Successful application of sol-gel, metalorganic decomposition, or hydrothermal routes to ceramic thin films depends on the mechanical integrity of the precursor film. Above a critical thickness, a precursor film will crack or decohere from the substrate during drying. The cracking and thickness of thin metalorganic precursor films were simultaneously observed during drying using a standard optical microscope. Isochromatic color fringes produced by interference of reflected white light were used to monitor film thickness. The critical film thickness was determined by the color fringe corresponding to the thickness at which propagating cracks terminated. As a demonstration of the technique, the critical thickness of titanium di(isopropoxide) bis(ethyl acetoacetate) films was measured, showing increased critical thickness with the addition of small amounts of an elastomeric polymer.

Nanosized MnFe2O4 phase with diameters in the range 13.7 to 100 nm were produced by calcination and sintering treatments in the system zNb2O5 · (50 – z)MnO · 50Fe2O3 with z having values between 0 and 20. Nb5+ ions are believed to give rise to vacancies in the Mn2+ sites, which break up the coupling of ferrimagnetically active oxygen polyhedra. The Curie temperature decreases as the size of the MnFe2O4 phase is reduced. This is explained on the basis of a decrease in the number of exchange pairs of the type Mn2+–Fe3+. The coercivity increases with a decrease in the size of the ferrimagnetic phase. This is believed to arise due to a decrease in saturation magnetization as the size of the MnFeO4 phase is reduced.

This paper focuses on understanding stress development in CuNi42Mn1 thin films during annealing in Ar. In addition to stress-temperature measurements, resistance-temperature investigations and chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, x-ray diffraction, and atomic force microscopy were also carried out. The films are polycrystalline with a grain size of 20 nm up to 450 °C. To explain the stress evolution above 120 °C, atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Grain-boundary relaxation was found to be the dominating process up to 250–300 °C. A sharp transition from compressive to tensile stress between 300 and 380 °C is explained by the formation of a NiO surface layer due to reaction with the remaining oxygen in the Ar atmosphere. This oxidation is masking the inherent structural relaxation above 300 °C.

In order to clarify inconsistencies in the literature and to verify assumed ternary solubilities, the phase equilibria in the Y2O3–Al2O3 –SiO2 system at 1600, 1400, and 1300 °C were experimentally determined using x-ray diffraction (XRD), scanning electron microscope with attached energy-dispersive detector system (SEM-EDX), and electron probe microanalyzer (EPMA). Six quasibinary phases were observed: Y4Al2O9 (YAM), YAlO3 (YAP), Y3Al5O12 (YAG), Y2SiO5, Y2Si2O7 (C and D modifications), and ˜3Al2O3· 2SiO2 (mullite). Y4Al2O9 forms an extended ternary solid solution with the formula Y4Al2(1-x)Si2xO9+x (x = 0 2 ˜0.31). The lowest ternary eutectic temperature was determined at 1371 ± 5 °C by high-temperature differential scanning calorimetry (DSC). The results were compared with previous data available for the Y2O3–Al2O3 –SiO2 system and with data for other RE2O3–Al2O3 –SiO2 (RE = rare earth element) systems.

The phase stability of Ni–Al clusters of nanometer size was studied by using the embedded atom model and Monte Carlo simulation techniques. For temperatures of 500 and 1000 K and for a range of compositions below 70 at.% Al, the equilibrium structures of the system were determined and compared with the bulk results. We found that the bulk NiAl (B2) and Ni3Al (L12) phases were stable phases in the nanoparticle system; however, for deviations from ideal composition, the analysis revealed that, because of the surface effect, the composition of the clusters was not uniform. There was a core region in which the structure was ordered, B2 or L12, with a composition very close to the ideal, and a chemically disordered mantle region that allocated the deviations from ideal stoichiometries; in this way, a larger phase field appeared, indicating trends similar to those found in experiments on nanocrystalline Ni–Al powder [S.K. Pabi and B.S. Murty, Mater. Sci. Eng. A214, 146 (1996)]. For concentrations between 37 and 51 at.% Al, an intermediate phase, similar to the tetragonal L10 martensite, appeared.

The effect of lower valent substituents on the stability of the antiferroelectric phase of lead zirconate was studied by dielectric spectroscopy, Sawyer–Tower polarization methods, and electron diffraction techniques. The stability of an intermediate ferroelectric phase region was found to be enhanced with increasing lower valent substitution concentration. The influences of substituents of different ionic size and valence on the stabilization of the intermediate ferroelectric phase were differentiated. In general, lower valent substituents, such as K+ and Fe3+ affected antiferroelectric phase stability more significantly than higher valent ones.

Epitaxial Pb(ZrxTi1−x)O3 (x = 0.0−0.32) ferroelectric thin films of 500 nm thickness were grown on MgO(001) single crystal substrates by in situ rf magnetron sputtering, and evolution of their domain structures is characterized by employing various x-ray diffraction techniques. X-ray θ-2θ scan showed the films were grown highly c-axis oriented with a tetragonal perovskite structure. 90° domain configuration was investigated using the x-ray rocking curve analysis for PZT 100 peaks in two different Φphi; angles. The rocking curve analysis showed that the degree of c-axis orientation and the crystalline quality of the films were improved continuously with increasing Zr concentration. The c-domain abundance as a function of Zr concentration was quantified using the x-ray rocking curves of PZT 001 and 100, taking account of structural factors and Lorentz-polarization factors. High temperature x-ray technique was also employed to quantify the domain structure as a function of temperature during cooling after reheating the samples to 650 °C. During the cooling process, c-domain abundance was found to increase continuously while the crystalline quality of the films was deteriorated below the Curie temperature. The results led us to conclude that the transformation strain of the film at and below the Curie temperature plays a significant role in the final domain structure and abundance of epitaxial PZT thin films.

We successfully deposited high-quality TiN films on c-plane sapphire by using the pulsed laser deposition technique. TiN grew on sapphire with two in-plane epitaxial relationships: (111)TiN//(0001)sapphire and [101]TiN//[1100]sapphire or (111)TiN// (0001)sapphire and [101]TiN//[1100]sapphire. The TiN unit cell showed a ±30° in-plane rotation for sapphire. The misfit between the TiN film and the sapphire substrate was calculated by using the near coincidence site lattice approach. The deposited films were analyzed by x-ray diffraction, transmission electron microscopy, atomic force microscopy, Rutherford backscattering or channeling spectrometry, electrical, and spectrophotometric measurements. The dependence of the film's crystalline quality on the deposition temperature has been investigated. The full width half-maximum of the rocking curve of the TiN 111 peak was 0.2–0.3°. The minimum ion channeling was 5%, and the room temperature resistivity was as low as 13 μω cm.

Nanocrystalline manganese oxide powders have been prepared at 25 °C by precipitation from Mn(NO3)2 aqueous solution. The presence and addition sequence of H2O2 significantly influence particle characteristics of the resulting manganese oxides, including crystal structure, particle size and morphology, and surface area, depending upon molar ratio of H2O2 with respect to Mn. The precipitation from preoxidized manganese solution by H2O2 results in flakelike-shaped amorphous hydrous manganese oxide (MnO2xH2O). In the absence of H2O2, on the other hand, amorphous Mn(OH)2 is obtained, and a part of Mn(OH)2 subsequently transforms into crystalline Mn3O4 by oxidation in air. Relative population of amorphous Mn(OH)2 decreases by dissolution when post-treated with H2O2. At Mn:H2O2 = 1:4, the well-defined 16-nm-sized nanocrystalline Mn3O4 with homogenous particle morphology is prepared. The treatment with excess H2O2, however, destroys crystalline Mn3O4 and leads to further oxidation of the aqueous manganese species. Under these conditions, a mixture of needlelike Mn2O3 and cubelike Mn3O4, including amorphous MnO2xH2O, is obtained.

We conducted hydrostatic compression and constant-stress-difference experiments, with and without an applied electric field, on poled, niobium-doped lead zirconate titanate ceramic. The objective was to quantify the effects of nonhydrostatic stress and electric field bias on electromechanical behavior of the ceramic during the ferroelectric, rhombohedral → antiferroelectric, orthorhombic phase transformation. Increasing stress difference (shear stress) decreases the mean stress at which the transformation occurs. Increasing shear stress also retards the rate of transformation, causing reductions in both the rate of charge release and peak voltage attained during depoling. Application of the electric field bias slightly increases the transformation pressure for poled ceramic. Previously, we showed that under nonhydrostatic stress, the transformation took place in unpoled ceramic when the maximum compressive stress equalled the hydrostatic pressure at which the transformation would otherwise occur. This simple stress criterion does not apply to poled ceramic. However, poled material has a preferred crystallographic orientation and mechanical anisotropy, whereas unpoled ceramic is isotropic. We present a qualitative model for the transformation under nonhydrostatic stress-related to that anisotropy, which resolves these seemingly disparate observations.

Second-harmonic generation of transparent glass-ceramics containing BaTiO3 crystalline phase was investigated using Maker fringe method. When 15BaO · 15TiO2 · 70TeO2 glass was heat-treated at 415 °C for 0.5–12 h, (101)- or (110)-oriented BaTiO3 crystals precipitated in the near-surface region. The resultant glass-ceramics exhibit second-harmonic generation. Variation of second-harmonic intensity with angle of incidence, i.e., the Maker fringe pattern changes drastically with an increase in heat treatment time and temperature. No second-harmonic signal was detected in glass-ceramics derived from 15SrO · 15TiO2 · 70TeO2 glass. These facts suggest that BaTiO3 crystal is responsible for the second-order nonlinear phenomenon, although its structure is closer to cubic than tetragonal according to x-ray diffraction measurements. In order to estimate second-order nonlinear optical coefficient d(2), Maker fringe patterns of the BaTiO3-containing glass-ceramics were analyzed. For the glass-ceramic after heat treatment for 0.5 h, d33 and thickness of BaTiO3-crystallized layer, L, are 3.65 pm/V and 3.43 μm, respectively. The value of second-order nonlinear optical coefficient is comparable to those of BaTiO3 films prepared via metalorganic chemical vapor deposition and pulsed-laser deposition. On the other hand, the glass-ceramic heat-treated for 12 h exhibits d15 = 0.31 pm/V and L = 300 μm. The thickness of the layer active in second-order nonlinearity evaluated from the Maker fringe pattern is coincident with the observation by scanning electron microscopy.

A vacuum infiltration process has been developed to fabricate the aluminum matrix composites reinforced with low volume fraction (<50 vol%) of SiCp. Generally, it is difficult to fabricate low volume fraction particulate composites by traditional infiltration processes because the particles always pack up to about 50 vol% in the preforms or compacts. In this study, the powder compacts were prepared of the well-mixed Ni-coated SiCp and pure aluminum powders and then were packed in quartz tubes. An aluminum alloy (Al–8.7% Si–2.6% Cu) with a composition similar to AA 380.0 was used to infiltrate these compacts. Experimental results showed that the infiltration temperature of 640 °C is favorable for the fabrication of these composites. Infiltration behavior, microstructure, nickel distribution, bending test, and fractography of the composites were investigated.

The change in ultrasonic nonlinear property of a titanium alloy subjected to cyclic loading has been studied, with an objective to develop a new characterization methodology for quantifying the level of damage in the material undergoing fatigue. In order to determine the degree of nonlinearity, the ultrasonic second harmonic generation technique has been used. The second harmonic signal was monitored during the fatigue process, and a substantial increase in the second harmonic amplitude (180% increase in nonlinear factor) was observed. This indicates that the second harmonic signal is very sensitive to the microstructural changes in the material caused by fatigue.

PbTiO3 (PT) thin films have been deposited by sol-gel on Pt/Si, SiO2/Si, Pt/Ti/SiO2/Si, and Ti/Pt/Ti/SiO2/Si and annealed for 45 min in the 400–670 °C range. Analysis by x-ray diffraction (XRD) and spectroscopic ellipsometry shows that the Ti overlayer promotes early crystallization in the tetragonal perovskite phase, reducing the presence of a second phase, tentatively identified as pyrochlore, starting by 450 %C. The refractive index and extinction coefficient (n, k) of the PT film increase rapidly with the sintering temperature in the range of 450–570 °C and saturate by 570 °C to values of n varying from 2.4 to 2.9, and k from 0.03 to 0.3, over the 1.65–2.95 eV range. Most of the increase of n is related to thin film densification.

PbTiO3 powders and heteroepitaxial thin films were produced by the hydrothermal method at 110–200 °C using different bases (Na–, K–, Rb–, Cs–, TMA–, and TBA–OH). Microstructural characterization showed that the tetragonal perovskite films were epitaxial on the SrTiO3 substrates, with a c-axis out-of-plane orientation. Sequential growth experiments showed that the growth initiates by the formation of 100 nm {100} faceted PbTiO3 islands followed by coalescence. Small cation bases (Na–, K–, Rb–OH) produced 1.5-μm {100} faceted blocky powders, whereas larger cation bases (Cs–, TMA–, and TBA–OH) formed fewer 500-nm interpenetrating platelets. Nuclear magnetic resonance results showed cation incorporation in the perovskite structure with local disorder on the Pb sites increasing cation size.

A modified route, based on calcined MgO, Ta2O5, BaCO3, and ZrO2, was developed and used for preparation of barium magnesium tantalate (BMT) and barium zirconate (BZ)-doped BMT ceramics (BZ-BMT). The dielectric constant for BMT ceramics sintered at 1600 °C for 2 h was 24.9 at 7.28 GHz. The average long-range ordering parameter for undoped BMT ceramics was 0.81 ± 0.03 and the coresponding average quality factor and resonant frequench product (Qd · fo) was 147,000 ± 3800 GHz. A significant level of B-site long-range cation disorder was introduced as a result of BZ doping of BMT ceramics. The average ordering parameters for 3 and 4 mol% BZ-doped BMT were found to be 0.69 ± 0.06 and 0.49 ± 0.13, respectively. The decrease in ordering parameters did not lead to a dramatic decrease in the corresponding average quality factors of 3 mol% BZ-BMT (Qd · fo = 127,000 ±3800 GHz) and 4 mol% BZ-BMT (Qd · fo = 139,000 ± 4200 GHz). The results suggest that the B-site cation ordering is not a primary factor that influences the observed microwave loss in BMT ceramics. The influence of atomic level point defects, induced from raw material impurities, processing, etc., may be more important in controlling the quality factor of BMT ceramics.

The formation of barium hexaferrite from stoichiometric mixtures of BaCO3 and Fe2O3 has been investigated by means of differential thermal analysis and thermogravimetry, x-ray diffraction, and transmission electron microscopy–energy dispersive spectrometry. The first step, which implies decarbonatation and monoferrite formation, includes the formation of various intermediate compounds, which are formed at contact points between BaCO3 and Fe2O3 grains, and implies diffusion of both species. In the second step, barium hexaferrite is formed at interfaces between monoferrite and iron oxide mainly by diffusion of barium through the BF6 lattice into the hematite lattice. This exothermic reaction process leads to nonagglomerated pseudohexagonal platelets with an average particle size very close to the one of the starting powder mixture (∼1 μm).

The difference of domain switching amount of 3 mol% R2O3−ZrO2 (R = Yb, Y, Dy, Gd, Eu, Sm) pseudo-single crystals with additive cation species was investigated from the microstructural aspect. The switching amount of Yb, Y, Dy, and Gd substituted ZrO2 was three times higher than that of Eu and Sm. The amount corresponded to the volume fraction of the t′-phase, and it indicated that phase separation proceeded, especially in Eu and Sm substituted ZrO2.

Stoichiometric CaAl2Si2O8 gels prepared by the Pechini process crystallize to triclinic anorthite via an intermediate, previously unknown pseudohexagonal phase. Hydrothermal treatment of this pseudohexagonal phase at 350 °C transforms it to hexagonal anorthite. These combined processes produce the hexagonal phase via a low-temperature, chemical route in contrast to the conventional high-temperature melting and crystallization method. Powder x-ray diffraction data and nuclear magnetic resonance (NMR) spectra of the hexagonal anorthite agree well with the published structure. They indicate a high degree of tetrahedral Si/Al ordering within the layers, but long-range disorder in the average structure due to (001) stacking faults present between the layers.

This paper describes the microstructural characterization, using transmission electron microscopy (TEM), of the solid-state, diffusion-bonded interfaces generated in a SiC whisker-reinforced, aluminum composite. Diffusion bonding was carried out using an aluminum-lithium alloy as the bonding interlayer. Two kinds of bonded interface were studied: those generated between the composite matrix and the metallic interlayer (metallic-metallic) and other ceramic-metallic interfaces formed between the interlayer and the SiC whiskers. The first showed the formation of zones of recrystallization across the original bond interface, and the second generally presented a high degree of continuity without the formation of interface reaction layers between the SiC whiskers and the interlayer. However, the formation of a degradation oxide layer was detected in some of the whisker/interlayer diffusion bonds. Its presence is due to the reaction between the alloying elements of the Al–Li interlayer and the SiO2 layer which surround some of the whiskers of the parent composite.