X-cut potassium titanyl phosphate (KTiOPO4 or KTP) was implanted by multienergy MeV He+ implantation with a total dose of 2 × 1016 ions/cm2 at liquid nitrogen temperature. The energy and dose used are as follows: 3.3 MeV and 2 × 1015 ions/cm2, 3.2 MeV and 4 × 1015 ions/cm2, 3.1 MeV and 4 × 1015 ions/cm2, and 3.0 MeV and 1.0 × 1016 ions/cm2 to reduce tunneling effect. The 22 dark modes were measured by the isosceles prism coupling method. The 15 bright modes were observed after 250 °C, 60 min annealing. The result shows that the waveguide formation of KTiOPO4 implanted by MeV He+ is not strongly dependent on the cut direction, which is different from the waveguide formation of KTiOPO4 by ion exchange process.

In melt-processed YBa2Cu3O7−x (123) microstructures, often unreacted Y2BaCuO5 (211) particles are observed to be present in an inhomogeneous manner delineating distinguishable patterns. The presence of these patterns in 123 is more clearly observed in the case of low 211 volume concentration and also when the 211 particle size is small. The observed patterns are believed to be due to 211 particle segregation in 123 domains in specific planes during melt texture growth. In the present paper a software program is used to draw a three-dimensional visualization model to demonstrate a possible structure of 211 particle segregation in 123 domains and to explain the presence of observed patterns in the microstructures. The formation of such a 211 particle segregation is explained in the light of previously proposed 123 growth mechanisms.

In this paper, a comprehensive study of the microstructure and the whisker/matrix interface of a (MgO)w/BPSCCOhigh-temperature superconducting composite is reported. The bulk MgO-whisker reinforced HTS BPSCCO (2223) composite was fabricated using a recently developed solid-state processing method. The (MgO)w/BPSCCO composite has been demonstrated to possess excellent combined superconducting and mechanical properties. The favorable microstructure of the HTS BPSCCO (2223) matrix and the (MgO)w/BPSCCO interfacial properties are recognized to be the critical material parameters governing electric and mechanical performance of the HTS composite. Effects of detailed microstructure variables on superconducting properties of the composite are addressed, including the aspect ratio and the orientation of MgO whiskers, structure, and texturing of the BPSCCO matrix phase, and the (MgO)w/BPSCCO interfacial microchemistry. The results obtained reveal unique characteristics of the reinforcing MgO whiskers dispersion, distribution, and orientation in the HTS composites. The evolution of the microstructure and texture of thematrix BPSCCO grains has also been studied in the process of repeated hot-pressing and annealing heat treatment. The thermodynamic compatibility and microchemistry in the MgO whisker and BPSCCO interfaceare also examined.

A series of numerical calculations of convection were performed for the YBa2Cu3O7−x (Y123) single crystal growth by the modified pulling method (Solute Rich Liquid Crystal Pulling method; SRL-CP method). The finite-difference method was used to calculate the steady state of the axisymmetric two-dimensional incompressible viscous fluid system. The effect of the crystal rotation on the flow pattern and the temperature distribution in the melt was studied. An increase of the crystal diameter and/or the crystal rotation rate increased the strength of the forced convection in the melt, and as a result, the temperature at the crystal growth interface increased. These results were consistent with the experimental results.

The HOMO-LUMO gaps have been estimated in a graphite-like sp2 carbon network with a progressive increase in the fraction of sp3 carbons, taking into account several possible structural alternatives for each composition. The gap is shown to increase exponentially with the fraction of sp3 carbons. Accordingly, the gap in a diamond-like sp3 network decreases with the increase in the fraction of sp2 carbons.

A sol-gel process for preparing SnO2 monolith of high specific surface area and transparency from chloride solution is described. Without introducing any alkaline precipitating reagent to induce condensation, this new process employs tin chloride (or its hydrate), water, and, optionally, alcohols as the only process reagents. Spontaneous solution-to-sol and sol-to-gel transitions take place upon mixing these reagents under appropriate conditions, and the entire transition processes are carried out under acidic conditions (typically pH ≤ 4.0). The rate of condensation has been found to increase with decreasing SnCl4 concentration, which corresponds to decreasing solution acidity, and with increasing temperature. For fixed starting salt concentration and temperature, there exists an optimum amount of ethanol addition for the fastest condensation. Good performance of thus derived SnO2 monolith has been demonstrated in two applications, including catalytic oxidation and solid-state gas-sensing for carbon monoxide.

The defect structure of epitaxial, c-oriented Bi2Sr2Can−1CunO4+2n+δ (BSCCO) thin films grown by dc-sputtering and layer-by-layer MBE on SrTiO3 and LaAlO3 single crystal substrates was investigated by high-resolution transmission electron microscopy (HRTEM). Particular emphasis was put on the structure of the film/substrate interface. The films grown by dc-sputtering show a rather perfect structure involving a regular stacking of the unit cells. In spite of this regularity, there are many defects, such as twins, chemical stacking faults, and precipitates, as well as interfacial dislocations accommodating the film/substrate lattice misfit. The MBE-grown films contain twins and interfacial dislocations, but most prominent are precipitates of various size and rather high number density. Composition and structure of the precipitates were analyzed. Interfacial dislocations were found to be located in the films at a distance of up to 3 nm from the film/substrate interface. The experiments showed that the quality of the film/substrate interface in MBE-grown films is considerably higher with respect to smoothness, sharpness, and regularity, if the layer-by-layer MBE process starts with a Sr–O layer instead of a Bi–O layer. This observation is in correspondence to the observed interface structure of the dc-sputtered films, where the first film layer was a Sr–O layer, not a Bi–O layer, in spite of the films being sputtered from a composite target. A structure model of the Bi2Sr2Can−1CunO4+2n+δ/(100)SrTiO3 interface is proposed. The prolonged MBE process was shown to imply a chemical interaction between the SrTiO3 substrate and the growing film, resulting in the formation of Sr-rich phases in the near-interface substrate regions.

Films of Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 have been grown using Atomic-Layer-by-Layer Molecular Beam Epitaxy (ALL-MBE) on lattice-matched substrates. These materials have been combined with layers of closely related metastable compounds like Bi2Sr2Ca7Cu8O20 (2278) and rare-earth-doped compounds like Bi2Sr2DyxCa1–xCu2O8 (Dy: 2212) to form heterostructures with unique superconducting properties, including superconductor/insulator multilayers and tunnel junctions. Transmission electron microscopy (TEM) has been used to study the morphology and microstructure of these heterostructures. These TEM studies shed light on the physical properties of the films, and give insight into the growth mode of highly anisotropic solids like Bi2Sr2CaCu2O8.

Bulk single crystals of Y123 are required to clarify the superconductivity phenomena and develop electronic devices using unique superconductive properties. Only the Solute-Rich Liquid–Crystal Pulling (SRL-CP) method has succeeded in continuous growth of the Y123 single crystal. In this paper, we investigated the growth of Y123 single crystals under different temperature gradients in the solution in order to understand the growth mechanism of Y123. It was revealed that Y123 single crystals grow with a spiral growth mode, which is in good agreement with the BCF theory.

The addition of Y2BaCuO5 (211) particles to large grain melt textured YBa2Cu3O7–δ(Y123) has significantly improved the critical current density (Jc) of this material. Here, a systematic quantitative analysis on the effects of the 211 addition was performed on a microscopic scale with a systematic variation of the initial volume percent of 211. From the correlation between critical current measurements and quantitative microscopy of both (001) and (110) sections, a maximum value of Jc is observed, corresponding to a measured Y123 volume percent of 20% ± 3%. Accounting for the loss of liquid phase for the present processing, the corresponding optimum initial volume of 211 for the highest measured Jc is 40%. Further comparison between the weighted Jc and the true flux pinning force (Fp) also shows a maximum pinning force for an initial 211 addition of 40%. Although the weighted Jc starts to decrease with an initial 211 volume of above 40%, the pinning efficiency at higher magnetic fields (2–4 T) of the superconducting Y123 matrix was actually improved with an ever increasing 211 addition to at least 50%. Though an increasing addition of 211 is effective in producing efficient flux pinning sites in the Y123 matrix, percolation paths in the Y123 matrix become limited for supercurrent. Hence, a measured 211 volume corresponding to 80% 211 is proved to give the best possible critical current density. Furthermore, crack opening and crack spacing of the superficial cracks are found to decrease with an increasing 211 addition and with a decreasing 211 interparticle spacing. The penetration and surface length of each of these superficial cracks are hence reduced, which leads to a better electrical connectivity in the Y123 matrix.

The c-axis oriented YBa2Cu3O7−δ films grown on (001) yttria-stabilized cubic zirconia (YSZ) substrates often contain domains whose in-plane alignment is rotated approximately 9° from the cube-on-cube epitaxial relationship, in addition to the more commonly observed 0° and 45° in-plane rotations. We have investigated the origin of this ∼9° orientation using in situ electron diffraction during growth and ex situ 4-circle x-ray diffraction. Our results indicate that the ∼9° orientation provides the most favorable lattice match between the interfacial (110)-oriented BaZrO3 epitaxial reaction layer, which forms between YBa2Cu3O7−δ and the YSZ substrate. If epitaxy occurs directly between YBa2Cu3O7−δ and the YSZ substrate, i.e., before the BaZrO3 epitaxial reaction layer is formed, the 0° and 45° domains have the most favorable lattice match. However, growth conditions that favor the formation of the BaZrO3 reaction layer prior to the nucleation of YBa2Cu3O7−δ lead to an increase in ∼9° domains. The observed phenomenon, which results from epitaxial alignment between the diagonal of a square surface net and the diagonal of a rectangular surface net, is a general method for producing in-plane misorientations, and has also been observed for the heteroepitaxial growth of other materials, including (Ba, K)BiO3/LaAlO3. The YBa2Cu3O7−δ/YSZ case involves epitaxial alignment between [111]BaZrO3 and [110]YSZ, resulting in an expected in-plane rotation of 11.3° to 9.7° for fully commensurate and for fully relaxed (110)BaZrO3 on (001)YSZ, respectively.

A new semiempirical formula is developed for the hardness determination of the materials from depth sensing indentation tests. The indentation works measured both during loading and unloading periods are used in the evaluation. The values of the Meyer hardness calculated in this way agree well with those obtained by conventional optical observation, where this latter is possible. While the new hardness formula characterizes well the behavior of the conventional hardness number even for the ideally elastic material, the mean contact pressure generally used in hardness determination differs significantly from the conventional hardness number when the ideally elastic limiting case is being approached.

Rapidly quenched melt-spun ribbons of palladium-based borocarbides with large fractions of the superconducting phase (Tc > 20 K) have been obtained. Superconductivity in the Pd-based alloys seems to be metastable and exists only in the rapidly quenched state. Thus, while in the as-cast state the YPd2B2C ingot is found to be paramagnetic, the rapidly quenched ribbon superconducts and has a simple XRD pattern characteristic for a fcc lattice with a lattice parameter of 4.15 Å. A systematic study in an annealing sequence shows decay of the superconducting phase above 750 °C. The reduction in the integral intensities of XRD fcc peaks correlates well with the loss of the superconducting fraction on successive annealing. The recently reported tetragonal phase, attributed to the superconducting state in this system, is not found in any of our rapidly quenched samples. We present the phase diagrams indicating the optimum composition regimes for superconductivity in the Y–Ni–B–C and Y–Pd–B–C systems. From our magnetic data the values for the upper critical field Hc2(0), and the coherence length ξ(0) are estimated to be 10 Tesla and 57 Å, respectively, for the rapidly quenched YPd2B2C superconducting ribbons.

Time of flight (TOF) spectroscopic measurements are used to diagnose the laser-generated plume of ceramic NdBa2Cu3Ox targets. We have been able to directly correlate the laser-deposited films' properties such as superconductivity, crystallinity, and orientation with plasma properties. Study of the TOF spectra shows that at laser fluences greater than 3 J/cm2 the plume become Nd-rich, and this leads to a low Tc in the deposited film. We have also shown the effect of target density on the energy of the plume species, and through energy considerations we have explained the observed change in the crystalline orientation of films from c- to a-orientation with increasing the target density. Finally, we have examined the oxidation mechanism of NdBa2Cu3Ox thin films, and have shown that highly energetic atomic oxygens have a prevailing role in oxidizing our laser-deposited thin films.

A two-powder process is described for the production of uniform, fine-grained Bi2Sr2Ca2Cu3Oy (Bi-2223) powders. One powder is the Bi2.1−xPbxSr1.9−yCayOz (2:2 Cu-free) phase. The other is a multi-phase powder of approximate overall composition SrCaCu3Oy. The 2:2 Cu-free is one of the first Bi-containing phases to form from a nominal Bi-2223 mixture of oxides and carbonates. This precursor route was chosen for investigation because (1) the powders have very similar particle morphologies and (2) the mixing volumes are closely matched. Both of these characteristics facilitate the milling and blending process. This precursor mix was found to be stable in that explosive grain growth of undesirable phases was not observed during sintering. Critical current densities up to 26,900 A/cm2 in self field at 75 K were obtained in tapes.

The formation of Pb-doped 80 K phase from nitrate precursors was studied in the Bi1.84Pb0.34Sr1.91Ca2.00Cu3.04O10.05 system. Sr(Pb, Bi)O3, Ca5Bi14O26, CuO, and CaO were found to be the intermediate compounds reacting to produce 80 K phase between 600 and 820 °C. Synthesis was complete at 800 °C for 24 h. 110 K phase formed at the expense of 80 K phase at temperatures above 820 °C. Partial melting was detected and 80 K and 110 K phases were unstable in the presence of liquid phase. They decomposed to 2201, Cu2O, and (Ca, Sr, Cu) complex oxides. The melting and decomposition were accompanied by oxygen loss.

Air oxidation of undoped and B-doped polycrystalline diamond films was investigated at temperatures between 500 and 700 °C. Diamond (111) facets were etched for both undoped and B-doped films after 1 h at 700 °C. The etching rate of (111) facet due to oxidation was approximately 50% lower by B-doping of 1 × 1019 cm−3, presumably because of the decrease of sp2 bands and lattice defects that were identified by Raman and photoluminescence spectroscopy. X-ray photoelectron and electron energy loss spectroscopy revealed that by the high temperature treatment, the diamond surface was initially converted into graphite and successively etched by oxygen.

A set of 45° [001] bi-epitaxial YB2Cu3O7−x thin film grain boundaries was studied to compare the effects of the microstructure on transport properties. The grain boundaries were made using two different deposition techniques: pulsed laser deposition (PLD) and pulsed organometallic beam epitaxy (POMBE). The transport properties were highly dependent on the specific growth conditions used, resulting in both fully resistive and superconducting grain boundaries. Subsequent microstructural analysis of the measured boundaries showed that both types (superconducting and resistive) meandered on the length scale of hundreds of nanometers. The major structural difference between the boundaries was at the atomic scale where the resistive boundary had a 1 nm wide disordered region. The direct correlation of microstructure to transport properties demonstrates the importance of the atomic scale structure in the resulting transport behavior.

Well-crystallized polycrystalline thin films of cubic barium titanate (BaTiO3) have been synthesized on Ti-covered Si substrates by exposing the substrates to a Ba(OH)2 aqueous solution at 160 °C and a low pressure less than 1 MPa. It was presumed that the film formation of BaTiO3 involved a dissolution-crystallization mechanism, which provides an attractive approach to produce other titanate films and powders. Also, we have used for the first time this hydrothermal technique to deposit epitaxial (001)-textured PbTiO3 thin films on SrTiO3(100) substrates.

It is shown that additions of Al2O3 (1.0 wt. %) can significantly aid in the isothermal melt processing of Bi2Sr2CaCu2Oy (Bi-2212). Al2O3 additions provide a means for grain refinement of phases present in the partial melt. By limiting grain growth in the partial melt, solidification to form Bi-2212 proceeds more efficiently, resulting in fewer secondary phases and improved transport properties. Aluminum does not substitute into the superconducting phase to any appreciable extent and is present in fully processed material as small, secondary grains of approximate composition Sr2−xCaxAlOy or Bi2Sr4−xCaxAl3Oy · Al2O3 additions were applied to the isothermal melt processing of Bi-2212 thick films and current leads.