Phase equilibria and dielectric properties were analyzed for selected compositions in both LaCa0.5Zr0.5O3–CaTiO3 (LCZ-CT) and LaCa0.5Zr0.5O3–SrTiO3 (LCZ–ST) systems using x-ray powder diffraction and transmission electron microscopy. The end-member LaCa0.5Zr0.5O3 does not occur as a single phase but rather as a mixture of a perovskite-type phase with approximate composition La0.94Ca0.53Zr0.53O3 plus a minor amount of La2O3. This perovskite phase exhibited a combination of 1:1 ordering of Ca and Zr on the B-sites and octahedral tilting. In the (1 – x)LCZ– xCT system, the compositions x = 1/3 and x = 1/2 yielded single phases with perovskite-like structures featuring similar 1:1 B-site ordering superimposed onto octahedral tilting. The x = 1/2 composition in the LCZ–ST system resides in a two-phase field and contains a major perovskite phase and La2O3; the B-cations in the perovskite phase remain disordered at all temperatures. The approximate boundaries of perovskite-like phase fields in the La2O3–ATiO3–CaZrO3 (A = Ca, Sr) systems were outlined, as well as a schematic diagram for perovskite B-cation ordering transitions in the LCZ–CT system. The dielectric properties of the compositions investigated were measured at microwave frequencies and were correlated with the observed structural behavior.

The crystal structure of Bi2Zn2/3Nb4/3O7 was determined using a combination of electron, x-ray, and neutron powder diffraction. The compound crystallizes with a monoclinic zirconolite-like structure [C2/c (No.15) space group, a = 13.1037(9) Å, b = 7.6735(3) Å, c = 12.1584(6) Å, β = 101.318(5)°]. According to structural refinement using neutron diffraction data, Nb preferentially occupies six-fold coordinated sites in octahedral sheets parallel to the (001) planes, while Zn is statistically distributed between two half-occupied (5 + 1)-fold coordinated sites near the centers of six-membered rings of [Nb(Zn)O6] octahedra. The Nb/Zn cation layers alternate along the c-axis with Bi-layers, in which Bi cations occupy both eight- and seven-fold coordinated sites. The eight-fold coordinated Bi atoms exhibited strongly anisotropic thermal displacements with an abnormally large component directed approximately along the c-axis (normal to the octahedral layers).

Tuning the temperature coefficient of resonant frequency (τf) in microwave dielectrics has been attributed to two main mechanisms: (i) dilution of the average ionic polarizability; (ii) the onset of an octahedral tilt transition above room temperature. The contributions of each mechanism have been isolated using ceramics in the Srn+1TinO3n+1, SrxCa1−x)3Ti2O7, and (SrxCa1−x)TiO3 series. In the Srn+1TinO3n+1 series, relative permittivity (εr) and τf are linearly proportional over a broad range of values, 100–37 and 800–140 ppm/°C, n = 4 and 1, respectively. No structural phase transitions occur on cooling from the prototype symmetry, and the mechanism of tuning is attributed solely to dilution of the average ionic polarizability as the SrO:SrTiO3 ratio increases. Exchanging Ca for Sr in the (SrxCa1−x)3Ti2O7 series resulted in an 80% reduction in the magnitude of τf from +320 to +50 ppm/°C but only 21% in permittivity (58 to 46). The effect was nonlinear and attributed primarily to the onset of a phase transition involving rotations of the octahedra on cooling. Superlattice reflections associated with the octahedral tilt transition have been identified.

The mechanical properties of WC–SiC thin films deposited by dual radio frequency magnetron sputtering were investigated. The films were characterized by x-ray photoelectron spectroscopy, x-ray diffraction (XRD), and transmission electron microscopy (TEM) to evaluate the details of the microstructure and degree of amorphization. The results indicate that small additions of SiC (<25%) can significantly increase hardness compared to a pure WC film, but higher SiC contents do not strongly affect hardness. XRD studies show the SiC had a disordering effect. TEM results showed that WC films had coarse porous structure, but films with a low silicon carbide content (approximately 10 to 25 at%) had a denser nanocrystalline structure. Samples with greater than 25% SiC were amorphous. The initial hardness increase at lower SiC contents correlated well with the observed densification, but the transition to an amorphous structure did not strongly affect hardness.

Macroscopic residual stresses in Al2O3/Al plates of graded composition were determined experimentally and by the finite element method (FEM). Experimental stress data were determined by sawing a notch in the plates and measuring displacements by Moiré interferometry. Residual stresses were calculated from the displacements using the weight function method. Experimentally determined stresses agreed with FEM data only if measured thermomechanical properties for the different compositions were used for finite element calculations.

Template-directed co-condensation was used to synthesize phenyl-modified MSU-1 and bi-functionalized MSU-1 silica containing binary moieties of covalently linked phenyl along with methyl or ureidopropyl [H2NCONH(CH2)3]. The texture properties of these materials from x-ray diffraction, Fourier transform infrared, nuclear magnetic resonance, scanning electron microscopy, high-resolution transmission electron microscopy, N2 adsorption, thermogravimetric analysis data, varied with the type of alkoxylsilane precursor and the amount of organosiloxane in the mixture. Small-angle x-ray scattering results, for the as-synthesized and surfactant-extracted organo-modified MSU-X, showed that the templates remaining in the mesostructures gave positive deviation from Porod's law while the incorporated organic groups led to a negative deviation, which formed an interfacial layer between the pore and silica matrix.

Superplastic deformation was realized on NiAl and NiAl-based alloys prepared by both common casting and directional solidification. Directionally solidified NiAl–27Fe–3Nb alloy as well as conventionally cast NiAl, NiAl–25Cr, NiAl–9Mo, NiAl–20Fe–Y.Ce, and NiAl–30Fe–Y alloys exhibited typical deformation characteristics shown in conventionally superplastic materials. NiAl and NiAl-based alloys could be divided into three categories depending on their different superplastic behavior: finely grained structure (NiAl–9Mo, NiAl–25Cr, NiAl–20.4Fe–Y.Ce, NiAl–30Fe–Y), coarsely grained structure (NiAl), and columnar structure (NiAl–27Fe–3Nb). The corresponding deformation mechanisms for fine-grained structure, coarsely grained structure, and columnar structure were grain boundary sliding or grain boundary sliding accompanied by dynamic recrystallization, dynamic recovery and recrystallization, and intragrain dislocation slip, respectively.

The structure of ceramic Ba4.5Nd9Ti18O54 was investigated by synchrotron x-ray powder diffraction from 10 to 295 K. Reitveld refinement and Le Bail profile analysis were applied to the data. Based on an orthorhombic structure, unit cell parameters of a = 22.3479(3) Å, b = 7.6955(1) Å, and c = 12.2021(2) Å were obtained at room temperature and a = 22.3367(5) Å, b = 7.6738(1) Å, and c = 12.1842(3) Å at 10 K. No evidence was found for any major structural change from 10 to 295 K. Within the tungsten bronze framework the two pentagonal channels were fully occupied by Ba; the remaining Ba atoms shared the rhombic channels with Nd. Thermal expansion of the unit cell was found to be anisotropic. The largest expansion occurs along the b cell edge, and the least along the a cell edge. It is proposed that the anisotropy is due to enhanced bending of the TiO6 polyhedra chains along the b direction.

InGaN-based optoelectronics were integrated with dissimilar substrate materials using a novel thin-film laser lift-off (LLO) process. The LLO process was employed to integrate InGaN-based laser diodes (LDs) with Cu and diamond substrates. Separation of InGaN-based thin-film devices from their typical sapphire growth substrates was accomplished using a pulsed excimer laser in the ultraviolet regime incident through the transparent substrate. Characterization of the LDs before and after the sapphire substrate removal revealed no measurable degradation in device performance. Reduced threshold currents and increased differential quantum efficiences were measured for LDs on Cu due to a 50% reduction of the thermal impedence. Light output for LDs on Cu was two times greater than comparable LDs on sapphire with a maximum output of 100 mW. Increased light output for LDs on diamond was also measured with a maximum output of 80 mW.

The cathodic deposition of iron–cobalt alloys inside the pores of anodically formed nanoporous silicon (PS) from p-type Si substrate is investigated with respect to the electrolyte composition. The samples were characterized by scanning electron microscopy, energy dispersive spectrometry, Auger electron spectroscopy, and Fourier transform infrared spectroscopy. Results showed that the nucleation of pure cobalt started at the bottom of the pores and the nucleation of pure iron occurred all over the pore walls, leading to a preferential deposition on top surface of the porous layer. Nevertheless, a low concentration of Co2+ ions (5 at.%) in the electrolyte drastically improved the penetration of iron into the pores. As a result, a good filling of the pores with Co metal as well as with Fe–Co alloys was achieved. It was also shown that the deposition process oxidizes the structure mainly at the pore walls. The results of our investigation indicate that the mechanisms occurring during the electrodeposition of metals on porous p-type silicon substrates are completely different depending on the kind of electrolyte used: pure iron-based electrolyte or cobalt-based solutions. A complete understanding of the deposition process requires further analyses of the carrier transport in PS and of the charge exchange at the Si/electrolyte and PS/electrolyte interfaces. These new results involving the deposition of iron-group materials into porous p-type silicon are useful for future silicon technologies.

Strain rate is an important factor in plastic deformation because it determines the constitutive behavior of rate sensitive materials, e.g., dislocation density and flow stress evolution, deformation heat generation, etc. In the present study, the strain rate of workpiece materials during equal-channel angular pressing (ECAP) was evaluated by a geometric approach. The results were compared to those of the finite element analyses of a model ideally plastic material with various mesh sizes. The derived equation for strain rate is in reasonably good agreement with the results of the finite element method. The effects of the die geometry (a channel angle and a corner angle) were investigated. The strain rate during ECAP increases with punch speed and decreases with die channel angle, die corner angle, and the width of the workpiece. The relation obtained can be used for analytical calculations of the deformation, thermal, and microstructural evolution behavior of materials during ECAP. In particular, the size of the deforming zone and the effect of the finite element size are discussed.

Ferroelectric lead lanthanum gadolinium zirconium titanate (PLGZT) thin films were prepared by the sol-gel spin coating technique. Three-step preannealing heat treatment was employed to prepare crack-free films. Various types of substrates, and the effects of the seed layer and annealing temperature on the perovskite crystallization were studied. Phase-pure perovskite crystallization was obtained by annealing the films on PbTiO3/Pt/Ti/Si substrates at 700 °C for 30 min. The Auger electron spectroscopy depth profile showed uniform elemental distribution along the thickness except the surface and interface regions. Dielectric constant and loss tangent at 10 kHz were 1000 and 0.06, respectively. Remanent polarization (Pr) and coercive field (Ec) were 11.8 μC/cm2 and 71 kV/cm, respectively. The direct band gap energy was 3.55 eV for the amorphous films. The refractive index and extinction coefficient at 610 nm for amorphous PLGZT films were 2.14 and 0.0028, respectively. The dispersion of the refractive index was interpreted in terms of a single electronic oscillator at 6.06 eV.

The results of the development and characterization of a new relaxor ceramic with nominal composition (x)Pb2(In,Nb)O6(1 − x)Pb(Mg1/3Nb2/3)O3 solid solution with x = 0.4 are reported. The structural characteristics, including the long-range and short-range order, forbidden reflections, and the existence of mixed ordering, were studied by transmission electron microscopy. The most prominent microstructural feature of this compound, which has composition variations in the micro- and nano-regions, was investigated. The presence of the pyrochlore phase and the complex arrangement of inclusions that originate from processing are illustrated. The electrical characteristics of the compound including pyroelectric, piezoelectric, electrostrictive and hysteresis properties are reported. Notable properties of the compound include a reduced hysteresis loop and nonlinear behavior at high field.

The effects of IrO2/Pt layered hybrid bottom and/or top electrode structures on the leakage current density versus voltage (J–V), polarization versus voltage (P–V), ferroelectric imprint, and fatigue properties of chemical-solution-derived Pb(ZrxTi1−x)O3 (PZT, Zr/Ti = 35/65) thin films were investigated. The best P–V and J–V performances were obtained from a capacitor with nonhybrid electrodes (Pt/PZT/Pt capacitor). However, the poor fatigue performance of the capacitor required the adoption of hybrid electrode structures. A thin IrO2 layer, as thin as 6 nm, which was inserted between top Pt electrode and PZT layer was sufficient for improving the fatigue performance without any degradation of the other ferroelectric properties. However, the same layer adopted on the bottom Pt electrode was not effective in improving the fatigue performance with degradation in P–V and J–V properties. This was ascribed to IrO2 layer dissolution into the PZT layer during the crystallization annealing of the PZT thin film. A thicker IrO2 layer resulted in more serious degradation.

The piezoelectric and dielectric properties of Pb(Zn1/3Nb2/3)O3 (PZN)-based ceramics were investigated. The perovskite structure of PZN ceramics was stabilized by the addition of Pb(Zn0.47Ti0.53)O3 (PZT). The highest piezoelectric properties were observed for the composition of 0.5PZN–0.5PZT, which lies on the two-phase zone of morphotropic phase boundary. For further improvements in electric properties, the specimens were thermally treated in a flowing O2 atmosphere at temperatures ranging from 860 to 1030 °C. The thermal treatment eliminated the PbO-rich amorphous intergranular layer by lead evaporation. As a result of this improvement in structure, the dielectric constant (ε′), the piezoelectric coefficient (d33), and the electromechanical coupling factor (kp), were enhanced markedly after thermal annealing at 960 °C for 8 h in an O2 atmosphere.

In this study, the interactions between transformation toughening and plastic stretching were investigated experimentally. Zirconia and metals, nickel or silver, were incorporated simultaneously into an alumina matrix. The extent of phase transformation of zirconia particles was enhanced due to the coexistence of soft metals. The ductility of nickel was also enhanced in the Al2O3–Ni–ZrO2 composites. However, the presence of zirconia particles at the alumina/silver interface reduced the ability of silver to deform plastically. Due to the interactions, the ratio of composite toughness to matrix toughness for the Al2O3–Ni–ZrO2 composite was higher than the product of the ratio of the composites containing only nickel and only zirconia.

The morphotropic phase boundary (MPB) composition that is characterized by the coexistence of rhombohedral and tetragonal phases in the Pb(Zn1/3Nb2/3)O3–BaTiO3– PbTiO3 system was modified by W-doping at the B site of a perovskite structural block. To maintain the electrical neutrality, creation of A-site vacancies was intentionally introduced in the formulation of the examined compositions. Incorporation of W ions was revealed to stabilize the tetragonal phase against the rhombohedral one, shifting the MPB toward the PZN-rich end at room temperature. High-temperature x-ray diffraction examination in combination with dielectric measurements discloses two successive phase transitions as a sample is cooled from high temperature, namely, paraelectric cubic to ferroelectric rhombohedral followed by ferroelectric rhombohedral to ferroelectric tetragonal. W addition appears to suppress the first transition while promoting the second one.

Potassium tantalate powders were hydrothermally synthesized at 100 to 200 °C in 4 to 15 M aqueous KOH solutions. A defect pyrochlore, Kta2O5(OH). nH2O (n ≈ 1.4), was obtained at 4 M KOH, but at 7–12 M KOH, this pyrochlore was gradually replaced by a defect perovskite as the stable phase. At 15 M KOH, there was no intermediate pyrochlore, only a defect perovskite, 0.85Ta0.92O2.43(OH)0.57 0.15H2O. Synthesis at higher KOH concentrations led to greater incorporation of protons in the perovskite structures. The potassium vacancies required for charge compensation of incorporated protons could accommodate water molecules in the perovskite structure.

Nanocomposite Ni/Al2O3 films were electrodeposited from a suspension of Al2O3 nanoparticles in aqueous nickel sulfamate solution. The volume fraction of particles incorporated increased with electrode rotation rate and decreased with deposition current density. The composition, microstructure, hardness, and magnetic properties of these nanocomposite films were characterized. The mechanical strengthening due to particle dispersion in the films was interpreted by considering an Orowan dislocation bowing mechanism. The coercivity of the films increased with increasing particle concentration in the film. The saturation magnetization showed a weak dependence on particle concentration.

A2B2O7 pyrochlore oxides are being considered as potential host materials for the immobilization of fission products. It is therefore important to establish the relative ability of these compounds to accommodate fission product ions. We address this issue by using computer simulations to predict the structures and relative equilibrium energies associated with solution of Sr2+ over an extensive compositional range. Results indicate that strontium is accommodated via substitution for A host cations with oxygen vacancy compensation. This results in a nonstoichiometric composition. Optimum compositions and defect clusters structures are identified by constructing contour energy maps.