Browsing by Author "Ozturk O."

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A comprehensive study on mechanical properties of Bi1.8Pb 0.4Sr2MnxCa2.2Cu3.0O y superconductors
(2013-08-01) Dogruer M.; Karaboga F.; Yildirim G.; Terzioglu C.; Ozturk O.
This study manifests the crucial change in the mechanical performances of Bi1.8Pb0.4Sr2MnxCa 2.2Cu3.0Oy superconductor samples (x = 0, 0.03, 0.06, 0.15, 0.3 and 0.6) prepared by conventional solid-state reaction method by use of Vickers microhardness (Hv) measurements carried out at different applied loads, (0.245 N ≤ F ≤ 2.940 N). Load dependent microhardness, load independent microhardness, Young's (elastic) modulus and yield strength values being account for the potential technological and industrial applications are evaluated from the hardness curves and compared with each other. It is found that the Hv, elastic modulus and yield strength obtained decrease (increase) with the enhancement of the applied load for the undoped (doped) samples. Surprisingly, the results of the Hv values illustrate that the samples doped with x = 0.03, 0.06, 0.15, 0.3 and 0.6 exhibit reverse indentation size effect (RISE) feature whereas the pure sample obeys indentation size effect (ISE) behavior. Furthermore, the experimental results are examined with the aid of the available methods such as Meyer's law, proportional sample resistance model (PSR), elastic/plastic deformation (EPD), Hays-Kendall (HK) approach and indentation-induced cracking (IIC) model. The results inferred show that the hardness values calculated by PSR and EPD models are far from the values of the plateau region, meaning that these models are not adequate approaches to determine the real microhardness value of the Mn doped Bi-2223 materials. On the other hand, the HK approach is completely successful for the explanation of the ISE nature for the pure sample while the IIC model is obtained to be the best model to describe the hardness values of the doped materials exhibiting the RISE behavior. Additionally, the bulk porosity analysis for the samples reveals that the porosity increases monotonously with the increment in the Mn inclusions inserted in the Bi-2223 system, presenting the degradation of the grain connectivity. © 2013 Springer Science+Business Media New York.
A detailed research for determination of Er/Gd co-doping effect in ZnO-NPs thin films on optical, electrical and crystallographic properties
(2023-01-01) Asikuzun Tokeser E.; Ozturk O.; Kurnaz S.; Cicek C.; Seydioglu T.
Undoped, Er and Gd doped ZnO transparent semiconductor thin films were coated on non-alkaline glass using the sol–gel dip-coating method. Methanol and ethanolamine (MEA) were chosen as solvents and stabilizers. Er doping concentration was maintained at 5%. The effects of both different dopants and different dip numbers on the optical, electrical and structural properties of ZnO thin films were analyzed. According to the XRD patterns, hexagonal structure was seen in all films. The optical transmittance of impurity elements doped ZnO thin films increased with the increasing of Gd doping. High transparency was determined to doped films in the visible region. The electrical properties of the Er/Gd co-doped ZnO thin films were measured by Van der Pauw Hall measurements technique that determined the bulk carrier concentration, the Hall mobility and the resistivity at room temperature. Er and Gd doped films shown lower Hall mobility and resistivity than undoped ZnO thin films. In the bulk carrier concentration, it was seen that there was an increase in 5 dip and 10 dip, while it decreased in 20 dip.
A study on magnetoresistivity, activation energy, irreversibility and upper critical field of slightly Mn added Bi-2223 superconductor ceramics
(2012-05-01) Dogruer M.; Zalaoglu Y.; Varilci A.; Terzioglu C.; Yildirim G.; Ozturk O.
This study discusses the effect of Mn addition on the superconducting and physical properties in Bi 1.8Pb 0.4Sr 2Mn xCa 2.2Cu 3.0O y bulk superconductors with x = 0, 0.03,0.06,0.15, 0.3, and 0.6 by means of themagne-toresistivity measurements. The magnetoresistivity of the samples prepared using the standard solid-state reaction method was measured for different values of the applied magnetic field strengths. The superconducting and physical properties of the samples such as the zero resistivity transition temperatures (T c), irreversibility fields (μ 0Hi rr), and upper critical fields (μ 0H c2) were deduced from the magnetoresistivity curves. Moreover, thermally activated flux creep model was studied for activation energy (U0) values of the samples. According to the results of the measurements, not only were the T c and U0 values of the samples found to decrease significantly but the μ 0Hi rr and μ 0H c2 values were also observed to reduce with the increase in the Mn addition, indicating that the doping degrades the physical and superconducting properties of the samples. © 2012 Springer Science+Business Media, LLC.
A study on nucleation, crystallization kinetics, microstructure and mechanical properties of Ru-Bi partial substituted BSCCO glass ceramics
(2016-02-01) Ozturk O.; Gokcen T.; Cavdar S.; Koralay H.; Tasci A.T.
This study deals with the effects of Ru-Bi partial substitutions on the thermal, structural and mechanical properties of Bi1.8-x Ru x Pb0.2Sr2CaCu2O10+δ (x = 0.0, 0.025, 0.050, 0.075) system, produced by using glass ceramics method. The effects of Ru-Bi partial substitutions on glass transition, nucleation and crystallization temperature were analyzed via differential thermal analyzer (DTA). Besides, microstructure and micromechanical properties of Ru-Bi partially substituted BSCCO glass ceramics were also investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers microhardness measurements. From the DTA results, nucleation kinetics were studied by using Ozawa, Augis-Bennett, Takhor and Kissinger equations. In addition to this, activation energies and Avrami parameters were also calculated. According to the results of the thermogravimetric analyses, the amount of oxidation was seen to be increased with increasing Ru concentration. Moreover, the lattice parameters, volume fractions and surface morphologies of our newly produced glass ceramics were investigated by XRD and SEM measurements, respectively. RISE behavior obtained from the microhardness measurements for all samples. Microhardness, elastic modulus, yield strength and fracture toughness values decreased with increasing Ru doping.
Ac Susceptibility Measurements and Mechanical Performance of Bulk MgB2
(2015-07-24) Ozturk O.; Asikuzun E.; Kaya S.; Erdem M.; Safran S.; Kilic A.; Terzioglu C.
The effects of Ar ambient pressure (vacuum and 0, 10, and 20 B) and annealing times (0.5 and 1 h) on microstructural, superconducting, and mechanical properties of bulk superconducting MgB2 are investigated. The samples are produced using the solid-state reaction method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements are performed for determination of the crystal structure and surface morphology of MgB2 samples, respectively. The superconducting properties are studied by AC magnetic susceptibility measurements. Microhardness analyses are made using the Vickers microhardness test for determination of mechanical properties of all samples. Increasing the Ar pressure decreases the lattice parameters and hence the average grain size. Increasing the annealing time results in larger lattice parameters and larger grain formation. The susceptibility measurements revealed a two-step transition which is reminiscent of granular superconductors. The intra-grain transition temperature is determined to be 38.4 K for all samples. The inter-grain transition temperature of 37.2 K is obtained for samples produced under Ar ambient pressure. The samples produced under Ar ambient pressure have better superconducting properties than the ones produced in vacuum. Increasing the annealing time under vacuum further decreases the superconducting properties probably due to Mg loss.
Analysis of indentation size effect (ISE) behavior in low-load Vickers microhardness testing of (Sm123) 1-x (Nd123) x superconductor system
(2013-01-01) Celik S.; Ozturk O.; Coşkun E.; Sarıhan M.; Asikuzun E.; Ozturk K.; Terzioglu C.
Indentation size effect (ISE) for (Sm123) 1-x (Nd123) x superconducting samples which were fabricated by the solid state reaction technique for values of x = 0.00, 0.05, 0.10, 0.20, and 0.30 was investigated by analyzing the theoretical models. When the experimental data of a number of single crystals which have the different crystal structure and different chemical bonding inside the polycrystallined samples were analyzed with the ISE models, the sample encountering with resistance and elastic deformation was observed as well as plastic deformation. The microhardness values on different surfaces of materials were calculated by using Meyer Law, proportional specimen resistance model, modified proportional specimen resistance model, elastic/plastic deformation model and the Hays-Kendall (HK) approach. The results showed that the HK approach was determined as the most successful model. Furthermore, X-ray powder diffraction and scanning electron microscope measurements were analyzed for superconducting properties of (Sm123) 1-x (Nd123) x superconductor system. The results showed that microhardness values at the minimum load and averaged plateau region of load increased with increase of Nd123 concentration. Nd123 content can be used as to be estimated the microhardness value of (Sm123) 1-x (Nd123) x superconducting sample in the range of 0.878-2.717 GPa. The control of the microhardness value by using Nd123 content in (Sm123) 1-x (Nd123) x superconducting structure can be useful in technological applications in superconductivity industry. © 2013 Springer Science+Business Media New York.
Analysis of indentation size effect on mechanical properties of Cu-diffused bulk MgB2 superconductor using experimental and different theoretical models
(2013-01-01) Dogruer M.; Yildirim G.; Ozturk O.; Terzioglu C.
This study indicates the change of the electrical, microstructural, physical, mechanical and superconducting properties of Cu-diffused bulk MgB 2 superconductors by means of scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), microhardness and dc resistivity measurements. The samples are prepared at different annealing temperatures in the range from 650 to 850 â̂̃C. Electrical and superconducting properties of samples are estimated from the dc electrical resistivity measurements. Moreover, microhardness measurements are performed to investigate the mechanical properties. Further, phase composition, grain sizes and lattice parameters are determined from the XRD measurements. At the same time, the surface morphology and grain connectivity of the samples are examined by SEM investigations. The measurements conducted demonstrate that both the Cu diffusion into the MgB2 system and the increment in the diffusion-annealing temperature increase the critical transition temperatures. Similarly, microstructure and grain size improve while the voids and porosity decrease with the increase of the diffusion-annealing temperature. In addition, the experimental results of the microhardness measurements are investigated using the Meyer's law, PSR (proportional specimen resistance), modified PRS (MPSR), elastic-plastic deformation model (EPD) and Hays-Kendall (HK) approach. The obtained microhardness values of the samples decrease with the increase of the diffusion-annealing temperature up to 850 â̂̃C. The Hays-Kendall approach is found to be the most successful model describing the mechanical properties of the samples studied in this work. © 2012 Springer Science+Business Media, LLC.
Breaking point of the harmony between Gd diffused Bi-2223 slabs with diffusion annealing temperature
(2013-01-01) Aydın H.; Babanli A.; Altintas S.; Asikuzun E.; Soylu N.; Ozturk O.; Dogruer M.; Terzioglu C.; Yildirim G.
This comprehensive study reports the role of annealing temperature on the microstructural, superconducting and mechanical characteristics of the Gd diffused Bi-2223 superconducting ceramics produced by the conventional solid-state reaction route at 840 C for the annealing duration of 48 h. For the material characterization, the standard experimental methods such as dc resistivity (ρ-T), transport critical current density, X-ray powder diffraction, scanning electron microscopy and Vickers microhardness measurements are performed systematically. All the results obtained show that all the measured characteristic properties, being in charge of the applications in the industry, engineering and technology, improve until a certain diffusion annealing temperature of 800 C beyond which they tend to degrade considerably. The increase in the properties is mostly related to the transition from the inherent overdoped state of the pure Bi-2223 material to optimum doped state with the diffusion annealing temperature, confirming the penetration of the sufficient Gd nanoparticles into the crystal structure. On the other hand, the suppression in the superconducting properties stems from the appearance of the porosity, defects, disorder and localization problem in the polycrystalline Bi-2223 superconducting matrix. This is attributed to the decrement of the average crystallite size and mobile hole concentration in the Cu-O 2 layers and especially the retrogression of the crystallinity in the system. As for the mechanical characteristics, Vickers microhardness measurements exerted in the applied indentation test load range of 0.245-2.940 N indicate that the Gd diffused bulk superconducting samples exhibit the typical indentation size effect behavior. With the enhancement in the annealing temperature up to 800 C, the significant increase in the elastic modulus, yield strength and fracture toughness is one of the most striking points in the paper. The long and short of it is that the excess diffusion annealing temperature damages the fundamental characteristics of the Bi-2223 system. © 2013 Springer Science+Business Media New York.
Change of formation velocity of Bi-2212 superconducting phase with annealing ambient
(2013-11-01) Ozturk O.; Yildirim G.; Asikuzun E.; Coskunyurek M.; Yilmazlar M.; Kilic A.
This exhaustive study enables the researchers to recognize the role of the annealing conditions (temperature and time) on the microstructural, mechanical, electrical and superconducting properties of the Bi-2212 superconducting material with the aid of ρ-T, X-ray diffraction, scanning electron microscopy and Vickers microhardness (Hv) measurements. For this aim, the superconducting samples are elaborated by standard solid-state reaction route at different annealing temperature and different annealing duration. The results show that the annealing temperature of 840 C and the annealing duration of 72 h are the best for the formation velocity of Bi-2212 superconducting phase. In this study we have focused on microhardness measurements to investigate the mechanical properties. Vickers microhardness, Young's modulus, fracture toughness and yield strength values are calculated separately for all samples. Experimental results of hardness measurements are analyzed using the some models. Finally, the Hays-Kendall model is determined as the most successful model describing the mechanical properties of our samples. © 2013 Springer Science+Business Media New York.
Changes in mechanical and structural properties of Bi-2212 added MgB2 superconductors
(2016-06-01) Koparan E.; Savaskan B.; Ozturk O.; Kaya S.; Aksoy C.; Wang J.; Speller S.; Grovenor C.; Gencer A.; Yanmaz E.
In the present study, we investigate the effects of Bi2Sr2Ca1Cu2O8+κ (Bi-2212) addition on structural and mechanical properties of bulk MgB2 obtained by hot-press method by means of X-ray diffraction, the Scanning Electron Microscopy and Vickers microhardness measurements. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 8 and 10 wt%) of the total MgB2. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano boron (B) powder and Bi-2212 powder which are produced by hot-press method. As a result of the hot-press process, the compact pellet samples were manufactured. The microhardness results were analyzed by Meyer’s law, Proportional Sample Resistance Model, Elastic–Plastic Deformation Model, Hays Kendall Approach, and Indentation Induced Cracking (IIC) Model. IIC model was identified as the most appropriate model for samples exhibiting the reverse indentation size effect behavior.
Characterization of the CoFe2O4/Cu displacement effect in the Y123 superconductor matrix on critical properties
(2020-11-01) Safran S.; Bulut F.; Nefrow A.R.A.; Ada H.; Ozturk O.
In this study, CoFe2O4 (x = 0, 5, 10 and 20 wt%) doped YBa2Cu3−x(CoFe2O4)xO7−δ bulk samples were produced using solid state reaction (SSR) method and sol–gel(SG) methods. Oxide-form and acetate-form powders were preferred for SSR method and SG method, respectively. The heat treatment of the produced samples was carried out in two stages. Firstly, the samples were annealed at 950 °C for 24 h, after which they were kept in oxygen at 500 °C for 5 h and allowed to be cooled down to room temperature. Characterization of all samples was performed using methods such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent resistance measurement (R–T) and Vickers microhardness analysis. Superconducting behavior was observed in all the produced samples, but as a result of the addition, a decrease was observed with the increase of the doping ratio at the critical transition temperature. As a result of the characterization, it is concluded that the doping ions can be replaced with Cu atoms in Y123 structure. In addition, doping led to significant changes in Vickers microhardness results.
Comparative study on mechanical properties of undoped and Ce-doped Bi-2212 superconductors
(2013-07-01) Zalaoglu Y.; Bekiroglu E.; Dogruer M.; Yildirim G.; Ozturk O.; Terzioglu C.
This study discusses the mechanical performances of Bi1.8Sr 2.0CexCa1.1Cu2.1Oy ceramics with x = 0, 0.001, 0.003, 0.005, 0.01, 0.03, 0.05 and 0.1 by way of Vickers microhardness (Hv) measurements performed at different applied loads in the range of 0.245-2.940 N. For the potential industrial applications, the important mechanical characteristics such as Vickers microhardness, elastic modulus, yield strength, fracture toughness and brittleness index values of the samples studied are extracted from the microhardness measurements. All the results obtained indicate that the Vickers hardness, Young's (elastic) modulus, yield strength, fracture toughness and brittleness index values suppress with the increment of the Ce concentration in the system as a consequence of the degradation in the connectivity between superconducting grains. The decrement in the Hv values with the applied load is attributed Indentation Size Effect behaviour of the samples studied. Moreover, the experimental results of Vickers microhardness measurements are estimated using the 5 different models such as Kick's law, proportional sample resistance model, modified proportional sample resistance model, elastic/plastic deformation model and Hays-Kendall approach. According to the results obtained from the simulations, Kick's law is not useful model to obtain information about the origin of the indentation size effect feature of the Ce-doped bulk Bi-2212 superconductors. On the other hand, the Hays-Kendall approach is determined as the most suitable model for the description of the mechanical properties of the superconducting samples. In addition, the bulk porosity analysis for the samples reveals that the porosity increases monotonously with the Ce inclusion in the Bi-2212, leading to the degradation of the grain connectivity. © 2013 Springer Science+Business Media New York.
Comparison of the Dopant Effect and Sample Preparation Method on Y-123 Superconductors
(2021-11-01) Ozturk O.; Nefrow A.R.A.; Bulut F.; Kurnaz S.; Safran S.
The detailed comparison of the effects of Co and CoFe2O4 dopants and preparation methods (solid-state reaction method and sol–gel methods) have been studied on structural, electrical, superconducting, and mechanical properties of Y123 bulk superconductors. The doping amounts of Co and CoFe2O4 were chosen up to 0.10 wt. %. X-ray powder diffraction (XRD) method, temperature-dependent resistance measurement (R-T), and Vickers microhardness analyses were performed to characterize prepared samples. XRD analysis showed that all samples have Pmmm symmetry of orthorhombic crystal structure; intensities and width of the diffraction lines were affected by doping material, but, independent of the preparation method. Although all samples crystallize in orthorhombic structure and exhibit superconductivity behavior, with increasing doping rate the critical transition temperatures of the samples showed a significant decrease and broadened to superconducting temperature transition width. This is more evident in CoFe2O4-doped Y-123 samples produced by sol–gel method. As the applied force increased, it was observed that the microhardness values of the Co-doped samples increased while the CoFe2O4-doped samples decreased, regardless of the sample preparation method.
Comparison of theoretical and experimental microhardness of tetrahedral binary Zn1-xErxO semiconductor polycrystalline nanoparticles
(2019-03-01) Asikuzun E.; Ozturk O.
Zn1−xErxO polycrystalline nanoparticles with various compositions (x=0.01,0.02,0.03,0.04,0.05, and 0.10)were prepared using sol–gel techniques, for which zinc acetate dihydrate and erbium 2–4 pentanedionate are used as precursors. Nanoparticles were pressed under a pressure of 4 tons for 5 min into disk-shaped compacts with 2 mm thicknesses and 10 mm diameters. The pressed samples were annealed at 400 °C for 30 min. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vickers microhardness analyses of the produced Er-doped ZnO bulk nanomaterials were performed. Specifically, in this study we focused on the analysis of their mechanical properties. Undoped and Er-doped bulk samples were investigated according to Meyer's law; the proportional sample resistance (PSR), elastic/plastic deformation (EPD), and indentation-induced cracking (IIC) models; and the Hays–Kendal (HK) approach. As a result, the IIC model was more suitable to determine the micromechanical properties and the reverse indentation size effect (RISE) behavior of Er-doped ZnO semiconductors.
Comparison of Vickers microhardness of undoped and Ru doped BSCCO glass ceramic materials
(2018-03-01) Ozturk O.; Asikuzun E.; Tasci A.; Gokcen T.; Ada H.; Koralay H.; Cavdar S.
In this study, effect of substitution ratio on the mechanical and structural properties of Bi1−xRuxPb0.2Sr2CaCu2O10+δ system, that is prepared in the ratios of x = 0.0, 0.025, 0.050, 0.075, is investigated. Samples are prepared with glass ceramic method and sintered at 845 °C. XRD and SEM measurements are performed for structural analyses, and Vickers micro-hardness measurements are carried out at different applied load (0.245 ≤ F ≤ 2.940 N) in order to investigate the mechanical performance of the Ru doped Bi1−xRuxPb0.2Sr2CaCu2O10+δ system. Experimental results of Vickers micro-hardness analyses are performed using the Meyer’s law, the proportional samples resistance model, the elastic/plastic deformation model, the Hays–Kendall approach and the indentation induced cracking (IIC) model. All analyses results are exhibited reverse indentation size effect behavior. The measured hardness values increase with increasing the applied load. Finally, IIC model is determined as the most successful model describing the mechanical properties of our samples.
Correlation between crystal defects and room temperature ferromagnetism of hydrothermally grown Eu substituted ZnO nanorods
(2022-11-15) Kaya S.; Ozturk O.; Arda L.
The hydrothermal method has been used to grow zinc oxide nanorods on a glass substrate with different Europium (Eu) concentrations. The Eu doping effect on the structural, optical, and magnetic properties of the samples was systematically investigated. The undoped sample exhibited diamagnetic behaviour, while soft room temperature ferromagnetism was observed in all the Eu substituted samples. With regard to the hysteresis loops, the highest coercivity, saturated magnetic moment, and retentive magnetic moment values were observed to be 41.64 Oe, 18.86 × 10−6 emu, and 2.17 × 10−6 emu, respectively, for ZnO:Eu 7%. According to the relationships between the magnetic properties, Eu doping levels, and defects concentrations, it can be concluded that the room temperature ferromagnetism observed in the samples is caused by crystal point defects including oxygen vacancies and zinc interstitials, rather than carrier-mediated exchange interactions, which is also consistent with the bound magnetic polarons theory.
Effect of annealing time on the structural, optical and electrical characteristics of DC sputtered ITO thin films
(2014-10-01) Senol S.D.; Senol A.; Ozturk O.; Erdem M.
Using an Indium tin oxide (ITO) ceramic target (In2O3:SnO2, 90:10 wt%), ITO thin films were deposited by conventional direct current magnetron sputtering technique onto glass substrates at room temperature. The obtained ITO films were annealed at 400 °C for different annealing times (1, 2, 5, 7, and 9 h). The effect of annealing time on their structural, optical and electrical properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microcopy (AFM), ultra violet–visible (UV–Vis) spectrometer, and temperature dependence Hall measurements. XRD data of obtained ITO films reveal that the films were polycrystalline with cubic structure and exhibit (222), (400) and (440) crystallographic planes of In2O3. AFM and Scanning Electron Microscopy SEM have been used to probe the surface roughness and the morphology of the films. The refractive index (n), thickness and porosity (%) of the films were evaluated from transmittance spectra obtained in the range 350–700 nm by UV–Vis. The optical band gap of ITO film was found to be varying from 3.35 to 3.47 eV with the annealing time. The annealing time dependence of resistivity, carrier concentration, carrier mobility, sheet resistance, and figure of merit values of the films at room temperature were discussed. The carrier concentration of the films increased from 1.21 × 1020 to 1.90 × 1020 cm−3, the Hall mobility increased from 11.38 to 18 cm2 V−1 s−1 and electrical resistivity decreased from 3.97 × 10−3 to 2.13 × 10−3 Ω cm with the increase of annealing time from 1 to 9 h. Additionally, the temperature dependence of the carrier concentration, and carrier mobility for the as-deposited and 400 °C annealed ITO films for 2 and 9 h were analysed in the temperature range of 80–350 K.
Effect of boron doping on the structural, optical and electrical properties of ZnO nanoparticles produced by the hydrothermal method
(2015-11-01) Senol S.; Ozturk O.; Terzioğlu C.
The effect of boron doping with 0–11 at% concentration on structural, optical and electrical properties of zinc oxide nanopowder synthesized by a hydrothermal method has been reported. We have performed X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), optical, Hall and resistivity measurements on the samples. XRD results reveal that all B doped ZnO nanopowders have single phase hexagonal (Wurtzite) structure without any impurity. But the positions of main diffracted peaks of ZnO shifted slightly towards small (2θ) angle and grain size decreases from 60.75 nm to 34.34 nm with an increase of B doping concentrations. SEM analysis indicates that the doping concentration of B affected the surface morphology of ZnO nanostructures. Optical properties were examined by UV–vis absorption/diffuse reflectance spectroscopy. The optical band gap of Zn1−xBx O nanostructures increased from 3.27 eV to 3.30 eV with increasing doping from x=0 to x=0.11. The role of doping concentrations of B on the transport properties was searched by temperature dependent Hall measurements in 180–350 K temperature range. The carrier concentration of the samples increased from 0.11×1014 cm−3 to 4.08×1014 cm−3, the Hall mobility decreased from 5.61 cm2 V−1 s−1 to 1.22 cm2 V−1 s−1 and electrical resistivity decreased from 10.89×104 Ω cm to 1.25×104 Ω cm with the increase of the B doping concentrations at room temperature. The electrical resistivity is observed to decrease with both the increase in dopant concentration and the temperature in the range of 180–350 K.
Effect of Ce addition on the magnetoresistivity, irreversibility field, upper critical field and activation energies of Bi-2212 superconducting ceramics
(2012-05-01) Yildirim G.; Dogruer M.; Ozturk O.; Varilci A.; Terzioglu C.; Zalaoglu Y.
This study aims to analyze the effect of Ce addition on the microstructural, superconducting and physical properties of Bi 1.8Sr 2.0CexCa 1.1Cu 2.1O y ceramics with x = 0, 0.001, 0.003, 0.005, 0.01, 0.03, 0.05 and 0.1 via X-Ray analysis (XRD), scanning electron microscopy (SEM), electron dispersive X-Ray (EDX) and magnetoresistivity measurements. The ceramics produced in this work are prepared using the standard solid-state reaction method. The zero resistivity transition temperatures (T c), activation energies (U0), irreversibility fields (μ 0Hi rr) and upper critical fields (μ 0H c2) are determined from the resistivity versus temperature (R-T) curves under dc magnetic fields up to 7 T The results show that T c and U0 values of the samples are found to decrease dramatically with the increase in the Ce-content and applied magnetic field. Moreover, XRD results indicate that all the samples contain the Bi-2212 phase only and exhibit the polycrystalline superconducting phase with less intensity of diffraction lines with the increase of the Ce addition. As for the results of SEM images, the texturing, crystallinity, grain size distribution, layered grain growth and grain connectivity are observed to degrade with the increase of the Ce doping. Besides, the irreversibility fields and upper critical fields are found to degrade as Ce doping increases. Penetration depths (λ) and coherence lengths (ξ) are also discussed. © 2012 Springer Science+Business Media, LLC.
Effect of Co/Cu partial replacement on fundamental features of Y-123 ceramics
(2020-05-01) Ozturk O.; Nefrow A.R.A.; Bulut F.; Ada H.; Turkoz M.B.; Yildirim G.
This study is liable for the effect of sample production processes including the standard solid-state reaction (SSR) and classical sol–gel (SG) preparation methods on the fundamental characteristic features, namely electrical, superconducting, crystal structure quality, crystallinity, morphological, strength quality of grain boundary couplings, and interaction between the grains of YBa2Cu3−xCoxO7−δ (Y-123) advanced ceramic compounds within the weight ratio intervals x = 0–20%. The main heat treatments are exerted at two main steps: (I) annealing at 950 °C for 24 h in air medium conditions and (II) annealing at 500 °C during 5 h under the oxygen annealing ambient. The standard measurement methods such as powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent electrical resistance, and Vickers hardness measurements are performed for the characterization of materials. It is found that the samples prepared at SSR route present much more superior characteristic features as compared to those fabricated at SG technique, being one of the most striking points deduced this work. In more detail, every material prepared crystallizes in the orthorhombic symmetry and exhibits the superconducting nature but considerable decrement in the critical transition temperatures. The onset and offset transition temperatures are noted to decrease regularly from 92.96 K (92.28 K) to 90.20 K (83.59 K); and 90.05 K (90.03 K) to 45.97 K (30.49 K) for the materials prepared by the SSR (SG) route. Similarly, the variation in the lattice cell and average grain size parameters confirm that the Co/Cu substitution damages Y-123 superconducting phase. Additionally, the Co/Cu partial replacement mechanism leads to increase significantly the Vickers hardness results. To sum up, the Co/Cu partial substitution (produced by either SSR or SG method) is plowed to improve the fundamental characteristic features for new, novel, and feasible market application areas of Y-123 cuprate ceramics in the universe economy.