Tc Zero Research Articles

Synthesis of Superconductor Bi1,6Pb0,4Sr2Ca2Cu3O(10+x) for Meissner Test Demonstration Using Solid Reaction Method

The research has been done in the field of Field Work Practice to synthesize superconductors Bi1,6Pb0,4Sr2Ca2Cu3O10+x for Meissner test using solid reaction method. The objective of this research is to make superconductor Bi1,6Pb0,4Sr2Ca2Cu3O10 x with solid reaction method and to know the result of superconducting character of Bi1,6Pb0,4Sr2Ca2Cu3O10 +x based on Meissner test. From the results of Meissner test that has been done on this superconductor sample looks super magnet and superconductor repel each other rejects or super magnet drift.Sehingga it can be concluded that the sample has a strong Meissner effect. From the results of Tc test using cryogenic tools obtained Tc Zero temperature of 103.4 K and Tc Onset of 116.67 K. From the data obtained it can be concluded that the sample has reached phase 2223.

Superconducting Joint of GdBa2Cu3Oy Coated Conductors by Crystallization of an Additionally Deposited Precursor Layer

A superconducting joint of REBa 2 Cu 3 O y (REBCO) coated conductors (CCs) has been demanded strongly to fabricate long length CCs for high field magnet applications such as nuclear magnetic resonance and magnetic resonance imaging. In the previous reports of superconducting joint, specimens of REBCO CCs were jointed via melting REBCO phases or via solid state diffusion of REBCO phases. In our study, we propose a new method of joint for REBCO CCs. A precursor layer is additionally deposited on GdBCO CC by a metal organic deposition process, and then two pieces of them are stuck together face-to-face and crystallized the precursor to form 123 phase under mechanical pressure in an oxygen atmosphere. The microstructures and temperature dependence of resistance of the jointed sample are characterized by a cross-sectional transmission electron microscopy (TEM) and a four-probe method, respectively. As a result, TEM observation reveals that two CCs are jointed together without formation of secondary phases at the joint interface. Also, temperature dependence of resistance shows Tc onset and Tc zero of 93 K and 82 K, respectively. Consequently, a superconducting joint has been completed successfully. The concept of this method is combining film growth and solid-state diffusion for the additionally deposited precursor layers.

Preparation of Tl-2212 Cr-Substituted (Tl2-xCrx)Ba2CaCu2O8-δ Superconductor

We have prepared Tl2-xCrx)Ba2CaCu2O8-δ (Tl-2212) for x = 0.0-0.4 by standard solid state reaction with carbonate precursor and Cr2O3 as a source of Cr. The role of Cr substitute the Tl-sites in Tl-2212 superconductor system has been studied. The dc electrical resistance was determined using four point probe and the phase occurrence was studied by X-ray diffraction method. The transition temperature showed metallic normal state behavior for all samples. It was found that the addition of 0.2% mole Cr enhanced the Tc zero for 3.22%, whereas Tconset was enhanced up to 10.47%. The effectiveness substitution of Tl-sites by Cr was achieved in the series of x < 0.2%. Most of the samples were in 14/mmm space group.

Fabrication of SS316-Sheathed BPSCCO Superconducting Wire with the Addition of Carbon Nanotubes

This study aimed to determine the effects of using SS316 as a sheath of BPSCCO superconducting wire with the addition of 5 wt% carbon nanotubes. The method used in this research was powder in the tube (PIT), which consisted of several steps; namely preparation of precursors (Bi2O3, SrCO3, CaCO3, CuO2, PbO2, and carbon nanotube powder); manual mixing precursors using mortar agate for 3 hours; compaction of precursors in tubes; rolling the wire with the diameter up to 5 mm; calcinations at 820 °C for 20 hours; and sintering at 850 °C with time variation of 30 and 9 hours. The characterization was performed using cryogenic magnet to determine the value of critical temperature (Tc), SEM-EDX to analyze morphology, and XRD to discover the phase formed. From the research, it was found that the use of SS316 as a sheath for BPSCCO superconducting wire with the addition of 5 %wt carbon nanotubes affected the Tc. The system only produced the Tc onset of 100 K for the sample sintered for 30 hours, whereas the Tc zero was not produced.

Effect of Antimony (Sb) Substitution on Ba-Site of Porous Structured YBA2Cu3Oδ Superconductor

The effect of antimony (Sb) substitution on Ba-site of porous structure YBa2Cu3Oδ (YBCO) superconductor was investigated. Polycrystalline sucrose was used to create the open pores in the structure. A series of sample with a nominal composition of YBa2-xSbxCu3Oδ where x = 0.05, 0.10, 0.15, 0.20, 0.30, 0.40 and 0.50 were synthesized and characterized using X-ray diffraction (XRD) method, resistivity measurement technique and Scanning Electron Microscopic (SEM) equipment. For porous Sb-doped sample with x ≤ 0.30, the samples showed metallic behavior above onset critical temperature (TC onset) while semiconducting behavior was shown for x ³ 0.40. The optimum Sb concentration was achieved at x = 0.15, where TC zero is 85 K and critical current (JC) value measured at 70 K is 2.75 A/cm2. TC onset and TC zero of the sample were suppressed towards higher Sb concentration. High level of Sb concentration resulted in the non-superconducting sample and Sb was not incorporated properly into YBCO system. Generally, the crystallographic structure with 123 phase remains as orthorhombic. But, for Sb doping at x = 0.30, the sample exhibits tetragonal structure before the presence of 211 phase with the higher Sb concentration. SEM micrograph for porous sample showed the less dense packing with irregular grain shape compared to the standard sample where the small rounded particles grains that can be clearly seen. It can be summarized that the superconducting properties were attributed mainly by the dopants compared to the porous characteristic.

Electrical Properties of Li Substituted (Tl0.85Cr0.15)Sr2-xLixCaCu2O7 Superconductor

The effects of Li substitution for Sr in (Tl0.85Cr0.15)Sr2-xLixCaCu2O7 (Tl-1212) with x = 0 - 0.10 were investigated. Tl-1212 superconductor pellets were prepared via solid-state reaction and precursor method. The samples were characterized by x-ray diffraction and four-point probe methods. The XRD patterns showed that all samples formed mixed phases of Tl-1212 and Ca0.3Sr0.7CuO2 (CSCO). The temperature-dependent resistance measurements showed metallic-behavior for all samples with onset transition temperature, Tc onset between 96 K and 105 K and zero resistance temperature, Tc zero between 85 K and 94 K. The transition-width, ΔTc of all samples was in the range of 4 K to 11 K. The x = 0.02 and 0.07 sample showed increase in Tc onset to 105 K and 102 K, respectively. This work showed that Li improved the transition temperature for x = 0.02 and 0.07 samples although the dominant phase was not Tl-1212.

Effect of Eu Substitution in Low Density Bi (Pb)-2223 High Temperature Superconductors

High temperature superconductor ceramic of low density Bi1.6Pb0.4Sr2(Ca2-xEux)Cu3Oy both doped and non-doped, have been produced by the method of conventional solid state reaction synthesis. The effects of rare earth doping on the low density superconducting compound have been studied by considering Eu substitution at Ca site to stoichiometric of Bi (Pb)-2223 with x ranging from 0.000 to 0.2000. The experimental works in this study consist of direct-current (DC) electrical resistance-temperature and critical current density measurements for both electrical and superconducting properties, and powder X-ray diffraction (XRD) for phase analyses and lattice parameters while Field Emission Scanning Electron Microscopy (FESEM) for surface morphology. All the Eu-doped samples consist of both low-Tc Bi (Pb)-2212 and High-Tc Bi (Pb)-2223 phases. The substitution of Eu at the Ca site induced the decrease of volume fraction for the Bi (Pb)-2223 phase and the increase of the volume fraction for Bi (Pb)-2212 phase. Eu doping does not enhance the Tc zero but gradually decrease its value and become semiconducting at higher dopant concentration with x=0.200. From FESEM investigation, the grain size started to degrade from x=0.000 to x=0.0100 and form smaller plate-like grain which belong to Bi (Pb)-2212 phase and the grain particles are seem to be coagulated to form clusters for x=0.200.

Synthesis and Characterization of Low Density Bi-2223 Superconductors via Co-Precipitation Method

High temperature Bi1.6Pb0.4Sr2Ca2Cu3Oδ of low density has been synthesized via co-precipitation method and its electrical and structural properties have been studied. The optimum porosity of the samples was obtained using variety amount of sucrose C12H22O11 which is used as supplementary filler. The electrical properties of superconductor such as critical temperature, Tc and critical current density, Jc were determined using the four-probe method. X-ray diffraction (XRD) was used to analyze the structural properties of the samples. The density of samples was measured using densitometer. The obtained results have revealed a significant influence of the pore presence in superconducting samples on the electrical properties. The Tc for low density Bi-2223 with 0.1g sugar sucrose is much higher compared to 0.05g, 0.15g and standard sample which is Tc zero is 98 K. The Jc for low density Bi-2223 with 0.1g sugar sucrose is 6 A/cm2 at 60 K which is higher than high density samples. The crystallographic structure remains in the tetragonal form where a=b≠c for all samples.

Effects of Cd2+ substitution on elastic properties and step-like anomalies in Tl0.9Bi0.1Sr1.8Yb0.2Ca1−xCdxCu1.99Fe0.01o7−δ superconductors

Cd-doped Tl0.9Bi0.1Sr1.8Yb0.2Ca1−xCdxCu1.99Fe0.01O7−δ (x=0–0.4) bulk superconductor samples were prepared by solid-state reaction method, to examine the effect of Cd on ultrasonic velocity and elastic behavior of the samples. The samples were characterized by X-ray diffraction, DC electrical resistivity and temperature dependent ultrasonic velocity measurements. DC electrical resistivity measurement showed all the samples exhibit metallic normal-state behavior with the highest Tc zero observed at around 76.4K (x=0.3). Ultrasonic velocity measurements at 80K showed a non-linear increase in both absolute longitudinal and shear velocities as well as elastic moduli with Cd substitution with the largest increase observed for the x=0.3 sample. Temperature dependant longitudinal modulus showed elastic anomaly characterized by a step-like slope change at around 230K for x=0 &x=0.3 and at around 250K for x=0.4 with the x=0.3 sample showing the sharpest slope change. A comparison between experimental data and calculated lattice anharmonicity curve based on the model proposed by Lakkad, showed large deviation of the experimental longitudinal modulus curves for (x=0.3) from the calculated anharmonicity curves indicating that the elastic behavior was strongly influenced by the existence of the step-like longitudinal anomaly. On the other hand, our analysis using the Landau free energy model found that the anomalous step-like elastic behavior fitted well with the equation derived from the model for regions below and above the elastic anomaly temperature, TA. The fitting indicated that the anomaly is related to a phase transition that is suggested to involve ordering of oxygen which introduces strain in the system.

Effect of Yb Substitution in Bi&lt;sub&gt;1.6&lt;/sub&gt;Pb&lt;sub&gt;0.4&lt;/sub&gt;Sr&lt;sub&gt;2&lt;/sub&gt;Ca&lt;sub&gt;2-&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Yb&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;&lt;i&gt;y&lt;/i&gt;&lt;/sub&gt; Superconductor

This paper reports on the results of Yb substitution for Ca on the superconductivity and structural properties of Bi1.6Pb0.4Sr2Ca2-xYbxCu3Oy superconducting samples with x = 0.000, 0.025, 0.050, 0.100 and 0.200 which prepared by coprecipitation (COP) method. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron (FESEM), electrical and resistivity measurement by four-probe method. It was found that the substitution of Yb decreased the critical temperature (Tc zero), critical current density (Jc) and volume fraction of Bi-2223 phase. The samples have Tc zero in the range 77 to 100 K. Tc zero gradually decreased with an increase in Yb concentration, corresponding to small change of the carrier concentration. Jc was measured to be 5.7512 A/cm2 for pure sample and decreased to 4.1910 A/cm2 for x = 0.025 at 77 K. The crystallographic structure was found to change slightly from tetragonal to orthorhombic in Yb substituted samples. The lattice parameter c of Yb samples decreased due to the incorporation of Yb3+ (0.858 Å) with smaller ionic size compare to Ca2+ (0.99 Å). From the SEM observation, the grain connectivity became weak with smaller plate-like grain for x &gt; 0.025 Yb concentration resulting in the decreased of Jc.

The Effect of Eu Substitution onto Ca Site in Bi(Pb)-2223 Superconductor Via Co-precipitation Method

The samples with nominal composition of Bi16Pb0.4Sr2Ca2−xEuxCu3Oy where x=0.000, 0.025, 0.050, 0.100, and 0.200 prepared by co-precipitation method (COP) have been investigated. They were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), electrical and resistivity measurement using the four-probe method. The temperature dependency on electrical resistance showed the superconducting behavior for all the samples. The critical current density (Jc) and superconductivity transition temperature (Tc zero) of Eu substituted were found to be lower than those of the pure sample. Tc zero varied between 100 and 73 K towards Eu concentration with the highest Tc zero in the Eu substitution was found at 98 K for x=0.025 and decreased gradually for further substitution of Eu corresponding to a small change in the carrier concentration. Jc decreased with increasing Eu substitution, and it was measured to be at 5.7512 A/cm2 in the Eu free sample and at 2.1223 A/cm2 for the x=0.025 sample at 77 K. XRD analyses showed the decrease of the volume fraction of Bi-2223/Bi-2212 (%) which were estimated from 78.13/21.87 for x=0.000 to 23.18/76.82 for x=0.200. The crystallographic structure was found to change slightly from tetragonal to orthorhombic in Eu substituted samples. The lattice parameter c of the Eu samples decreased due to the incorporation of Eu3+ (0.95 A) with smaller ionic size at the Ca2+ (0.99 A) site. From the SEM investigation, the grain connectivity became weak and the porosity increased with the increment of Eu concentration, resulting in the decrease of Jc.

Superconducting Properties of Ag and Sb Substitution on Low-Density YBa2Cu3O δ Superconductor

The effects of silver (Ag) and antimony (Sb) substitution on low-density YBa2Cu3O δ (YBCO) superconductor were investigated. Two series of sample with a nominal composition of YBa2−x Ag x Cu3O δ and YBa2−x Sb x Cu3O δ where x=0.05, 0.10, 0.15, 0.20, 0.30, 0.40 and 0.50 were synthesized and characterized. All Ag-doped samples showed metallic behavior at the normal state and T C onset was found at 90 K. T C zero decreased as the Ag concentration increased. Optimum Ag concentration was achieved at x=0.20 where T C zero has the highest value of 87 K and J C at 70 K is 16.50 A/cm2. For Sb-doped case with x≤0.30, the samples showed metallic behavior above T C onset while semiconducting behavior was shown for x≥0.40. The optimum Sb concentration was achieved at x=0.15 where T C zero is 85 K and J C value measured at 70 K is 2.75 A/cm2. T C onset and T C zero were found to decrease toward higher Sb concentration. The crystallographic structure transformed to tetragonal in Sb-doped samples of x≥0.30 while other samples remain orthorhombic.

Influence of Na, Mg and Yb Substitution for Ca in Bi(Pb)-2223 Superconductor

The effect of Ca substitution by Na, Mg and Yb on the structural and transport properties of Bi1.6Pb0.4Sr2Ca2-xMxCu3Oy (M = Na, Mg and Yb) (x = 0.0 and 0.2) superconducting samples have been investigated. The samples were prepared by the coprecipitation (COP) method. The samples were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), electrical resistivity measurement and critical current density. The critical current density (Jc) and transition temperature (Tc zero) of Na, Mg and Yb substituted with x = 0.2 were found to be lower than the pure sample. Tc zero varies between 100 K and 63 K. Mg concentration was found to give the highest Tc zero of 93 K. Tc zero gradually decreased from Mg, Yb to Na corresponding to a small change in the carrier concentration. Jc decreased with Mg, Yb and Na substitution, and it was measured to be 7.4611 A/cm2, 0.0667 A/cm2, 1.4579 A/cm2 and 1.2479 A/cm2 for pure, Na, Mg and Yb substitution, respectively at 60 K. XRD analysis showed that the decrease of the volume fraction for the 2223 phase and increase of the volume fraction for the 2212 phase with substitution of Na, Mg and Yb. The proportion of Bi-2223/Bi-2212 (%) was estimated from 78.13/21.87 for pure to 51.71/48.29 for Na substitution.

Superconducting Properties of Calcium Substitution in Barium Site of Porous YBa&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt; Ceramics

The influence of calcium substitution at the barium site of porous Y(Ba1-xCax)2Cu3Oδ (x= 0.00, 0.10, 0.20 and 0.30) samples prepared via solid-state reaction method have been investigated. The structure, morphology, critical temperature and critical current were determined by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and four-point probe method, respectively. Generally, the curves of normalized resistance for all samples displayed normal metallic behavior above Tc onset. The Tc zero was between 84 K and 71 K with increase in Ca concentration corresponding to a small change of carrier concentration. The critical current density, Jc decreases with increase in Ca concentration. The highest Jc of 2.657 A/cm2 at 50 K was obtained in Ca-free porous YBCO which is higher than that of Ca-free non porous YBCO. Further substitution of Ca at Ba site decreased Jc monotonously. The increase of Ca concentration decreased the volume of unit cell but the crystallographic structure remains in the orthorhombic form where a≠b≠c. The grains are highly compacted and randomly distributed while the grain size decreased as the Ca concentration increased.

Effect of Ge substitution on excess conductivity and infrared absorption of Tl0·85Cr0·15Sr1−xGexCaCu2O7 superconducting ceramics

Samples of Tl0·85Cr0·15Sr2−xGexCaCu2O7−δ (x = 0–0·3) were successfully synthesised using the solid state synthesis method. Electrical resistance measurements showed that the zero critical temperature value Tc zero was in the range of 90–98 K for x = 0–0·15 and in the range of 60–78 K for x = 0·2–0·3. Analysis of excess conductivity behaviour based on the Aslamazov–Larkin model for the unsubstituted x = 0 compound revealed a two-dimensional fluctuation behaviour. Substitution of Ge in Tl0·85Cr0·15(Sr2−xGex)CaCu2O7−δ induced two- to three-dimensional transition with the highest transition temperature T2D–3D observed at x = 0·10. In this study, the calculation using the Lawrence–Doniach model showed that the sample with the lowest anisotropy was x = 0·08. Fourier transform infrared absorption together with X-ray diffraction data analyses indicate increasing CuO interplane coupling with Ge substitution, which is suggested to cause sustenance of the high Tc zero and metallic normal state behaviour for x = 0–0·15.

Superconductivity and enhancement of critical current density of Ta-substituted TlSr1212 with addition of nanosize MgO

In this paper, the authors report the effect of nanosize MgO particles addition on superconducting and transport critical current density Jc of TlSr1212 superconductors prepared from Tl0·9Bi0·1Sr1·95Ta0·05Ca0·9Y0·1Cu2O7 starting composition using conventional solid state synthesis. X-ray diffraction analyses of Tl0·9Bi0·1Sr1·95Ta0·05Ca0·9Y0·1Cu2O7+xMgO (x=0 to 0·8 wt-%) showed formation of dominant 1212 phase (>90 vol.-%) together with minor 1201 phases. Undoped TlSr1212(x=0) was observed to superconduct with a zero-resistance critical temperature Tc zero of 65 K. The x=0·2 sample recorded the highest Tc zero (80 K) but for higher x, Tc zero was gradually suppressed. The effect of the MgO addition also caused Jc enhancement in zero field with highest value at x=0·2. Using the self-field approximation model, the variation of Jc with temperature for x=0 to 0·4 samples indicate that MgO addition reduces the characteristics length Lc associated with the pinning force. Jc measurements in external magnetic field of 0–0·8 T showed smallest drop in Jc at x=0·2. The Jc enhancements in self-field and in the external fields are suggested to be due to increased flux pinning of the samples as a result of the MgO addition.

Effects of Cu substitution on superconductivity and excess conductivity of Tl1–xCuxSr1·8Yb0·2CaCu2O7–δ (x=0–0·6) ceramics

TlSr1212 samples were synthesised from Tl1–xCuxSr1·8Yb0·2CaCu2O7–δ (x=0·0 to 0·6) starting composition using the solid state synthesis method. Temperature dependent electrical resistance measurements showed gradual change of normal state resistance behaviour from metallic (x=0·0 to 0·3) to semimetallic (x=0·4) and to semiconductor-like behaviour (x=0·5 to 0·6). The best superconducting behaviour for the series was observed at x=0·4 with zero resistance critical temperature Tc zero of 77·6 K. The effects of Cu substitution on superconducting properties are discussed in terms of the concept of average Cu valence. In addition, excess conductivity behaviour was analysed using Asmalazov–Larkin theory to study the effect of Cu substitution on superconductivity fluctuation behaviour. The analysis showed characteristic cross-over from two-dimensional to three-dimensional behaviour with decreasing temperature.

Synthesis of high purity Tl1212 superconductor with ultrafine grains from coprecipitated Tl-free precursor route

In this study, high purity and fine-grained Tl1212 superconductor samples were successfully synthesized from Tl0.8Bi0.2Sr2Ca0.8Y0.2Cu2O7 starting composition by a two-step solid-state reaction method using Tl-free precursor powder prepared from coprecipitation method. XRD pattern of the sample, which was sintered at 1,000 °C for 6 min essentially showed formation of high purity 1212 phase. The sample’s zero resistance critical temperature, T c zero was 91 K and bulk critical current density, J c measured at 40 K in zero magnetic field was 11.2 A/cm2. SEM investigation on the sample revealed ultrafine homogeneous grains that are randomly orientated with grain sizes of approximately 0.5–1 μm. Resintering the sample did not affect its superconducting properties but induced clustering of grains as observed by SEM. It is suggested that the sample be used in specialized measurement techniques such as in ultrasonic studies where high purity and ultrafine-grained samples are required.

Effects of Ag Addition on Superconductivity and Microstructure of DyBa&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7-δ&lt;/sub&gt;-Ag Composite

This paper reports on the effects of Ag addition on physical properties of high temperature superconductors DyBa2Cu3O7-δ (Dy123). A series of the Dy123 - Agx composite was prepared by solid state reaction method with varying amount of metallic silver (x = 0 – 0.3). Resistance versus temperature measurement was done using the four-point-probe method in the temperature range of 79 K to 300 K. Pure DyBa2Cu3O7-δ was found to superconduct with Tc onset of 91 K and Tc zero of 78 K. Addition of Ag at x = 0.05 caused both Tc onset and Tc zero to increase to 93 K and 84 K, respectively. However, Tc onset and Tc zero dropped for higher silver contents. We found that the optimum silver content in DyBa2Cu3O7-δ for best superconducting behavior and hardness is between x = 0.05 and 0.10. Microstructure analysis using SEM and EDAX showed that most of the silver is uniformly distributed along the grain boundaries filling the pores and hence increasing the hardness of the samples.

Superconductivity in ruthenium-based layered cuprate RuSr2(Gd2−xCex)Cu2Oz

We report the preparation procedure of RuSr2(Gd2−xCex)Cu2Oz (Ru-l222) cuprate superconductors from x = 0.5 to 0.7 using the solid state reaction method. All compositions showed an almost single Ru-l222 phase with tetragonal symmetry in the 14/mmm space group and semiconducting or semi-metallic normal state behaviour. The RuSr2(Gd1.4Ce0.6)Cu2Oz material exhibits the highest transition temperature with Tc onset near 48 K and Tc zero at 30 K. The transition temperature is very much dependent on the preparation procedure and can be further improved by optimizing the doping levels.