Microtexture of highly crystallized graphite as studied by galvanomagnetic properties and electron channeling contrast effect

1996 ◽  
Vol 11 (3) ◽  
pp. 769-778 ◽  
Author(s):  
Yutaka Kaburagi ◽  
Akira Yoshida ◽  
Yoshihiro Hishiyama
Keyword(s):  
Pyrolytic Graphite ◽  
Mean Free Path ◽  
Residual Resistivity ◽  
X Ray Diffraction ◽  
Polyimide Films ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Electron Channeling ◽  
The Mean ◽  
The Difference

The relationship between microtexture and crystallinity of highly crystallized graphites with the residual resistivity ratio ρ300K/ρ4.2K of 3.45–5.50 was investigated. The graphite crystals studied were kish graphite (KG), highly oriented pyrolytic graphite (HOPG), and highly crystallized graphite films prepared from carbonized aromatic polyimide films. The study was made by the observations of an electron channeling pattern and electron channeling contrast image (ECI) under scanning electron microscope and the measurements of x-ray diffraction, magnetoresistance, and Hall coefficient. The values of the mean free path of the carriers λ, which approximates the mean crystal grain size, were estimated to be 2.6–6.1 μm from the magnetoresistance at 4.2 K for the highly crystallized graphites. The values of the average crystal grain diameter D in the basal plane evaluated from ECI were several hundred microns or more for KG, 60 μm for HOPG, and 6 and 12 μm for the graphite films. The difference between the values of λ and D for each crystallized graphite was discussed in relation to other results obtained.

Electron channeling effect on highly oriented graphites–Size evaluation and oriented mapping of crystals

1992 ◽  
Vol 7 (6) ◽  
pp. 1400-1405 ◽  
Author(s):  
Akira Yoshida ◽  
Yoshihiro Hishiyama
Keyword(s):  
Room Temperature ◽  
Crystal Size ◽  
Pyrolytic Graphite ◽  
Residual Resistivity ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Axis Orientation ◽  
Electron Channeling ◽  
Channeling Effect ◽  
Size Evaluation

Structural studies on kish graphite (KG) and highly oriented pyrolytic graphite (HOPG) were performed using the techniques of electron channeling pattern (ECP) and electron channeling micrograph (ECM) in the scanning electron microscope. In the KG specimens the ECP for the single crystal was observed for each specimen, while in the HOPG specimens those of polycrystalline graphites with parallel c-axes were observed. The crystal sizes along the a-axis in the HOPG specimens were evaluated by ECM's. The average crystal size was related to a parameter sensitive to their crystallinity, i.e., the ratio of the resistivity at room temperature to that at 4.2 K (residual resistivity ratio). A mapping of the a-axis orientation of HOPG specimens was carried out.

Cu Ti Formation in Nb Ti/Cu Superconducting Strand Monitored by In Situ Techniques

2010 ◽  
Vol 297-301 ◽  
pp. 695-701
Author(s):  
Ian Pong ◽  
Christian Scheuerlein ◽  
Carmine Senatore ◽  
Ludovic Thilly ◽  
Marco Di Michiel ◽  
...  
Keyword(s):  
Deformation Behaviour ◽  
Mechanical Tests ◽  
Residual Resistivity ◽  
X Ray Diffraction ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Exposure Effect ◽  
In Situ Xrd ◽  
Temperature Exposure

In order to investigate the high temperature exposure effect on Nb Ti/Cu superconducting strands, as might be encountered in joining by soldering and in cabling annealing, X-ray diffraction and resistometry measurements were performed in situ during heat treatment, and complemented by conventional metallography, mechanical tests and superconducting properties measurements. Changes of the Nb Ti nanostructure at temperatures above 300°C are manifested in the degradation of critical current in an applied external magnetic field, although degradation at self field was insignificant up to 400°C for several minutes. Above 500°C, the formation of various Cu Ti intermetallic compounds, due to Ti diffusion from Nb Ti into Cu, is detected by in situ XRD albeit not resolvable by SEM-EDS. There is a ductile to brittle transition near 600°C, and liquid formation is observed below 900°C. The formation of Cu Ti causes a delayed reduction of the residual resistivity ratio (RRR) and adversely affects the deformation behaviour of the strands.

Thermal Expansion, Magnetic and Electrical Properties of Ternary Compound DyCo0.67Ga1.33

2016 ◽  
Vol 848 ◽  
pp. 703-708
Author(s):  
Liu Qing Liang ◽  
Ling Min Zeng ◽  
Shu Hui Liu ◽  
De Gui Li ◽  
Ming Qin
Keyword(s):  
Electrical Resistivity ◽  
Thermal Expansion ◽  
Ternary Compound ◽  
Coefficient Of Thermal Expansion ◽  
Residual Resistivity ◽  
X Ray Diffraction ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
X Ray ◽  
Temperature Range

The ternary compound DyCo0.67Ga1.33 was synthesized and the thermal expansion of DyCo0.67Ga1.33 was studied in the temperature range of 309–608 K by high temperature powder X-ray diffraction technique. The volumetric coefficient of thermal expansion, , can be represented by . Its magnetic properties were measured between 30 and 300 K, and the magnetic susceptibility of DyCo0.67Ga1.33 was found to follow the Curie–Weiss law in the temperature range of 40–300 K. The effective magnetic moment and paramagnetic Curie temperature were estimated to be 9.86 μB and 40.4 K, respectively. Electrical resistivity of the compound DyCo0.67Ga1.33 was also measured between 5 and 300 K. Temperature variation of the electrical resistivity suggests the metallic character of the compound DyCo0.67Ga1.33 with an anomaly detected at 45 K. The residual resistivity ratio RRR of the compound is about 1.2.

Sputtering pressure dependence of hydrogen-sensing effect of palladium films

2009 ◽  
Vol 24 (6) ◽  
pp. 1919-1927 ◽  
Author(s):  
Chung Wo Ong ◽  
Yu Ming Tang
Keyword(s):  
Electrical Resistivity ◽  
Magnetron Sputtering ◽  
Mean Free Path ◽  
Induced Response ◽  
Resistivity Ratio ◽  
Hydrogen Sensing ◽  
The Mean ◽  
Sputtering Pressure ◽  
Specific Volumes ◽  
Hydride Phases

The electrical resistivity ρ of palladium (Pd) films prepared by using magnetron sputtering at different pressures φ ranging from 2 to 15 mTorr showed very different hydrogen (H)-induced response. This reaction is because the mean free path of the particles in vacuum changes substantially with φ, such that the structure of the deposits is altered accordingly. A film prepared at a moderate φ value of 6 mTorr has a moderate strength. After a few hydrogenation-dehydrogenation cycles, some cracks are generated because of the great difference in the specific volumes of the metal and hydride phases. Breathing of the cracks in subsequent switching cycles occurred, which led to the response gain of ρ, defined as the resistivity ratio of the dehydrogenated-to-hydrogenated states during a cycle, to increase to 17. This result demonstrates the attractiveness of using the Pd films in H2 detection application. The H-induced resistive response of the films prepared at other φ values was found to be much smaller.

scholarly journals Proximity effect in [Nb(1.5 nm)/Fe(x)]10/Nb(50 nm) superconductor/ferromagnet heterostructures

2020 ◽  
Vol 11 ◽  
pp. 1254-1263
Author(s):  
Yury Khaydukov ◽  
Sabine Pütter ◽  
Laura Guasco ◽  
Roman Morari ◽  
Gideok Kim ◽  
...  
Keyword(s):  
Intermediate State ◽  
Proximity Effect ◽  
Intermediate Phase ◽  
Ferromagnetic Layer ◽  
Residual Resistivity ◽  
Neutron Reflectometry ◽  
Superconducting Transition ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Weak Ferromagnetic

We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe(x)]10 superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al2O3(1−102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15–20. By using neutron reflectometry we show that Fe/Nb superlattices with x < 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to x = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure.

Origin of Diversified Transport Properties of MgB2

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3672-3674
Author(s):  
Kijoon H. P. Kim ◽  
C. U. Jung ◽  
Heon-Jung Kim ◽  
Min-Seok Park ◽  
Mun-Seog Kim ◽  
...  
Keyword(s):  
Low Temperature ◽  
Transport Properties ◽  
Temperature Region ◽  
Residual Resistivity ◽  
Transition Width ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Excess Mg

We investigated the transport properties of MgB 2 while changing the contents of excess Mg. The samples containing almost no excess Mg showed the highest Tc and the sharpest transition width (ΔTc). A residual resistivity ratio (RRR) of ~ 5.8, and a magnetoresistance (MR) of 12%, at 40 K, were obtained for this stoichiometric sample. Moreover, no upturn of resistivity in a low temperature region at 10 Tesla was observed. However, the samples containing appreciable amounts of excess Mg showed quite different behaviors; the values of ΔTc, RRR and MR were much larger. Surprisingly, big upturn appeared in this Mg-excess MgB 2

scholarly journals High-sensitivity of initial SrO growth on the residual resistivity in epitaxial thin films of SrRuO$$_3$$ on SrTiO$$_3$$ (001)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Uddipta Kar ◽  
Akhilesh Kr. Singh ◽  
Song Yang ◽  
Chun-Yen Lin ◽  
Bipul Das ◽  
...  
Keyword(s):  
Volume Fraction ◽  
High Sensitivity ◽  
Orthorhombic Phase ◽  
Residual Resistivity ◽  
Epitaxial Thin Films ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Growth Technique ◽  
X Ray ◽  
High Crystallinity

AbstractThe growth of SrRuO$$_3$$ 3 (SRO) thin film with high-crystallinity and low residual resistivity (RR) is essential to explore its intrinsic properties. Here, utilizing the adsorption-controlled growth technique, the growth condition of initial SrO layer on TiO$$_2$$ 2 -terminated SrTiO$$_3$$ 3 (STO) (001) substrate was found to be crucial for achieving a low RR in the resulting SRO film grown afterward. The optimized initial SrO layer shows a c(2 $$\times $$ × 2) superstructure that was characterized by electron diffraction, and a series of SRO films with different thicknesses (ts) were then grown. The resulting SRO films exhibit excellent crystallinity with orthorhombic-phase down to $$t \approx $$ t ≈ 4.3 nm, which was confirmed by high resolution X-ray measurements. From X-ray azimuthal scan across SRO orthorhombic (02 ± 1) reflections, we uncover four structural domains with a dominant domain of orthorhombic SRO [001] along cubic STO [010] direction. The dominant domain population depends on t, STO miscut angle ($$\alpha $$ α ), and miscut direction ($$\beta $$ β ), giving a volume fraction of about 92 $$\%$$ % for $$t \approx $$ t ≈ 26.6 nm and $$(\alpha , \beta ) \approx $$ ( α , β ) ≈ (0.14$$^{\mathrm{o}}$$ o , 5$$^{\mathrm{o}}$$ o ). On the other hand, metallic and ferromagnetic properties were well preserved down to t$$\approx $$ ≈ 1.2 nm. Residual resistivity ratio (RRR = $$\rho ({\mathrm{300 K}})$$ ρ ( 300 K ) /$$\rho ({\mathrm{5K}})$$ ρ ( 5 K ) ) reduces from 77.1 for t$$\approx $$ ≈ 28.5 nm to 2.5 for t$$\approx $$ ≈ 1.2 nm, while $$\rho ({\mathrm{5K}})$$ ρ ( 5 K ) increases from 2.5 $$\upmu \Omega $$ μ Ω cm for t$$\approx $$ ≈ 28.5 nm to 131.0 $$\upmu \Omega $$ μ Ω cm for t$$\approx $$ ≈ 1.2 nm. The ferromagnetic onset temperature ($$T'_{\mathrm{c}}$$ T c ′ ) of around 151 K remains nearly unchanged down to t$$\approx $$ ≈ 9.0 nm and decreases to 90 K for t$$\approx $$ ≈ 1.2 nm. Our finding thus provides a practical guideline to achieve high crystallinity and low RR in ultra-thin SRO films by simply adjusting the growth of initial SrO layer.

Mechanical, Thermal and Electrical Characteristics of Conventionally Cast and Cold-Rolled 5754-Sc-Zr Aluminium Alloy

2019 ◽  
Vol 22 ◽  
pp. 55-64
Author(s):  
Martin Vlach ◽  
Veronika Kodetová ◽  
Hana Kudrnová ◽  
Michal Leibner ◽  
Marián Vlček ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Electron Backscatter Diffraction ◽  
Residual Resistivity ◽  
Precipitation Process ◽  
Residual Resistivity Ratio ◽  
Scanning Calorimetry ◽  
Resistivity Ratio ◽  
Cold Rolled ◽  
Initial Difference ◽  
C 30

The effect of cold-rolling on mechanical, thermal, and electrical properties as well as microstructure behaviour of the Al-2.93wt.%Mg-0.34wt.%Mn-0.33wt.%Si-0.22wt.%Fe-0.19wt.%Cr-0.24wt.%Sc-0.06wt.%Zr was studied. The material was investigated during step-by-step isochronal annealing in a temperature range from room temperature up to 540 °C and during isothermal annealing at 200, 450 and 550 °C. Precipitation reactions were studied by electrical resistometry, conductivity, (micro) hardness measurements and differential scanning calorimetry. The hardening effect appears due to the additional precipitation of the Al3Sc and/or Al3(Sc,Zr) particles. The distinct changes in residual resistivity ratio above ~ 330 °C are probably caused by precipitation of the Mn (,Fe,Cr)-containing particles. This precipitation process is highly influenced by cold rolling but it has a negligible effect on hardness. The apparent activation energy values for additional formation of the Al3Sc and/or Al3(Sc,Zr) particles were determined. The kinetics of the Al3(Sc,Zr)-phase precipitation seems to be independent of Mn-and Mg-addition in the studied alloys. A partial recrystallization of the cold-rolled alloy was registered by electron backscatter diffraction after annealing at 550 °C. The initial difference in microhardness introduced by cold rolling is almost removed after annealing at 550 °C/30 min.

scholarly journals Variation of transition temperatures and residual resistivity ratio in vapor-grown FeSe

2016 ◽  
Vol 94 (2) ◽  
Author(s):  
A. E. Böhmer ◽  
V. Taufour ◽  
W. E. Straszheim ◽  
T. Wolf ◽  
P. C. Canfield
Keyword(s):  
Residual Resistivity ◽  
Transition Temperatures ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio

HIGH QUALITY FULLY IN-SITU MgB2 THIN FILMS OBTAINED BY DC MAGNETRON SPUTTERING

2003 ◽  
Vol 17 (04n06) ◽  
pp. 779-784 ◽  
Author(s):  
M. G. MAGLIONE ◽  
F. CHIARELLA ◽  
R. DI CAPUA ◽  
R. VAGLIO ◽  
M. SALVATO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Magnetron Sputtering ◽  
Target Surface ◽  
Residual Resistivity ◽  
Precursor Film ◽  
Large Area ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio

MgB 2 thin films were grown in-situ at INFM- University of Naples by a magnetron sputtering technique in a UHV system (10-7 Pa) equipped with 3 focused 2′′ magnetron sources (a stoichiometric MgB 2 and metallic Mg and B targets by Superconducting Components Inc.). The substrates (sapphire or MgO) were placed "on axis" at 7 cm from the target surface on the surface of a molybdenum heater that could be operated up to 1000°C under vacuum. Best results were obtained codepositing MgB 2 and Mg at equal sputtering power (500W) for 10 min on cold substrates, resulting in a Mg rich Mg-B precursor film. The films were then annealed inhyphen;situ at 830°C for 10 min in a In sealed Nb box in presence of saturated Mg vapor. The process is highly reproducible and can be easily scaled to produce large area films. The resulting films were about 1μm thick, with 100nm surface roughness as measured by AFM Resistive transition showed a maximum T c of 35 K and a transition width lower than 0.5 K. The residual resistivity ratio was 1.6 for the best sample. Resistivity measurements in external magnetic field up to 8 T have been performed both in parallel and perpendicular configuration. The upper critical magnetic field vs. temperature behavior has been determined from the experimental data and the superconducting anisotropy has been calculated for samples with different T c .

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