X-ray Pole Figure Research Articles

Structural and electrical characterization of magnetoresistive La0.7Ca0.3MnO3 thin films

We have investigated the structural and electrical properties of La0.7Ca0.3MnO3 thin films grown both by pulsed laser or DC-sputtering deposition techniques on SrTiO3 (100) substrates. X-ray diffractograms and pole figures revealed the epitaxial character of the samples. Resistance vs. temperature measurements without applied magnetic field showed the metal–insulator transition temperature (TMI) in the range of 220–260K. The magnetoresistance temperature dependence was also investigated and correlated with the thickness of the films, the oxygen annealing treatment and the presence of lattice defects.

Deposition of CeO 2 and NiO buffer layers for YBCO coated conductors on biaxially textured Ni substrates by a MOCVD technique

CeO 2 and NiO buffers for YBCO coated conductors were deposited on biaxially textured Ni substrates by a metal-organic chemical vapor deposition method. The degree of texture and surface roughness of the oxide films were analyzed by X-ray pole figure, atomic force microscope (AFM) and scanning electron microscopy. The texture of deposited CeO 2 films was a function of deposition temperature and oxygen partial pressure ( P O 2 ). The (2 0 0) texture of CeO 2 was fully developed at T=500–520 °C and P O 2 =3.33 Torr. The growth rate of the CeO 2 films was 200 nm/min at T=520 °C and P O 2 =2.30 Torr, which is much faster than those prepared by other physical deposition methods. The (2 0 0) texture of NiO was formed at T=450 °C and P O 2 =1.67 Torr. The full width half maximum of the both films was in the range of 8–10°. The AFM surface roughness of the films was between 3.0–10 nm, depending on the deposition temperature.

Subgrain structures and superconductivity in RE–Ba–Cu–O bulk superconductors

We have studied the microstructures of subgrains in large single-domain RE–Ba–Cu–O (RE=Y, Nd, Sm) bulk superconductors through microscopic observation and microarea X-ray pole figure analyses. The misorientation angle of subgrains increases as the crystal growth proceeds, and thus more crystal defects such as dislocations are seen at the later stage of the growth. Electron backscatter diffraction technique was successfully utilized for characterizing the subgrain boundaries. Electric and magnetic measurements for several samples containing different subgrain geometries have been performed. The results of I– V and resistivity measurements indicated that subgrains act as weak-links especially in a high magnetic field region.

Pulsed laser deposition of c-axis untilted YBCO films on c-axis tilted ISD MgO-buffered metallic substrates

Biaxially textured MgO template layer was deposited on nontextured metal substrates by inclined-substrate deposition (ISD) at a deposition rate of 24–600 nm/min. c-axis untilted YBa 2Cu 3O 7− x (YBCO) films were deposited on these MgO-buffered substrates by pulsed laser deposition. The crystalline structures of the YBCO films and MgO layers were examined by X-ray pole figure analysis, X-ray φ-scans, and χ-scans. A tilt angle of 33° of the MgO[0 0 1] with respect to the substrate normal and c-axis untilted YBCO films were observed, respectively. Good biaxial texture of these films with full-width-at-half-maximum values of 13.8° and 10.6° for the φ-scans of YBCO(1 0 3) and MgO(2 2 0), respectively, were obtained. Morphologies were examined by scanning electron microscopy, which revealed a unique roof-tile feature and columnar grain growth for the ISD MgO layer. Raman spectroscopy and magneto-optical image technique were also used to evaluate the quality of the YBCO film. An angular dependence of J c on the direction of an applied magnetic field confirmed the c-axis untilted orientation of the YBCO films. T c=90 K with sharp transition and J c=3.0×10 5 A/cm 2 at 77 K in zero field were obtained on 0.4-μm-thick YBCO films.

Growth and Characterization of YbBCO Films on Textured Gd2O3 Buffer-Layered Ni Tapes: All Sol–Gel Process

YbBa2Cu3O7−x (YbBCO) thick films were grown on buffered, cube-textured Nickel tapes by sol–gel dip-coating method. Yb-123 films were prepared using solutions of Yb, Ba, and Cu organometallic compounds. A solution-based Gd2O3 buffer layer was deposited by dip-coating process with excellent texture and uniformity. The texture development and surface morphology of the buffer-layer films were examined by X-ray diffraction, pole figures, and ESEM analysis. Microstructure and characterization of Yb-123 films were done by ESEM, EDS, and XRD analysis. Tc and Jc were conducted by four-wire measurement method

Real time in-situ stress evolution investigation of highly textured electrodeposited bismuth thin films

AbstractBismuth, a semi-metal with very long mean free path and large magnetoresistance (MR) effect, is a novel candidate material for thin film spintronic devices. Electrochemical deposition followed by a post-deposition anneal has resulted in highly textured bismuth films as characterized by x-ray diffractometry and pole figure measurements. A highly sensitive, real time in-situ stress measurement system was designed and employed to study stress generation during bismuth film growth. Bismuth films displayed a monotonically increasing compressive stress during deposition. The magnitude of the compressive stress decreased with the deposition rate in the range 1.5 Å/sec to 50 Å/sec.

Pt-10 mass%Rh合金における立方体集合組織の形成

Using the X-ray pole figure method, hardness test and optical metallography, rolling and recrystallization textures were investigated. After 98% cold reduction, copper type rolling texture developed at the rolling surface. Sharp cube texture with orientational spread around rolling direction was observed after annealing. To intensify the cube texture, the process of partial annealing and light rolling before final annealing is effective in the platinum-rhodium alloy as in the case of aluminum. Orientational spread around the rolling direction was attributed to lattice rotation during rolling in the cube band near to the specimen edge.

Nucleation and growth kinetics of preferred C54 TiSi2 orientations: time-resolved x-ray diffraction measurements

The transformation from the C49 to the C54 phase in TiSi2 thin films has been studied for more than a decade because of its importance to the semiconductor industry. In previous work we identified three dominant C54 orientations in TiSi2 thin films on Si(001) substrates using x-ray pole figure analysis. In the current study the evolution of the three prominent C54 texture components was further examined using synchrotron based time-resolved in situ x-ray diffraction. The kinetics results show significant differences in the nucleation and growth kinetics of the individual orientations. Simulations suggest that this could be explained by an inhomogeneous nucleation of different texture components in the thin film, but not by simple differences in nucleation and/or growth rates. Classical Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis of nucleation and growth was applied to model the C49–C54 phase transformation kinetics for each C54 orientation. These results showed a systematic decrease of the Avrami exponent n from 3 to 2 with increasing annealing temperature. Within a JMAK approach this could be explained by the presence of a limited number of C54 nucleation sites coupled with a faster increase in nucleation rate than in growth velocity with increasing anneal temperature.

Texture of TiSi2 thin films on Si (001)

The texture of blanket C49 and C54 phase TiSi2 films on Si (001) substrates was examined with x-ray pole figure analysis. Textures were studied both in films with initial Ti deposited by sputtering and by low-temperature, plasma assisted chemical vapor deposition. Detailed differences were observed between silicide films grown by subsequently annealing films deposited with the two different methods. However, in both cases, the dominant C49 phase orientational relationships develop with respect to the substrate (001) planes. In contrast, we find that the dominant crystallographic relationships of the C54 phases in both cases are not with the surface (001) plane of the substrate, but instead with the Si (111) planes. Texturing in the case of the sputtered films is particularly complex with one prominent orientation having C54 (11¯0)‖(1¯11) Si with C54 (3̄3̄1̄)‖(011̄) Si and a second having C54 (1¯03¯)‖(1̄1̄1) Si with C54 (040)‖(11¯0) Si. These orientations, which suggest local epitaxy of the disilicide with the Si {111} planes, have not been previously identified for C54 TiSi2 growth on Si (001) substrates. This strong orientational relationship suggests that significant {111} faceting of the Si surface may occur during the silicide formation.

Enhanced ionic conductivity and mesoscopic size effects in heterostructures of BaF 2 and CaF 2

Ionic heterolayers of CaF 2/BaF 2/CaF 2 have been prepared by molecular beam epitaxy (MBE). The spacing has been varied from ∼1 nm to ∼1 μm. In the range of 1 μm to 5 nm, the conductivity (measured effective conductivity parallel to the interface) increases progressively with the increased interfacial density. This is even true for spacings in the sub-Debye range. For comparatively large spacings (>50 nm), semi-infinite space charges provide a quantitative description, while the behavior at smaller spacings reveals nano-size anomalies. At spacings smaller than ∼5 nm, the conductivity decreases. The results clearly demonstrate the possibility to prepare artificial ion conductors and the potential of mesoscopic ion conduction. The paper describes transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray pole figure, secondary ion mass spectrometry (SIMS) and impedance spectroscopic characterization.

Inclined-substrate deposition of biaxially textured template for coated conductors

Inclined-substrate deposition (ISD) offers the potential for rapid production of high-quality biaxially textured buffer layers suitable for YBCO-coated conductors. We have grown biaxially textured MgO films by ISD at deposition rates of 20–100 Å/s. Columnar grain structures with roof-tile-shaped surfaces were observed in these films. X-ray pole figure analysis revealed that the (0 0 2) plane of the ISD MgO films is tilted at an angle from the substrate normal. A small φ-scan full-width at half-maximum of ≈9° was observed on MgO films deposited with an inclination angle of 55°. YBCO films were grown on ISD-MgO-buffered Hastelloy substrates by pulsed laser deposition. We obtained a critical current density of ≈2×10 5 A/cm 2 at 77 K in self-field on a sample that is 0.5 μm thick, 0.5 cm wide, and 1 cm long.

Subgrain structures and their effects on critical current properties in large single-domain RE123 bulk superconductors

We have studied the microstructures of subgrains in large single-domain RE123 (RE=Y, Sm) bulk superconductors through microscopic observation and X-ray pole figure analyses. We have found that misorientation of the subgrains increases along with the crystal growth, and also that the misorientation has positive relation to the size and concentration of the second-phase particles. Such subgrains are considered to affect current carrying capabilities in bulk materials, so that we performed magnetic and electric measurements for several samples having different subgrain structures. The relationships between obtained J c– B or AC transport characteristics and subgrain geometries are discussed.

Ion-beam-assisted deposition of biaxially aligned yttria-stabilized zirconia template films on metallic substrates for YBCO-coated conductors

Biaxially textured yttria-stabilized zirconia (YSZ) films were grown on mechanically polished Hastelloy C276 (HC) substrates by ion-beam-assisted deposition and electron-beam evaporation. The surface root-mean-square (RMS) roughness of the polished HC substrates was ≈3 nm, as measured by atomic force microscopy (AFM). A water-cooled sample stage was used to hold the substrate temperature below 100 °C during deposition. RMS roughness of ≈3.3 nm was measured on the deposited YSZ films by AFM. X-ray pole figures were conducted for texture analysis; in-plane texture measured from YSZ (111) ϕ-scan FWHM was 13.2° and out-of-plane texture from the YSZ (002) ω-scan FWHM was 7.7°. An ≈10 nm thick CeO2 buffer layer was deposited on the YSZ film at 800 °C before YBCO films were ablated by pulsed laser deposition at 780 °C in a 250 mTorr flowing oxygen environment. Good in-plane texture with FWHM ≈ 7° was observed in YBCO films. Tc = 90 K, with sharp transition, and transport Jc of ≈2.2 × 106 A cm−2 were observed in a 0.5 μm thick, 5 mm wide, and 1 cm long sample at 77 K in self-field.

Growth and properties of YBCO thin films on polycrystalline Ag substrates by inclined substrate pulsed laser deposition

Fully c-axis-oriented YBCO films were directly deposited on polycrystalline silver substrates by inclined substrate pulsed laser ablation. The orientation and microstructure of the YBCO films were characterized by x-ray diffraction 2θ-scans, Ω-scans and pole figure analysis. Surface morphology was examined by scanning electron microscopy. Irregular-mosaic-shaped supergrains were observed in the films. Raman spectroscopy was used to evaluate the quality of the YBCO films. The superconducting transition temperature (Tc) and the critical current density (Jc) of the films were determined by inductive and transport measurements, respectively. Tc = 91 K with sharp transition and Jc = 2.7 × 105 A cm−2 at 77 K in zero field were obtained on a film that was 0.14 μm thick, 5 mm wide and 10 mm long. This work demonstrated a promising approach to obtain high-Jc YBCO films on nontextured polycrystalline silver substrate.

Temperature effect of dynamic anisotropic elastic constants of Zr–2.5Nb pressure tube by resonant ultrasound spectroscopy

Dynamic anisotropic elastic constants of CANDU Zr–2.5Nb pressure tube materials were determined by high temperature resonant ultrasound spectroscopy (RUS). The resonance frequencies were measured using a couple of alumina waveguides and wide-band ultrasonic transducers in a small furnace. The rectangular parallelepiped specimens were fabricated along with the longitudinal, radial and transverse direction of the pressure tube. The initial estimates for RUS were obtained from the orientation distribution function by X-ray pole figure and elastic stiffness of single crystal zirconium. A nine elastic stiffness tensor for orthotropic symmetry was determined in the range of room temperature ∼500 °C. As the temperature increases, the elastic constant tensor, c ij gradually decreases. Higher elastic constants along the transverse direction compared to those along the longitudinal or radial direction are similar to the case of Young's modulus or shear modulus. A crossing of elastic constants along the longitudinal direction and radial direction was observed near 120–150 °C. This fact could correlate to the crossing characteristics of c 44 and c 66 of a zirconium single crystal in the temperature range.

Epitaxial nucleation and growth of buffer layers and Y123 coated conductors deposited by metal-organic decomposition

Solution-based deposition of buffer and superconductor layers offers routes to a low-cost YBCO coated conductor technology for high temperature superconductor tapes. In this work we explore the possibility of the preparation procedure of BaZrO 3 buffer and YBCO layers on SrTiO 3 (STO) single crystal substrates by metal-organic decomposition. BaZrO 3 buffer layers have been processed on single crystal substrates using a precursor solution based on barium acetate and zirconium 2,4-pentadionate in acetic acid. YBCO superconducting films were prepared on STO single crystals using trifluoroacetate precursors. X-ray diffraction and pole figure analyses denote good phase purity and high in-plane alignment (<1.5°). SEM and AFM microstructural studies evidence a low degree of roughness and porosity of the layer. These techniques together with μ-Raman spectroscopy, transverse SEM observations, and studies by SQUID magnetometry exhibit the existent relation between the different microstructural characteristics and their superconducting properties.

Subgrains in large-grain RE123 bulk superconductors

We have investigated the microstructures of large-grain RE123 (RE = Y, Sm) bulk superconductors with an emphasis placed on the effects of subgrains on superconducting properties. For the samples grown by slow-cooling, the misorientation angles of the subgrains were larger at the later stage of the growth. For isothermally grown samples, subgrains are likely to form under large undercooling. Based on the results of micro-area x-ray pole figure analyses, the possible mechanism of subgrain formation was concluded to be the accumulation of dislocations formed as a result of entrapment of RE211 inclusions during crystal growth. Both magnetization and transport measurements showed that the subgrains act as weak-links. Hence the amount of subgrains should be minimized for the fabrication of high performance large-grain RE123 materials.

Development of YBCO-coated conductors for electric power applications

Biaxially textured MgO template films have been fabricated on a Ni-based alloy substrate (Hastelloy C276) by inclined-substrate deposition (ISD), using electron beam evaporation, at the high deposition rate of 120–300 nm/min. Buffer films were subsequently deposited on these template films, and YBCO films were finally deposited by pulsed laser deposition (PLD). Crystal textures of the YBCO films were examined by X-ray pole figure, φ- and ω-scans analysis. Good in-plane and out-of-plane textures were observed, with MgO(0 0 2) φ-scan full-width-at-half-maximum (FWHM) of 10.0° and ω-scan FWHM of 5.5°, for a film deposited with an incline angle of 55°. YBCO films were epitaxially grown on ISD MgO-buffered Hastelloy C276 substrates by PLD. T c of 90 K with sharp transition and transport J c of ≈1.4×10 5 A/cm 2 were obtained on a 0.5-μm-thick YBCO film at 77 K in zero field.

Inclined-substrate deposition of biaxially aligned template films for YBCO-coated conductors

Inclined-substrate deposition (ISD) of magnesium oxide (MgO) produces biaxially textured template films at high deposition rates. This process is promising for the fabrication of the second-generation superconducting wires. Biaxially aligned MgO films (≈1.5 μm thick) were deposited on polished Hastelloy C276 (HC) substrates by ISD at deposition rates of 20–100 Å/s. Buffer films were subsequently deposited on these template films, and YBCO films were deposited epitaxially on the substrates by pulsed laser deposition. X-ray pole figure analysis and φ- and ω-scans were used for texture characterization. Good in- and out-of-plane textures were observed, with MgO(0 0 2) φ-scan full-width at half maximum (FWHM) of 9.2° and ω-scan FWHM of 5.4°, respectively. T c of 90 K with a sharp transition, and J c≈2×10 5 A/cm 2, were obtained on a 0.5 μm thick, 0.5 cm wide, and 1 cm long YBa 2Cu 3O 7− δ (YBCO) film at 77 K in self-field.

Effects of Ti on the formability of Ti−IF steels

In the present study, the influence of precipitations and texture evolution on the sheet forming properties of Ti added IF (Interstitial Free) steels has been investigated. Precipitations in Ti−IF steels were examined using TEM. Equilibrium precipitation behavior was simulated to predict the proper amount of Ti addition to IF steels to fix interstitial atoms. Texture evolution was studied by employing X-ray pole figure measurement and ODF analysis. The formability of Ti−IF steels was improved by fixing interstitial atoms C, N, S with Ti. Additional improvement of formability was also found due to the existence of solute Ti of about 0.02 wt.%. A systematic analytical methodology for the precipitation behavior and texture evolution of Ti−IF steels was established for the development of IF steels.