Lead titanate (PbTiO3) is a ferroelectric/piezoelectric material widely used in medical ultrasound transducers and infrared detectors. It is also important as an end member of morphotropic solid-solution systems such as Pb(Zn1/3Nb2/3)–PbTiO3 (PZN–PT) and Pb(Mg1/3Nb2/3)–PT (PMN–PT) that exhibit exceptional electromechanical properties as oriented single crystals. The float-zone technique has been used to grow pure crystals of lead titanate. To the best of the authors’ knowledge, this is the first time that the growth of this compound by the float-zone technique has been reported. The principal advantage of the float-zone technique is that no container is required so that a uniform distribution of chemical constituents can be obtained while eliminating problems of heterogeneous nucleation and metal contamination at the container wall. Although large single crystals were not obtained in the current study primarily due to instabilities of the molten liquid zone, the combined results of characterization by electron probe microanalysis, x-ray diffraction, specific heat, and dielectric permittivity measurements show that the float-zone crystal growth technique can produce lead titanate crystals of high chemical and phase purity. However, the results show that to obtain large single crystals, the stability of the molten zone at low cooling rates must be improved.

The influence of uniaxial prestress on dielectric and piezoelectric performance was studied for soft lead zirconate titanate piezoceramics. High electric field induced polarization and longitudinal/transverse strain were measured at different compression preload levels of up to −400 MPa. The parameters evaluated included polarization/strain outputs, dielectric permittivity, piezoelectric constants, and dissipation energy as a function of the mechanical preload and electric-field strength. The results indicate a significant enhancement of the dielectric and piezoelectric performance within a certain prestress loading range. At much higher stress levels, the predominant mechanical depolarization effect makes the material exhibit hardly any piezoeffect. However, the enhanced performance achieved by a small stress preload is accompanied by an unfavorable increased hysteresis, and consequently, increased energy loss, which is attributed to a larger extrinsic contribution due to more non-180° domain switching induced by the combined electromechanical load.

The superconducting properties of air-processed melt-textured growth Sm–Ba–Cu–O samples with addition of small amounts (0.004 wt%, 0.4 wt%, 4 wt%) of nano-sized Sm2BaCuO5 particles (nm211) were studied. The microstructure observations show that the size distribution and morphology of the 211-particles of the nm211-doped samples are similar to that of the control (undoped) samples. However, except for the 4 wt% nm211-doped sample, both Tc (critical temperature) and Jc (H, T) (critical current density) are enhanced in nm211-doped samples, and the Jc–H curves are different from those of control samples. The effect of nm211 particles on Jc enhancement is larger at high magnetic fields (>1 T at 77 K) than at low magnetic fields (0∼1 T). The dominant pinning mechanism by analyzing the Jc (H, T) data using the scaling theory indicate that the nm211-doped samples are originated from Δκ pinning (i.e., Tc variation); on the other hand, the control samples are originated from normal pinning (i.e., nonsuperconducting crystalline defects). It is proposed that nano-sized compositional fluctuations in the RE1+x Ba2−x Cu3O y matrix, which are products of nm211 particles and liquid peritectic reaction, act as the source of Δκ pinning centers.

Using molecular dynamics to simulate behavior of polymer surfaces during scratch testing, we report the first results of computer simulations of scratch behavior of noncrystals. A previously described procedure for creating realistic polymeric materials on the computer [W. Brostow, A.M. Cunha, and R. Simoes, Mater. Res. Innovat. 7, 19 (2003)] and used until now to simulate mechanical behavior of metals [S. Blonski, W. Brostow, and J. Kubat, Phys. Rev. B 49, 6494 (1994)] and one- and two-phase polymers [W. Brostow, A.M. Cunha, J. Quintanilla, and R. Simoes, Macromol. Theory Simul. 11, 308 (2002); W. Brostow, A.M. Cunha, and R. Simoes, Proc. Ann. Tech. Conf. Soc. Plastics Engrs. 60, 3105 (2002)] was applied. While experiments provide only the macroscopic penetration depth and the recovery (healing) depth, the simulations give the behavior of each macromolecular chain segment at each moment in time. We report results for one-phase polymers and also for systems with varying concentrations of a liquid crystalline (LC) second-phase that acts as a reinforcement. We relate the local structure to scratch resistance and recovery. The orientation of the chemical bonds is a major factor. The presence of a LC phase improves the tribological properties; however, the effect is not as significant as might have been expected.

The electrical breakdown strength of TiO2 nanoparticle-filled low-density polyethylene (LDPE) nanocomposites was investigated. It was found that the surface water on the nanoparticles played a very important role in determining the breakdown strength. The breakdown strength at 63.2% cumulative failure probability (E0) for the composites filled with dried nanoscale TiO2 was similar to that of neat LDPE and 50% higher than that for the samples filled with as-received nanoscale TiO2. This increase was due to a better dispersion, a better interface, and a morphology change of the matrix. It was also found that surface modification of nanoscale TiO2 had a significant influence on the breakdown strength. N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS)-coated TiO2-filled samples showed about 40% higher E0 than that of uncoated, as-received TiO2-filled samples. This was mainly due to enhanced electron scattering because of the presence of polar groups in AEAPS.

Microcontact impedance spectroscopy in conjunction with conventional impedance techniques has been performed to elucidate microstructural and compositional inhomogeneities in polycrystalline Mn–Zn ferrites. Microcontact studies reveal the occurrence of oxygen stoichiometry gradients in these typically prepared ferrite ceramics together with a strong spatial resistance variation from boundary to boundary. This leads to a reinterpretation of the conventional impedance spectra of ferrites.

The kinetics of borosilicate glass film deposition on silicon using boron nitride as a solid source was investigated. Experimental data on the thickness of deposited films as a function of temperature and process times under controlled atmospheric conditions was obtained. A 33-kW rapid thermal processing infrared furnace was used to minimize temperature and gas phase transients experienced on the commercial scale. The thickness and composition of the borosilicate glass films were measured using scanning Auger spectroscopy, and the thickness of the films as a function of time for various temperatures are presented. The results suggest a rapid transition to diffusion-controlled deposition with an activation energy of 2.77 ± 0.5 eV. The partial pressure of water vapor was found to have a potentially significant effect on the rate of film growth.

With the help of instrumented indentation, the mechanical behavior of a variety of biological systems was studied: the waxy zone of the pitcher plant (Nephenthes alata) adapted for attachment prevention, the head-to-thorax articulation system of a beetle (Pachnoda marginata) as an example of friction minimization, and the wing arresting system of the dung beetle (Geotrupes stercorarius) adapted for mechanical interlocking. We demonstrate that nanoindentation can successfully be applied to compliant and highly structured biological composite materials. Measuring the mechanical performance of these surfaces can provide important information for understanding the overall functioning of these systems. Tests on fresh and dried samples show the influence of desiccation on the results and point out the importance of native conditions during the measurements. However, these preliminary results also point to current limits of the test method and the need for adapting it and current theories to meet the specific requirements of biological materials.

The fabrication and applications of porous anodic alumina (PAA) have been studied for decades. Recently, preparation of PAA template directly formed on Si has been developed to enhance the performance of the fabricated nanostructures. However, less attention is paid to the anodization mechanism of the Al film on the Si substrate. In the current study, the PAA template was fabricated on Si of which an interlayer was sandwiched between the Al film and the Si substrate. The anodization behavior of the Al film, especially at the alumina–substrate interface, was investigated through the observation of the variation of oxidation current and the structural change of alumina. Different degree of dissolution at the pore base of alumina was revealed when a different interlayer was introduced, leading to the formation of the arched pore bottom. At the same time, difference in the variation of current was also observed as the pore base reached the alumina–Si interface. These features were different from those observed in conventional anodization of Al foils. The findings in this study are of scientific and technological importance for the template-mediated growth of nanostructures, especially for those to be integrated into Si devices.

The effect of ZrO2–3 mol/ Y2O3 sol-gel thin coatings on the fracture of soda-lime glass is investigated. For this purpose, a recently developed strength measurement procedure—based on making a brittle material flex on top of a soft substrate by applying a load with a spherical indenter to the top surface of the system—is used. Results suggest significant variation of both the average fracture strength and the Weibull modulus on coated glass slides. It is suggested that the origin of such variations can be attributed to a certain chemical degradation of the glass during the coating process. This chemical attack produces a highly homogeneous flaw population on the glass surface which governs its fracture behavior. Implications of this work for the practical use of coated glass layers are discussed.

Undoped and manganese-doped zinc gallate powders and thin films have been synthesized via the hydrothermal route from aqueous solutions at a pH between 9.5 and 12.5. The chemical composition and the crystal size of the synthesized powder have been studied as a function of pH, temperature, and the composition of the precursor solution, such as the type of hydroxide used and the zinc, gallium, and lithium content. Specimens have been analyzed by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersive x-ray spectroscopy, thermogravimetry, and inductively coupled plasma atomic emission spectroscopy. It is shown that crystallite size and chemical composition strongly depend on the solubility of the gallium species within the solution, which appears to determine the number of ZnGa2O4 nuclei per unit volume. Crystals of a few micrometers in size can be synthesized from solutions where Ga is very soluble (e.g., pH ≥ 11), whereas when Ga is not very soluble, the synthesis product is nanocrystalline. Thermogravimetric studies indicate that a considerable amount of OH− is incorporated at the oxygen sites (every 5th to 10th site). Hydrothermal growth of heteroepitaxial zinc gallate thin films has been carried out on (111) MgAl2O4 and (00.1) LiNbO3 substrates. Heteroepitaxy is based on a coincident pattern of oxygen sites in the two structures; that is, (111)ZGO ∥ (111)MAO and (111)ZGO ∥ (00.6)LNO for the out-of plane orientation and (1¯10)ZGO ∥ (1¯10)MAO and (1¯10)ZGO ∥ (1¯10)LNO for the in-plane orientation, respectively. The thin films cover the substrate completely and consist of oriented grains of up to several hundred nanometers in size. In general, the films are twinned with two variants (in separate grains) that are related by a 60° rotation around [111]. This twinning can only be suppressed at high pH and high temperature and only on the MgAl2O4 substrates.

Li-doped NiO epitaxial films with high electrical conductivity and atomically flat stepped surfaces were fabricated by a combined technique of pulsed laser deposition and subsequent annealing. It was determined that subsequently annealing at temperatures as low as 600 °C significantly decreased electrical conductivity due to Li evaporation when the film surface was not protected from Li evaporation. To suppress Li evaporation, a yttria-stabilized-zironia plate was used to cover the film surface, which raised the annealing temperature up to 1300 °C while maintaining a high Li concentration and electrical conductivity. Thermally annealing at this temperature also improved crystal quality and formed epitaxial films with atomically flat stepped surfaces. The films were single crystalline at least in observation areas, 10 μm × 10 μm. A reasonably large Hall mobility approximately 0.05 cm2/Vs similar to that reported for bulk single-crystal NiO and a visible-light transmission in excess of 75% were obtained on 120-nm-thick films. Although annealing at higher temperatures such as 1400 °C can further improve the structural and optical properties, the Li concentration in the films was decreased to <3% of the as-deposited film.

Several new bulk metallic glasses based on Fe–Y–Zr–(Co, Cr, Al)–Mo–B, which have a glass-forming ability superior to the best composition Fe61Zr10Co7Mo5W2B15 reported recently, have been successfully developed. The as-cast bulk amorphous alloys showed a distinctly high thermal stability with glass-transition temperatures above 900 K, supercooled liquid regions above 60 K, and high strength with Vickers hardness values larger than HV 1200. The suppression of the growth of primary phases in the molten liquids and the resultant low liquidus temperatures were found to be responsible for the superior glass-forming ability in these new alloys. It was found that the addition of 2% Y not only facilitated bulk glass formation, but the neutralizing effect of Y with oxygen in the molten liquids also improved the manufacturability of these amorphous alloys.

Formation of iron oxide nanoparticles within the internal cages of Na–Y zeolites was investigated. Sodium ions within the zeolites were replaced with iron(II) ions. Elemental composition studies showed a significant amount of iron in the exchanged sample. NaOH and dropwise additions of H2O2 at 60 °C triggered formation of zeolite–iron oxide systems. X-ray diffraction (XRD) patterns showed diminishing zeolite peaks along with evolution of peaks corresponding to γ-Fe2O3 and α-Fe2O3 with increasing NaOH concentration. Morphological changes from hexagonal-shaped zeolite to clusters of fine particles were observed under scanning electron microscope. Particles with about 15-nm diameter were detected by transmission electron microscopy. γ-Fe2O3 crystallites of 13.4 nm were determined from the broadening of XRD peaks. The magnetization curves of samples (precipitated using NaOH with concentrations of 2.0 M and above) showed absence of hysteresis and passed through the origin, indicating the particles are superparamagnetic. Gas adsorption–desorption measurement of the system precipitated with 2.0 M NaOH revealed a 26% increase in its specific surface area, indicating the presence of nanometer-sized particles within the zeolites.

The deformation behavior of Ti-based bulk metallic glass (BMG) and metallic glass matrix composite (MGMC), both having a multistep crystallization behavior upon heating, has been investigated in the supercooled liquid region. The BMG deforms homogeneously and exhibits moderate elongation to failure due to its multistep crystallization behavior, but shows a significant variation of the flow stress during deformation. For the MGMC containing an in situ β-phase, a stress-overshoot characteristic, observed in the BMG, is not presented, but elongation to failure is rather limited because the crystalline β-phase prevents the viscous flow of the amorphous phase. The different presence of the crystalline phases in the metallic glasses can differently affect the flow behavior of metallic glass in the supercooled liquid region.

The structural and electrical properties of lanthanum copper oxide were examined as a function of Sr addition. It was observed that the lanthanum oxide and copper oxide formed La2CuO4 with K2NiF4 structure when the powder mixture was heated at 800 °C in ambient pressure. Interestingly, the samples of Sr-doped (15∼25%) lanthanum copper oxides showed single perovskite-based phase after being heated at 800 °C. Without Sr addition, a single-perovskite phase of lanthanum copper oxide was observed only under the oxygen pressure as high as 65 kbar. The stabilization of perovskite structure in lanthanum copper oxide was effectively achieved by the addition of Sr. Based on the titration analysis and pertinent defect reactions, the enhancement of perovskite stability was due to the presence of trivalent copper ions that were created to balance the electrical charge of doping ion (SrLa′). With the increasing concentration of trivalent copper ions (or electron holes equivalently) in Sr-doped samples, lanthanum copper oxide also changed from a semiconductor to metallic conductor. When the Sr dopant exceeded its solubility limit of approximately 25% in the A-site sublattice, the Sr-rich second phases, La2SrCu2O6 and Cu2SrO3, appeared and suppressed the electronic conduction drastically.

A structural and morphological study of nanostructured gold thin films prepared by pulsed laser deposition in the presence of several inert background gases (Ar, He, and N2) and at various pressures (from 10 mTorr to 1 Torr) and target-to-substrate distances (from 1 to 10 cm) is presented. Structural and morphological analyses were undertaken using semiquantitative x-ray diffraction, scanning tunneling microscopy, and transmission electron microscopy. For each set of deposition conditions, the kinetic energy of the neutral gold species [Au(I)] present in the plasma plume was determined by time-of-flight emission spectroscopy and used to characterize the plasma dynamics. It is shown that all films exhibit a transition from highly [111] oriented to polycrystalline as the Au(I) kinetic energy decreases. The polycrystalline phase ratio is close to 0% for Au(I) kinetic energy larger than approximately 3.0 eV/atom and approximately 86 ± 10% for Au(I) kinetic energy smaller than approximately 0.30 eV/atom, irrespective of the background gas atmosphere. The mean crystallite size of both phases and the mean roughness of the films also follow a unique relation with the Au(I) kinetic energy, independently of the nature of the background gas, and nanocrystalline films with crystallite size as small as 12 nm are obtained for Au(I) kinetic energy smaller than 0.3 eV/atom.

Lutetium nitride (LuN), an end member of a new quaternary system Si3N4–SiO2–Lu2O3–LuN, was synthesized by direct nitridation of a lutetium metal. The nitridation extent of the lutetium ingot (10 × 5 × 2 mm) reached about 97% by heating at 1600 °C for 8 h with an applied N2 pressure of 0.92 MPa; the initial shape of the bulk metal was maintained in the course of nitridation. The resulting nitrided lutetium possessed a moderately low oxygen content (∼0.7 wt%), which enables the preparation of uncharacterized high nitrogen-containing phases in the Lu–Si–O–N system.