Ion implantation is used to fabricate waveguides in LiNbO3;. We have implanted a variety of ions into LiNbO3; at energies from 100 to 300 keV and have been able to profile their depth distributions by secondary ion mass spectrometry. We report here their depth distributions and range parameters determined from Pearson IV fitting.

The fluorite-related oxides have many uses in applied materials science and they present an excellent subject for study in solid state science. They exhibit examples of nonstoichiometric phases of wide composition range and series of ordered intermediate phases. Some details of the ordering of oxygen vacancies in the nonstoichiometric fluorite-related phases of the rare earth oxides are presented, including imaging of the process at high resolution in the electron microscope. Other highresolution studies of the ordered intermediate phases have revealed the structural principles that relate members of the homologous series RnO2n−2 Other ordered structures not belonging to the series are also discussed and the whole related to the zirconia and hafnia systems stabilized by calcia and yttria.

Two refractory material systems show promise for efficient energy conversion at high temperatures (>1000 K): the rare-earth chalcogenides and the boron-rich borides. The electronic and thermal transport properties of these two systems are compared and discussed.

The electrical conduction mechanisms in MgO:Ni with Pt electrodes at 1473 K are studied over electric field ranges up to ∼10 kV/cm. The current transients induced by pulsed changes of the applied voltage as well as transient shortcircuit currents have been measured and analyzed to yield two electron hole recombination lifetimes of 10 and 250 s. The main features of the results are consistent with the double injection model of the electrical breakdown of MgO at high temperatures.

The electrical conductivity of MgO:nAl2O3spinel has been measured for 1 < n < 3.6 for temperatures between 500 and 1400°C. The results for nonstoichiometric spinel are significantly different from those of stoichiometric material. Spinel with n up to 2 was found to be stable at temperatures above 1000°C, whereas, MgO:3.6Al2O3 exhibited multiple indications of instability and disproportionation.

In all previous studies of tungsten oxide films it has been implicitly assumed that the film is uniform except for grain boundaries in polycrystalline films. In this study we show that amorphous tungsten oxide thin films contain highly anisotropic void networks which not only dominate their physical structure but also control their electrochromic behaviour. The void network structure is controlled primarily through ion bombardment of the growing film during deposition while the film stoichiometry HyWO3−x is controlled by the reactive sputtering processes of tungsten in Ar/O2/H2 atmospheres. The evolutionary growth model of physical structure was studied in detail by both transmission and scanning electron microscopy. On the basis of physical structure-property correlations we are able to consistently explain the basic electrochromic characteristics and chemical stability of the films. Such information leads to better understanding of the problems and limitations inherent in thin film electrochromic devices.

Cathodoluminescence of thermochemically reduced MgO crystals has been studied in the scanning electron microscope. Two peaks at around 3.0eV (410nm) and 2.4eV (520nm) have been detected. The intensity evolution of these two peaks with temperature and electron beam irradiation has been recorded. The results are analyzed on the basis of emission from anion vacancies (F and F+ centers)

Thermochemical reduction at high temperature of MgO and CaO single crystals introduces both anion vacancies, with absorption in the ultraviolet, and substitutional H− ions, with local mode absorptions near 1000 cm−1. The source of the hydrogen is water in the starting material. H− ions strongly influence the photoluminescence and thermoluminescence of the samples and enable F center luminescence to be excited at low temperature by low energy, E<1.8 eV, radiation. The long-lived luminescence of anion vacancies in these samples is accompanied by photoconductivity and a large dark current which increases as the concentration of H− ions increases. The activation energy for release of electrons from H= ions can be calculated from the temperature dependence of the F center luminescence decay.

The feasibility of slip casting monosized ceramic powders has been investigated using colloidal (spherical) SiO2 particles. Pertinent aspects of powder syntheses, particle characteristics, and slip preparation are discussed. Processing variables affecting the permeability of the cast compact to fluid flow are discussed in relation to forming cast bodies with near ideal (ordered) particle packing.

Powdered compacts that do not have periodic, particulate arrangements exhibit nonperiodic density variations and are, by definition, agglomerated. The void phase in the compact can be separated into pores. The pore coordination number distribution and the critical coordinated number (Rc) governs the volume fraction of pores that can spontaneously disappear by diffusion, and therefore, the compact's sinterability. The pore coordination number distribution is favorably influenced by increasing the compact's initial density and decreasing the size of the multiple particle packing unit (for example, agglomerate size). During heating the pore coordination number distribution is unfavorably shifted by local sintering, which is produced by the spontaneous disappearance of pores with favorable coordination numbers (R < Rc). Local densification produces a dense, polycrystalline skefetal network. Grain growth during densification, supported by dense regions, favorably alters the coordination number of pores within the skeletal network and improves sinterability. The configuration and microstructure of the dense, skeletal network will control its compliance to deformation by either effective or applied (hot pressing) compressive stresses. Deformation of the dense, skeletal network will improve the coordination number distribution and thus sinterability. From this thinking, one concludes that the ideal situation requires either a periodic particle arrangement (which requires monodispersed powders), or lacking this arrangement, alterations in surface chemistry (or structure) such that Rc → ∞.

Hydrothermal preparation is one of the methods to make fine ceramic powders. There are: (1) hydrothermal oxidation, (2) hydrothermal precipitation, (3) hydrothermal synthesis, (4) hydrothermal decomposition, (5) hydrothermal crystallization, etc. Starting materials for hydrothermal oxidation is mainly metal. Reaction between metal and high temperature-high pressure solution occurs to form oxide. Therefore, starting materials for very fine powders are: (1) metal powders or chips, (2) gel, solutions, etc., (3) oxides and solutions, (4) solids, and (5) hydrous material. This paper describes hydrothermal crystallization and oxidation. Fine powders of ZrO2, Al2O3, HfO2, and Al2O3-ZrO2 are described.

Sintered bodies are also able to get under hydrothermal conditions with reactions. Hydrothermal reaction sintered bodies of iron oxides, Cr2O3, ZrO2 and HfO2 were obtained under 100 MPa above 1000°C with 1–5 μm grains.

Alumina rods doped with MgO have been sintered by rapid translation through three plasma devices, namely a microwave induced plasma, a hollow cathode discharge, and an RF induction coupled plasma. Rapid densification to high density and fine grain size was observed. Some similarities and significant differences existed among the different devices.

The structures of aluminum nitride and aluminum oxide powders have been modified by explosive shock treatment at pressures from 4 to 27 GPa. Shockinduced dislocations in AlN were apparently responsible for enhancement in hot pressing behavior. In Al2O3 an increase 3 to 4 times in densification rates after shocking resulted-from rapid sintering of aggregates in the powder.

The properties of glass and ceramic materials are largely determined by the types and distribution of bonds in the network structure. Since conventional methods of forming these materials by melting or sintering do not allow significant variations from the equilibrium conditions, the properties of these materials are generally fixed by the chemical composition and crystalline structure. Synthesis of these materials by chemical polymerization at low temperatures, on the other hand, permits significant modifications to the ultrastructure. These structural modifications in turn modify the material properties, without compositional alterations. In this presentation, further studies of structure-modifying parameters are discussed.

An Analytical Electron Microscopy investigation of TiB2 hot-pressed and pressureless sintered with Ni revealed the presence of Ni3B and tau intergranular phase, respectively. Convergent Beam Electron Diffraction (CBED) was used for crystal structure determination and compositions were determined by quantitative x-ray Energy Dispersive Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS). The phase analyses were compared with phase diagram data. An evaluation was also made of TiB2 hot pressed with Ni3Al. Quantitative EDS and EELS microanalysis indicated a Ni,Al type boride tau (Cr23C6 type) intergranular phase.

I present an assessment of the technological potential of shock wave consolidation of ceramic powders as a technique for producing well-bonded, uniform, crack-free monoliths. Current compaction methods are briefly reviewed and the characteristics of the consolidated material are presented. The shock and release histories experienced by powder compacts in simple compaction assemblies are complex and I conclude that such simple assemblies are unlikely to yield structurally sound bodies. Control of the stress history over the entire loading cycle is necessary if the tensile stresses which develop during release are to be reduced to acceptable levels. Such exacting control is difficult to achieve, and becomes increasingly difficult as the peak stresses are increased. The powder must therefore be sufficiently plastic at moderate stresses to permit densification and bonding of the compact without destruction of the compact during release. Not all ceramic powders will satisfy this criterion. Local microstructural modification, including interfacial melting, is limited by the fine particle sizes and large surface areas of many ceramic powders. Production of cohesive, crack-free bodies thus depends upon a complex interplay between shock history, material properties, and powder characteristics which is poorly understood. I conclude that the technology of dynamic consolidation of ceramic powders will be difficult to develop and will have limited applications.

Pure-AIN powder compacts have been fabricated by isostatic pressing and impact forming in the pressurs range of 1.5 ˜ 5.5 GPa. The density of these compacts was in the range of 70 ˜ 90% of the theoretical. The mean particle size was reduced from 20 μm to a few micron meters depending on compaction pressures. The density changes observed after sintering at temperatures above 1,600°C were independent of initial starting densities. A similar shrinkage was observed when residual strains were eliminated by annealing at 1,550°C for 30 min. Micro-structures of the sintered specimens showed a mixed region of either extensive grain growth or little growth.

Submicron particle sizing is complex, requiring careful interpretation of distribution data. Information gathered from laboratory use of a sedimentometer and a light scattering system are discussed in terms of strengths and weaknesses.

Powders of AlN, TiC and TiB2 have been subjected to controlled shock loading with peak pressures in the samples between 14 to 27 GPa and preserved for post-shock study. Broadened x-ray diffraction peak profiles are analyzed by a simplified method and show increases in residual lattice strain and small decreases in crystallite size. Strain values range from 10−5 to 10−4 for TiB2 and to values larger than 10−3 for TiC and AlN.

The annealing behavior of shock modified rutile (TiO2) powder was studied by transmission electron microscopy, x-ray line broadening, and electron spin resonance. Specimens were examined in the as-received and as-shocked conditions, and in shocked and annealed conditions after one hour at 475° or 1000°C. The dislocations generated by the shock treatment were found to persist essentially unaltered through the 475°C anneal. Substantial recovery was observed after the 1000°C anneal.