Breaking point of the harmony between Gd diffused Bi-2223 slabs with diffusion annealing temperature

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–O₂ 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.     

Increased homogenous clusters in superconducting paths with diffusion of optimum Ni impurities into Bi-2223 crystal

This study deals with variations of electrical and superconducting features of Bi-2223 superconducting materials exposed to Ni impurity diffusion at different annealing temperatures (650 °C?≤?T?≤?850 °C) by temperature-dependent resistivity measurements. It is found that the characteristic properties improve with annealing temperature up to 700 °C as a result of enhancement in the truly-metallic characteristics, interaction quality, formation of Cooper-pairs and overlapping of Cu-3d and O-2p wave functions. Similarly, the optimum annealing temperature of 700 °C diminishes the omnipresent flaws and structural defects. Additionally, we design a strong theory (Percolation) to discuss the role of nickel impurities on fundamental aspects of material science and physical quantities as regards stabilization of superconductivity in the homogeneous regions and formation of superconducting clusters in the paths for the first time. Further, we develop an empirical relationship between the structural problems and transition temperatures to obtain a superconductor exhibiting the highest electrical and superconducting features.     

The Effect of Sintering Temperature in Bi1.7Pb0.2Sb0.1Sr2Ca2Cu3O y Superconductors

In this study, the effects of sintering temperature on the Bi-2223 phase formation and the influence of minor phases on the intergranular properties of Sb substituted Bi-2223 samples were investigated. The samples were prepared by solid-state reaction method with different sintering temperatures ranging from 800 to 855 °C. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and density measurements. We observed the optimal temperature of the Sb + Pb substituted Bi-2223 system as 845 °C.     

Physical Properties and Diffusion-Coefficient Calculation of Iron Diffused Bi-2223 System

This study includes two parts: (I)?investigation of the effect of different annealing time (10?h, 30?h, and 60?h) on physical, superconducting, and microstructural properties of Fe-diffused Bi-2223 superconductor ceramics prepared by the conventional solid-state reaction method with the aid of the X-ray diffraction (XRD), scanning electron microscopy (SEM), dc resistivity (???CT) and transport critical current density (J _c ) measurements, and (II) determination of the diffusion coefficient and the activation energy of iron in the Bi-2223 system. In the former part, the zero-resistivity transition temperature (T _c ), phase purity, volume fraction, hole-carrier concentration, lattice parameters, surface morphology, texturing, crystallinity, grain connectivity, grain size, and room temperature resistivity values of the bulk samples are found and compared with each other. The results obtained show that both the zero resistivity transition temperature (T _c ) and transport critical current density (J _c ) regularly enhance with the increment in the diffusion-annealing time. The maximum T _c of 107±0.2 K and J _c of 50.0?A?cm^?2 are observed for the sample annealed at 830?°C for 60?h. As for the XRD investigations, according to the refinement of cell parameters done by considering the structural modulation, the enhancement in the diffusion-annealing is confirmed by both a decrease of the cell parameter a and an increase of the lattice parameter c of the samples, meaning that the greatest Bi-2223 phase fraction belongs to the sample annealed at 830?°C for 60?h. Moreover, SEM images display that the sample has the best crystallinity, grain connectivity, and largest grain size. Based on the results, the superconducting and microstructural properties improve with the increase in the diffusion-annealing time. In the latter part, Fe diffusion in the Bi-2223 system is examined in a range of 500?C830?°C by the variation of the lattice parameters evaluated from the XRD patterns. The temperature dependence of the Fe diffusion coefficient is described by the Arrhenius relation D=4.27×10^?5exp(?1.27±0.10) eV/k_BT, and the related activation energy of the iron in the Bi-2223 system is found to be about 1.27?eV. The relatively low value of activation energy obtained illustrates that the migration of the Fe ions primarily proceeds through defects such as pore surfaces and grain boundaries in the polycrystalline structure, leading to the improvement of the microstructural and superconducting properties of the samples, supported by the results of part?I. All in all, the aim of the present study is not only to analyze the role of diffusion-annealing time on superconducting and microstructural properties of Fe-diffused Bi-2223 superconductors, but also to find the diffusion coefficient and activation energy of Fe in the Bi-2223 system.     

Influence of Diffusion-Annealing Temperature on?the?Physico-Mechanical Properties of Au-doped Bi-2223 Superconductors

In order to investigate the influence of Au doping and diffusion-annealing temperature on the mechanical and superconducting properties of Bi-2223, Bi_1.8Pb_0.35Sr_1.9Ca_2.1Cu₃O _y superconductors were prepared by standard solid-state reaction methods. Doping of Bi-2223 was carried out by means of gold diffusion during sintering from an evaporated gold film on pellets. The investigation consisted of scanning electron microscopy, dc resistivity and hardness measurements. Electrical-resistivity measurements indicated that the room-temperature resistivity value decreased with decreasing diffusion-annealing temperature from 830 to 500?°C and these samples (G830, G800, G750, G700, G600 and G500) show the resistive behavior above the onset critical transition temperature with the zero-resistivity transition temperatures of 104 K, 80 K, 98 K, 95 K, 102 K and 103 K, respectively. To investigate mechanical properties of the samples, we have measured the diagonal length as a function of test load in the range of 0.245?C2.940 N. Mechanical properties (microhardness, Young??s modulus, yield strength and fracture toughness) of the samples are found to be load and diffusion-annealing temperature dependent. In addition, we have calculated the load independent hardness, Young??s modulus, yield strength, and fracture toughness of the samples. The possible reasons for the observed changes in superconducting and mechanical properties due to Au diffusion and diffusion-annealing temperature were discussed.     

Role of annealing time and temperature on structural and superconducting properties of (Bi,Pb)-2223 thin films produced by sputtering

This study reports the effect of annealing time (15 min, 1.5 and 3 h) and temperature (850, 860 and 870 °C) on the structural and superconducting properties of thin films by means of scanning electron microscopy (SEM), X-Ray analysis (XRD), electron dispersive X-Ray (EDX), resistivity and transport critical current density (J_c) measurements. Zero resistivity transition temperatures (T_c) of the films produced are estimated from the dc resistivity measurements. In addition, the phase and lattice parameters are determined from XRD patterns when the microstructure, surface morphology and element composition analyses of the samples are investigated by SEM and EDX measurements, respectively. The results indicate that T_c values of the films obtained are observed to be in a range of 23–102 K. The T_c of the film annealed at 870 °C for 3 h is found to be the smallest (23 K) while the film annealed at 860 °C for 3 h is noted to obtain the maximum T_c value (102 K). On the other hand, the maximum (minimum) J_c is found to be about 2068 A/cm² (20 A/cm²) for the film annealed at 860 °C for 3 h (870 for 3 h). Moreover, according to the refinement of cell parameters done by considering the structural modulation, the greatest Bi-2223 phase fraction is noticed to belong to the film annealed at 860 °C for 3 h. Furthermore, SEM measurements show that the best surface morphology, largest grain size and grain connectivity are observed for that film. Based on these results, T_c and J_c values of the samples studied are found to depend strongly on the microstructure. As for EDX results, the elements used for the preparation of samples are observed to distribute homogeneously. The aim of this study is not only to investigate the changes of structural and superconducting properties of the films produced in the varied time and temperature but also to determine the best ambient for the film fabrication and show the feasibility of obtaining Bi-2223 film with tailored structure.     

The influence of electroplastic rolling on the mechanical deformation and phase evolution of Bi-2223/Ag tapes

Electroplastic rolling (EPR) of Bi-2223/Ag superconducting wires was performed, where pulse currents were applied during rolling to introduce an electroplastic effect. It was found that the rolling force decreased significantly compared with the traditional rolling process. Furthermore, EPR favorably minimized the sausage effect. It is revealed that the electroplastic effect can facilitate the mechanical deformation of Bi-2223/Ag composites. Segments of the Bi-2223/Ag tapes were heat treated at 830 °C for different time periods. The phase assemblies of these samples suggest that current pulses contribute to faster transformation kinetics from the Bi-2212 phase to the Bi-2223 phase. In addition, a preliminary improvement of 28% of critical current density has been achieved in a fully processed tape with EPR.     

Microstructure and Superconducting Properties of TaC-Doped Bi-2223 Ceramics

The microstructure, phase composition, and superconducting properties of Bi-2223 ceramics doped with 0.05–0.5 wt % TaC were investigated. The materials were heat-treated at 840°C in three steps (10 + 24 + 24 h). By optimizing the TaC content and heat-treatment conditions, the 77-K critical current density of the Bi-2223 ceramics in zero field was raised by a factor of 2.     

Low temperature synthesis of sol–gel derived Al-doped ZnO thin films with rapid thermal annealing process

A series of sol–gel derived Al-doped ZnO (AZO) thin films with rapid thermal annealing process at low temperature were studied to examine the influence of annealing temperature and the Al doping concentration on their microstructure, electrical and optical transport properties. Crystalline AZO thin films were obtained following an annealing process at temperatures between 400 and 600 °C for 10 min in argon gas ambient. AZO thin films with Al doping of 1 at% were oriented more preferentially along the (002) direction, and have larger grain size and lower electrical resistivity, while the highest average optical transmittances of 92% were observed in AZO films with Al doping of 2 at%. With the annealing temperature increasing from 400 to 600 °C, the grain size of AZO films increased, the optical transmittance became higher, and the electrical resistivity decreased to a lowest value of 1.2 × 10⁻⁴ Ω cm resulting from the increase of the carrier concentration and the mobility.     

Change of formation velocity of Bi-2212 superconducting phase with annealing ambient

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 (H_v) 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.     

Effect of annealing temperature on electrical and nano-structural properties of sol–gel derived ZnO thin films

Zinc oxide (ZnO) thin films have been prepared on silicon substrates by sol–gel spin coating technique with spinning speed of 3,000 rpm. The films were annealed at different temperatures from 200 to 500 °C and found that ZnO films exhibit different nanostructures at different annealing temperatures. The X-ray diffraction (XRD) results showed that the ZnO films convert from amorphous to polycrystalline phase after annealing at 400 °C. The metal oxide semiconductor (MOS) capacitors were fabricated using ZnO films deposited on pre-cleaned silicon (100) substrates and electrical properties such as current versus voltage (I–V) and capacitance versus voltage (C–V) characteristics were studied. The electrical resistivity decreased with increasing annealing temperature. The oxide capacitance was measured at different annealing temperatures and different signal frequencies. The dielectric constant and the loss factor (tanδ) were increased with increase of annealing temperature.     

Microstructure and properties of Al-doped ZnO thin films by nonreactive DC magnetron sputtering at room temperature following rapid thermal annealing

A series of Al-doped ZnO (AZO) thin films deposited by nonreactive DC magnetron sputtering at room temperature following rapid thermal annealing was studied to examine the influence of these Al doping concentration, sputtering power and annealing temperature on their microstructure, electrical and optical transport properties. AZO thin films with Al dopant of 3 wt% were oriented more preferentially along the (002) direction, bigger grain size and lower electrical resistivity The resistivity of AZO films decreases with the increase of Al content from 1 to 3 wt%, sputtering power from 60 to 100 W and the annealing temperature from 50 to 250 °C. Sputtering power and annealing had some effect on the average transmittance of AZO thin films. For AZO thin films with Al doping level of 3 wt%, the lowest electrical resistivity of 5.3 × 10⁻⁴ Ω cm and the highest optical transmittance of 88.7% could gain when the sputtering power was 100 W and the annealing temperature was 200 °C or above.     

High thermal stability of AlCrTaTiZr nitride film as diffusion barrier for copper metallization

To inhibit rapid Cu diffusion in interconnect structures, an effective diffusion barrier layer with high thermal stability, low electrical resistivity and good interface adhesion is strongly demanded. Thus in this study, an amorphous nitride film of equimolar AlCrTaTiZr alloy with an N content of about 41 at.% was deposited by reactive radio-frequency magnetron sputtering. Thermal stability of the AlCrTaTiZr nitride film and its barrier property to Cu diffusion were investigated under thermal annealing at 700-900 °C. The AlCrTaTiZr nitride film remained an amorphous structure after thermal annealing at 700 °C and then crystallized at 800 °C. However, no interdiffusion between Si substrate and Cu metallization through the AlCrTaTiZr nitride film occurred. The electrical resistivity of the film remained at the low level of as-deposited value, indicating its good thermal stability as an effective diffusion barrier layer. With temperature further increasing to 900 °C, severe interdiffusion occurred, along with the formation of silicides and large pores. The electrical resistivity then significantly increased, implying the failure of the AlCrTaTiZr nitride film.     

Precipitation Processes in Al-Mg-(Mn,Cu) Type Alloy Sheets Evaluated Through Electrical Resistivity Variations

Precipitation/dissolution processes were followed by electrical resistivity variations in Al-Mg-(Mn)-Cu and Al-Mg-Mn type alloy sheets after different thermo-mechanical treatments (TMTs). In order to get an insight into the precipitation processes during processing of Al-Mg type alloys, some samples were solution treated at 535°C/1 h, and some of them were recrystallization annealed at 320°÷350°C/3 h. After that all the samples were treated in a same manner: cold rolling to 50–60% and final annealing at temperatures in the range of 220°÷470°C/3 h. It was supposed that the structure of samples pre-treated by recrystallization annealing at 320°/350°C is characterized with S type (Al₂MgCu) phases in the Al-Mg-(Mn)-Cu alloys and with β′/β (Mg₅Al₈) phases in the Al-Mg-Mn alloys. These structure features are rather unchangeable during the subsequent cold rolling and annealing treatments in the temperature range of 220°÷320°C. During annealing at higher temperatures (such as 470°C) precipitation of Mn-bearing particles (MnAl₆ or (Fe,Mn)Al₆) might occur in both type of alloys. After solution treatment at 535°C most of the alloying elements are dissolved into solid solution, thus inducing a high potential for precipitation processes during annealing at 220°÷470°C. The cold deformation was found to contribute the electrical resistivity intensively at the beginning of deformation (in the range up to ∼20%), and it was not influenced by the chemical composition of tested alloys. The resistivity variations with the cold deformation were fitted by power-law equations.     

Influence of preparation conditions on superconducting properties of Bi-2223 thin films

We report electrical transport properties of Bi₂Sr₂Ca₂Cu₃O_10+x (Bi-2223) superconducting thin films fabricated by pulsed-laser deposition on SrTiO₃ substrate. The aim of the study was to investigate the influence of preparation conditions such as deposition temperature (T _S), annealing time (t _A) and deposition rate (r). A critical temperature (T _c) as high as 110 K and critical current density (J _c) of 6·2 × 10⁶ A/cm² at 20 K were obtained for T _S = 760°C, t _A = 4 h and r = 1·5 Å/s. We also investigated the effect of Li doping on Bi-2223 thin films. Li intercalation results in high resistive onset transition temperature and the resistivity shows broadening in magnetic field that increases with field. The large broadening of resistivity curve in magnetic field suggests that this phenomenon is directly related to the intrinsic superconducting properties of the copper oxide superconductors. The sudden drop in J _c at relatively low magnetic field (H < 0·5 tesla) is due to the effect of Josephson weak-links at the grain boundaries.     

Effects of annealing process on microstructure and electrical properties of cold-drawn thin layer copper cladding steel wire

The microstructure, mechanical and electrical properties of cold-drawn thin layer copper cladding steel (CCS) wires annealed after different processes were studied by optical microscopy, electron omnipotent material experiment machine, micro hardness machine, SEM and electrical resistivity measurement system. The results indicated that the recovery and recrystallization of steel-core happened in the temperature range 550–750 °C for the holding period of 120 min. When the annealing temperature was higher than 750 °C, grains begun to grow and grain sizes increased gradually with increasing the annealing temperature. The tensile strength and micro hardness were declined with increasing annealing temperature and holding time. The distance of Cu–Fe atoms interfacial diffusion of thin layer CCS wires ranged from 4 µm of cold-drawn wire to 7.5 µm of annealed wire at 850 °C for 120 min. The higher the annealing temperature become, the larger the distance of Cu–Fe atoms interfacial diffusion is. When the annealing temperature was lower than 650 °C, the resistivity was slightly less than 71 × 10^?3 Ω mm² m^?1 which was the resistivity of cold-drawn wire. When the annealing temperature was higher than 650 °C, the resistivity increased with increasing the annealing temperature. Meanwhile, the variation of electrical property of thin layer CCS wires was analyzed and discussed based on microstructure and interfacial diffusion.     

Some physical properties and Vickers hardness measurements of Fe diffusion-doped Bi<Subscript>1.8</Subscript>Pb<Subscript>0.35</Subscript>Sr<Subscript>1.9</Subscript>Ca<Subscript>2.1</Subscript>Cu<Subscript>3</Subscript>O<Subscript>y</Subscript> superconductors

In this study we have investigated the influence of iron diffusion and diffusion-annealing time on the mechanical and the superconducting properties of bulk Bi_1.8Pb_0.35Sr_1.9Ca_2.1Cu₃O_y superconductors by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness, dc resistivity (ρ-T) and critical current density (J_c) measurements. The samples are prepared by the conventional solid-state reaction method. Doping of Bi-2223 was carried out by means of iron diffusion during sintering from an evaporated iron film on pellets. Then, the Fe layered superconducting samples were annealed at 830 °C for 10, 30 and 60 h. The mechanical properties of the compounds have been investigated by measuring the Vickers hardness (H_v). The mechanical properties of the samples were found to be load dependent. The load independent Vickers hardness (H₀), Young’s modulus (E), yield strength (Y), and fracture toughness (K_IC) values of the samples are calculated. These all measurements showed that the values of the Vickers hardness, critical current density, and critical transition temperature and lattice parameter c increased with increasing Fe doping and diffusion-annealing time.     

The Effects of Mg Substitution in Bi-2223 Superconductors

The effects of Mg substitution in Bi-2223 superconductor system has been studied for the Bi_1.7Pb_0.3Sr₂Ca₂Cu_3−x Mg _x O _y nominal composition (x=0.00, 0.05, 0.10, 0.15 and 0.20) which was prepared by the conventional solid-state reaction. The properties of these compounds have been investigated by measuring the electrical resistivity, X-ray diffraction (XRD) and density. Also, scanning electron microscopy (SEM) was employed to investigate the surface microstructure of the samples. It has been found that the effects of Mg substitution support the development of both the Bi-2212 and Bi-2223 phases. These measurements and analyses enable us to discuss the effects of Mg dopant on superconducting properties. We found that onset critical temperatures (T _c, onset) decrease with addition x>0.10 in resistivity measurements. The presence of Mg influenced the microstructure of the samples and decreased the mean grain size of Bi-2223 grains up to x=0.10.     

Preparation and high-temperature tribological properties of CrAlVYN-Ag nanocomposite coatings

CrAlVYN-Ag coatings were successfully deposited by introducing the elements of V and Ag into CrAlYN hard coatings. Their microstructure and mechanical property as a function of the annealing temperature were investigated from room temperature (RT) (～25°C) to 800°C. Besides, the worn surfaces were analyzed after combined effects of temperature and friction to figure out the wear mechanisms at different temperatures. The coatings exhibited special surface morphologies and Ag diffusion after annealing at different temperatures. In addition, the x-ray diffraction results showed that the coatings suffered obvious oxidation once the temperature exceeded 600°C; as a result of this, the coating hardness decreased sharply. The friction coefficients were relatively high during the tribological tests from RT to 400°C because the abrasive wear mechanisms played a dominant role. The lower friction coefficients obtained at 600 and 700°C were mainly due to the self-lubricating mechanisms. However, the coating exhibited higher friction coefficient at 800°C, which was mainly ascribed to the severe oxidation wear of the coating.     

Effects of annealing temperature and thickness on microstructure and properties of sol–gel derived multilayer Al-doped ZnO films

Transparent conductive multilayer Al-doped ZnO (AZO) films were prepared by the spin-on technique with rapid thermal annealing process at low temperature. The effects of annealing temperature and thickness on microstructure, growth behavior, electrical properties and optical properties of AZO films were investigated. It was found that AZO films exhibited stronger preferred c-axis-orientation, the electrical resistivity decreased as it would be expected with the increase of annealing temperature from 400 to 500 °C and the increase of the number of layers in the film from 1 to 6, but the electrical resistivity tended to keep at a certain lowest value of 2.7 × 10⁻⁴ Ω cm when the annealing temperature was above 500 °C and the number of layers did not exceed 6. The average optical transmittance of AZO films was over 90% when number of layers in the film did not exceed 4 and decreased as this number increases, but the annealing temperature had little effect on the average optical transmittance of AZO films.