ( Zr 1 − x Ti x ) O 3 (x=0.4, 0.5) thin films, the first order γ1–γ2 phase transition may happen with increasing the tensile misfit strain. The Pb ( Zr 0.5 Ti 0.5 ) O 3 thin film with the Ti composition around the morphotropic phase boundary has the largest dielectric and pyroelectric properties, which is in agreement with the experimental result. A critical electric field exists and results in the non-monotonic variation of dielectric and pyroelectric properties with the misfit strain in Pb ( Zr 0.5 Ti 0.5 ) O 3 thin film. The positive pyroelectric coefficient is obtained in the γ2 phase of Pb ( Zr 1 − x Ti x ) O 3 (x=0.4, 0.5, 0.6) thin films.

Aluminum doped zinc oxide (AZO) transparent conducting films were dynamically deposited on corning glass substrates in an in-line sputtering system operated at mid-frequency sputtering mode with excitation frequency of 40 kHz. This study addressed the surface structure as well as the electrical and optical properties after wet-chemical etching. With the increase of substrate temperature, the dominant orientation of the as-deposited films changes from (0 0 2) to (1 0 3). After wet-chemical etching, due to the quick etching rate of the (0 0 2) plane relative to the (1 0 3) plane, the surface morphology of the films deposited at different temperatures show a transition from craterlike to granular surface morphology. The experimental results demonstrate that the crystal orientation of the as-deposited films plays an important role for the etching behavior of the films.

The texture and grain size of a Mg–3Al–1Zn alloy sheet were controlled by applying equal-channel angular rolling and high-speed-ratio differential speed rolling in sequence. A texture that has rarely been reported in any other sheet fabrication processes was developed in which some fiber axes of the largely weakened basal fiber texture tilted with spreading in the rolling direction. The microstructure and texture correlated well with the mechanical responses.

TiO 2 nanoarrays were successfully synthesized by an ultrasonic method in TiCl 4 /HCl solution. The products were investigated by XRD, SEM, TEM and SAED techniques. The results indicated that the products were pure single crystal rutile TiO 2 nanoarrays. The size of the arrays ranged from 20 to 300 nm with each of them consisting of small nanorods of about 8 nm in diameter and 200 nm in length. The growth mechanism of the TiO 2 nanostructure was also discussed. The photocatalytic activity of the products was investigated by photodegradation of aqueous brilliant red X-3B solution. It was found that the arrays exhibited better photocatalytic activity both than TiO 2 nanorods and Degussa P25.

Ba0.6Sr0.4TiO3 (BST) films with different thickness were grown on (0 0 1) MgO substrates by pulsed laser deposition. Effects of thickness and post-deposition annealing on the crystal structure and dielectric properties of BST films are investigated. Enhancement of the crystal structure through post-deposition annealing is analyzed from the viewpoint of energy minimization principle of stable state. The best dielectric properties are obtained for the 500-nm-thick BST film with post-deposition annealing at 1000 degrees C in flowing O-2 atmosphere. Based on the high-quality BST film, a distributed microwave phase shifter was fabricated, and promising high-frequency device performance is achieved. (c) 2007 Elsevier B.V. All rights reserved.

A single buffer layer of LaMnO3 for YBa2Cu3O7−x (YBCO) coated conductors has been grown on textured Ni substrate using pulsed laser deposition (PLD). Detailed X-ray diffraction (XRD) studies showed that the LaMnO3 single buffer layer had a good out-of-plane and in-plane texture with a full width at half maximum of 5.2° and 9.9°, respectively. The scanning electron microscopy image revealed a dense, smooth, and uniform surface. The single LaMnO3 buffer layer has been proved to be a very effective diffusion barrier layer against Ni and oxygen diffusion and a good template for subsequent growing high critical current density YBa2Cu3O7−x films.

Nanocrystalline anatase TiO2 films were prepared from colloidal suspensions using particles with a size of 12 nm. Their structure was examined by Raman spectroscopy and X-ray diffraction (XRD). The as-prepared specimens exhibit exclusively features due to the anatase phase of TiO2 (e.g., the Eg, B1g and A1g vibration modes in Raman spectroscopy and the characteristic diffraction peaks in XRD). Isochronal annealing of the films in air at temperatures of up to 1320 K effected clear structural changes, observed both in Raman and XRD: the crystallite size increases from ∼13 nm to ∼90 nm between 720 K and 1170 K, with the crystallites remaining in the anatase phase. A phase transition to the rutile phase of TiO2 occurs in the temperature range 1170–1320 K and the average crystallite size increases to ∼160 nm.

Magnetic and dielectric properties of a polycrystalline GaFeO3 sample prepared by a solid-state reaction have been investigated. A ferrimagnetic phase transition TN of the material was identified at a temperature of 225 K. An anomaly on the permittivity as a function of temperature has been observed near its magnetic transition point TN, which could be induced by the magnetoelectric coupling between its electric and magnetic orders. At low temperature, T< T N, the permittivity variation �e depends on magnetization M and shows clearly a linear relationship between �e and M 2 , which indicates that a dielectric and magnetic correlation exists in the compound. Furthermore, its dielectric relaxation process is discussed in the temperature interval of 77–300 K. (Some figures in this article are in colour only in the electronic version)

In order to clarify the basic reason why Ce doping can dramatically decrease the leakage current in Ba0.5Sr0.5TiO3 (BST) as reported in our previous work (Wang et al 2005 J. Phys. D: Appl. Phys. 38 2253), we have employed x-ray photoelectron spectroscopy (XPS) and the optical transmittance technique to study the electronic structure of undoped and 1.0 at% Ce-doped BST (CeBST) films fabricated by pulsed laser deposition. XPS results show that Ce doping has a strong influence on the valence band and core levels of BST films, and that the Fermi level is lowered by about 0.35 eV by Ce doping. Optical transmittance measurements demonstrate that the energy gap is expanded with Ce doping. These Ce-doping effects can induce an increase in the barrier height for the thermionic emission and eventually reduce leakage current in CeBST thin films.

Chemical solution deposition is a promising technique for fabrication of high-temperature superconducting films and oxide buffer layers due to its reproducibility and low cost. In this work, Y2O3 buffer layers were prepared on (100) LaAlO3 substrates by mental organic deposition method using trifluoroacetate. The resulting Y2O3 films crystallized as a single phase at 900°C and showed a low degree of c-axis orientation. The scanning electron micrography showed that the surface of the films was smooth with a uniform grain size of approximately 10 nm.

Perovskite-based SrNb0.2Ti0.8O3/La0.7Sr0.3MnO3 bilayer films were grown on (001) SrTiO3 substrate. By means of in situ transmission electron microscopy, lattice expansion and double periodicity were identified in both plan-view and cross-section La0.7Sr0.3MnO3 films under electron irradiation for 25 s. After the electron beam was removed from specimens, the original perovskite structure recovered within 10 min. However, when irradiation time was more than 1 min, the original perovskite structure could not recover and became an amorphous phase or a cavity created by irradiation. According to first-principle calculation and electron diffraction pattern simulation, formation mechanism of the lattice expansion and double periodicity is proposed based on oxygen deficiency during electron irradiation.

The deformation and fracture behaviour of a porous FVS0812 aluminium alloy prepared by spray deposition was investigated using compression testing. Rapid densification of the porous alloy was observed before a height reduction of ~50%. The optimum strain rate and deformation temperature to achieve maximum density were determined. Microstructural evolution involved the following stages: breakup of boundaries between adjacent particles; plastic deformation of particles; and collapse of large pores into various smaller pores and their disappearance. A strain hardening phenomenon occurred at all strains when compression was carried out at at 573 and 673 K, while a recovery mechanism came into operation at 773 K and a true strain of 0.2. The critical strain for the occurrence of strain softening in the porous alloy was much higher than that for the fully dense alloy. The fracture criteria curve of the porous alloy was a straight line, with a slope of ~0.45268 at high temperature and ~0.47636 at room te...

The efficient growth of ordered thin oxide films on Ni (1 1 1) using low NO2 gas exposures under ultrahigh vacuum conditions has been achieved. The reaction mechanism of NO2 on Ni (1 1 1) at 500–600 K changes from total decomposition to partial dissociation into NO and O after a critical surface adatom coverage has been attained. Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) reveal the creation of an intermediate NiO (1 0 0) phase, followed by the eventual formation of clean NiO (1 1 1) overlayers. Reflection absorption infrared spectroscopy (RAIRS) using CO molecules as probes of the surface adsorption sites present confirms the conversion of Ni0 to Ni2+ during the oxidation process.

Undoped and Co-doped Ba0.5Sr0.5TiO3 thin films have been fabricated by pulsed laser deposition to explore low dielectric loss and high tunability materials for tunable microwave devices. The crystal structure and surface morphology have been characterized by X-ray diffraction and atomic force microscopy. The influence of Co-doping on lattice parameter of Ba0.5Sr0.5TiO3 materials has been investigated, and the results show that the variation of lattice parameters with Co concentration is different between targets and thin films. The dielectric loss in the Ba0.5Sr0.5TiO3 thin films with 0.2 and 1 at% Co are 0.064 and 0.039 at frequency of 100 kHz, respectively, which are lower than that of undoped Ba0.5Sr0.5TiO3 thin films. The tunability of permittivity of the Ba0.5Sr0.5TiO3 thin films are 34.6% and 18.7% with 0.2 and 1.0 at% Co-doping at applied electric field 200 kV/cm. (C) 2003 Elsevier B.V. All rights reserved.

Highly c-axis oriented MgB2 thin films with T-c(onset) of 39.6 K were fabricated by magnesium diffusing into pulsed laser deposited boron precursors. Estimation of critical current density J(c), using hysteresis loops and the Bean model, gave the value of 10(7) A/cm(2) (15 K, 0 T), which is one of the highest values ever reported. The X-ray photoemission spectra of the MgB2 thin film revealed the binding energy of Mg 2p and B 1s are at 49.4 and 186.9 eV, respectively. The Raman spectra showed a typical broad band centered at 620 cm(-1) with shoulders at 294, 410 and 730 cm(-1) respectively. The dominant band at 620 cm(-1) is interpreted as the first-order Raman response from the E-2g phonon of MgB2 and the other three bands are properly originated from the phone density of states in MgB2. (C) 2003 Elsevier Science B.V. All rights reserved.

The paper reports a remarkably simple method for fast fabrication of double-sided MgB 2 thick films by electrophoresing precursor boron powders on various metallic substrates followed by an ex situ annealing in magnesium vapor. Both sides of the films are homogeneous in thickness and composition, and no significant difference in T c and J c is found between the MgB 2 thick films on both sides of metals. Scanning electron microscopy on both sides of the double-sided films show dense and homogeneous structure consisting of MgB 2 grains below 1 μm. The X-ray diffraction and resistance measurement of the MgB 2 thick films on different metals show that the films are random oriented and have the onset superconducting temperature T c in the range of about 32–38 K. Estimates using hysteresis loops and Bean model give the critical current densities of the thick films are above 10 5 A/cm 2 in zero field and 5 K. The irreversibility fields of the thick films are comparable to those obtained from the dense wire.

The crystal structure and superconductivity of MgB2 thin films grown on various oxide substrates were investigated by X-ray diffraction and resistance measurement. The films were prepared by a two-step method, in which precursors B films were annealed in Mg vapor at 900○C. The X-ray diffraction shows that the MgB2 films grown on C–AL2O3, R–AL2O3, and MgO (001) are c-axis oriented while the films grown on SrTiO3 (001), LaAlO3 (001), and ZrO2 (001) are aligned with the (101) direction normal to the substrate planes. All the grown films show superconductivity and their transition temperature varies with the substrates in the range of 34–39 K. We think that the transition temperature variation is probably due to the lattice matching between the film and the substrate, as well as the interdiffusion at the film/substrate interface. The experimental results suggest that if there is no severe interdiffusion at the film/substrate interface in the high temperature annealing process, more substrates could be used for the growth of MgB2 films using the two-step method.

The effect of 4, 6 and 8 (mass%) Ce additions on the microstructure and creep resistance of the Mg-2.5Zn alloy was investigated by tensile creep test in the temperature of 200 °C, 225°C with the tensile stress of 60 MPa and tensile test in room temperature. The microstructure and phase composition of these alloys were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). The results showed that the grain sizes of Mg-2.5Zn

Multilayer oxides of SrNb0.1Ti0.9O3/La0.8Sr0.2MnO3/SrTiO3 have been grown by computer-controlled laser molecular beam epitaxy and characterized by transmission electron microscopy. Electron microdiffractions and high-resolution imaging reveal that the as-prepared thin film of La0.8Sr0.2MnO3 with thickness of 200 nm is epitaxially grown on the SrTiO3(001) substrate and the SrNb0.1Ti0.9O3 with thickness of 250 nm epitaxially on the as-received La0.8Sr0.2MnO3 film. The microstructures in the La0.8Sr0.2MnO3 film are clarified in terms of the oriented microdomains. In contrast, microstructures in SNTO are featured by the formation of superstructures due to charge ordering. Crystallographic relationships of these domains are discussed on the basis of an orthorhombic cell and rationalized by theoretical calculations based on a geometrical model.

More than 10 kinds of perovskite oxide thin films and their heterostructures have been successfully fabricated on SrTiO3(STO) (0 0 1) substrates by laser molecular beam epitaxy (laser MBE). Measurements of atomic force microscopy (AFM) and high-rt solution transmission electron microscopy (HRTEM) reveal that the surfaces and interfaces are Atom level smooth. The unit cell layers and the lattice structure are perfect. The enhancement of secund-harmonic generation (SHG) in BaTiO3/SrTiO3 9BTO/STO) superlattices and the thickness dependent structural characteristics of BaTiO3 (BTO) thin fillns were observed. The all-prrovskite oxide P-N junctions have been successfully fabricated and better I-V curves were observed. (C) 2001 Elsevier Science B.V. All rights reserved.

In an earlier work, 11B NMR spectra obtained from a series of as-quenched Fe-B-C amorphous alloys revealed two distinct peaks centered at 34.7 and 36.3 MHz, which were attributed to regions with short-range order (SRO) characteristic of body-centered tetragonal Fe3B (bct-Fe3B) and orthorhombic Fe3B (o-Fe3B), respectively. It was determined that the addition of C favors the formation of o-Fe3B-like SRO and this was correlated with the enhancement of the soft magnetic properties. In this report, 11B NMR is utilized to study the evolution of the above phases, along with bcc α-Fe, in the Fe80B20-xCx alloys (x = 0, 2, 4, 7 and 9) for various thermal treatments. Consistent with the earlier work, it is found that the addition of C is necessary for o-Fe3B-like SRO formation upon thermal treatment. In particular, annealing the x = 0 alloy at both 460°C and 840°C results in bct-Fe3B precipitates plus bcc α-Fe. However, for the alloys with x > 0, the annealing treatment at 460°C results in some o-Fe3B precipitates along with bct-Fe3B and bcc α-Fe; the amount of o-Fe3B increases with the C content. The same situation occurs for the 840°C heat treatment with the o-Fe3B precipitates occurring to a greater degree and the bct-Fe3B SRO being completely suppressed for x ≥ 4. These results show that the C atoms play a crucial role in the formation and stability of the o-Fe3B SRO which is developed during the thermal treatments.

The structure and quality of AlxGa1-xAs/AlyGa1-yAs/GaAs step multi-quantum wells grown by molecular beam epitaxy on (001) GaAs substrates have been studied by means of X-ray double crystal diffraction. We demonstrate that for such a complicated structure it is necessary to consider the influence of beam flux variations on layer thickness and composition in order to obtain good agreement between theoretical calculated rocking curves and their experimental counterparts. As a result, the structural parameters were simply determined, and the information about the beam flux variation was obtained. Such results may explain the difference between the design structure and that obtained.

New surface acoustic wave interdigital transducer (IDT) and unidirectional transducer (UDT) are described. Using lift off-etching method or lift off-anodic oxidation method, we can get narrow gaps, with good insulation, between electrodes. Experimental results show directivities of 6 dB/transducer at 438 MHz and 17 dB/transducer for its second harmonic at 868.5 MHz. Also, minimum insertion loss of 3.6dB for a low loss filter at 440MHz is obtained.

We report here the preparation of the superconducting Bi-Sr-Ca-Cu-O thin films on SrTiO 3(100) substrates by a Nd:YAG laser, which provides laser pulses with wavelength of 1.06µm and pulse width of 200ns. After the heat treatment at 850°C for half an hour in oxygen flow, the samples exhibit superconductivity with the zero resistance at 66.8K and the onset temperature around 84K. X-ray diffraction analyses show that the samples have the preferred orientation with the c-axis perpendicular to the substrate.

The calculation of local resistance of gas-liquid two-phase flow through an orifice is a problem yet to be solved in engineering design. A new model allowing the calculation was developed. The calculation on which the model is based was verified by tests carried out on an air-water two-phase flow test bed and proved to be in good agreement with the experimental results. By comparing the results of the calculation with data from experiments on steam-water systems, the authors also found that, on the whole, this model fits the system of steam-water mixture, thus giving it a wide range of application. Morevoer, the accuracy of the calculation can also meet the general requirements of engineering design.