Bi Pb Research Articles

Evaluation of the Radiation-Protective Properties of Bi (Pb)-Sr-Ca-Cu-O Ceramic Prepared at Different Temperatures with Silver Inclusion.

The influences of the sintering process and AgNO3 addition on the phase formation and radiation shielding characteristics of Bi1.6Pb0.4Sr2Ca2Cu3O10 were studied. Three ceramics (code: C0, C1, and C2) were prepared as follows: C0 was obtained after calcination and only one sintering step, C1 was obtained after calcination and two sintering cycles, and C2 was prepared after the addition of AgNO3 at the beginning of the final sintering stage. C2 displayed the maximum volume fraction of the Bi-2223 phase (76.4 vol%), the greatest crystallite size, and high density. The linear mass attenuation coefficient (µ) has been simulated using the Monte Carlo simulation. The µ values are high at 15 keV (257.2 cm−1 for C0, 417.57 cm−1 for C1, and 421.16 cm−1 for C2), and these values dropped and became 72.58, 117.83 and 133.19 cm−1 at 30 keV. The µ value for the ceramics after sintering is much higher than the ceramic before sintering. In addition, the µ value for C2 is higher than that of C1, suggesting that the AgNO3 improves the radiation attenuation performance for the fabricated ceramics. It was demonstrated that the sintering and AgNO3 addition have a considerable influence on the ceramic thickness required to attenuate the radiation.

Critical Current Density and Meissner Effect of Smart Meta-Superconductor MgB2 and Bi(Pb)SrCaCuO.

The smart meta-superconductor MgB2 and Bi(Pb)SrCaCuO increase the superconducting transition temperature (TC), but the changes in the transport critical current density (JC) and Meissner effect are still unknown. Here, we investigated the JC and Meissner effect of smart meta-superconductor MgB2 and Bi(Pb)SrCaCuO. The use of the standard four-probe method shows that Y2O3:Eu3+ and Y2O3:Eu3++Ag inhomogeneous phase significantly increase the JC, and JC decreases to a minimum value at a higher temperature. The Meissner effect was measured by direct current magnetization. The doping of Y2O3:Eu3+ and Y2O3:Eu3++Ag luminescent inhomogeneous phase causes a Meissner effect of MgB2 and Bi(Pb)SrCaCuO at a higher temperature, while the non-luminescent dopant reduces the temperature at which samples have Meissner effect. The introduction of luminescent inhomogeneous phase in conventional MgB2 and copper oxide high-temperature Bi(Pb)SrCaCuO superconductor increases the TC and JC, and Meissner effect is exerted at higher temperature. Therefore, smart meta-superconductivity is suitable for conventional and copper oxide high-temperature superconductors.

Structural and superconducting properties of low-temperature ultrathin PbBi<sub>3</sub> films

Bismuth (Bi), as a stable heaviest element in the periodic table of elements, has strong spin-orbit coupling, which has attracted a lot of attention as the parent material of various known topological insulators. Previous calculations predicted that Bi(111) with a thickness less than eight bilayers and the ultrathin black-phosphorus-like Bi(110) films are single-element two-dimensional (2D) topological insulators. However, it is generally believed that these crystalline bismuth phases are not superconducting or their transition temperature should be lower than 0.5 mK. Lead (Pb) is a good superconducting elementary material, and there is a relatively small difference in radius between the Bi atom and Pb atom. According to the Hume-Rothery rule, it is expected that Pb/Bi alloys in an arbitrary ratio should be superconducting. One may thus expect to form crystalline Bi based superconductors by Pb substitution, which might host intriguing topological superconductivity. While our previous work has demonstrated a low-temperature stable Pb<sub>1–<i>x</i></sub>Bi<sub><i>x</i></sub> (<i>x</i>~0.1) alloy phase in which Pb in the Pb(111) structure is partially replaced by Bi, the Bi crystalline structure-based phases of the superconducting alloys still lack in-depth research. Here, we report a new low-temperature phase of Pb-Bi alloy thin film, namely PbBi<sub>3</sub>, on the Si(111)-(7 × 7) substrate, by co-depositing Pb and Bi at a low temperature of about 100 K followed by an annealing treatment of 200 K for 2 h. Using low-temperature scanning tunneling microscopy and spectroscopy (STM/STS), we characterize <i>in situ</i> the surface structure and superconducting properties of the Pb-Bi alloy film with a nominal thickness of about 4.8 nm. Two spatially separated phases with quasi-tetragonal structure are observed in the surface of the Pb-Bi alloy film, which can be identified as the pure Bi(110) phase and the PbBi<sub>3</sub> phase, respectively, based on their distinct atomic structures, step heights and STS spectra. The PbBi<sub>3</sub> film has a base structure similar to Bi(110), where about 25% of the Bi atoms are replaced by Pb, and the surface shows a <inline-formula><tex-math id="M2">\begin{document}$\sqrt 2 \times \sqrt 2 R{45^ \circ }$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M2.png"/></alternatives></inline-formula> reconstructed structure. The superconducting behavior of the PbBi<sub>3</sub> phase is characterized using variable-temperature STS spectra. We obtain that the superconducting transition temperature of PbBi<sub>3</sub> is about 6.13 K, and the <inline-formula><tex-math id="M3">\begin{document}$2\varDelta (0)/{k_{\text{B}}}{T_{\text{c}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M3.png"/></alternatives></inline-formula> ratio is about 4.62 using the fitting parameter of <inline-formula><tex-math id="M4">\begin{document}$\varDelta (0) = 1.22{\text{ meV}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220050_M4.png"/></alternatives></inline-formula> at 0 K. By measuring the magnetic field dependent superconducting coherence length, the critical field is estimated at larger than 0.92 T. We further investigate the superconducting proximity effect in the normal metal-superconductor (N-S) heterojunction consisting of the non-superconducting Bi(110) domain and the superconducting PbBi<sub>3</sub> domain. The N-S heterojunctions with both in-plane configuration and step-like configuration are measured, which suggest that the atomic connection and the area of the quasi-2D Josephson junctions and the external magnetic field can affect the lateral superconducting penetration length. We also observe the zero-bias conductance peaks (ZBCPs) in the superconducting gap of the PbBi<sub>3</sub> surface in some cases at zero magnetic field. By measuring d<i>I</i>/d<i>V</i> spectra at various temperatures and by adopting a superconducting Nb tip, we identify that the ZBCP originates from the superconductor-insulator-superconductor (S-I-S) junction formed between a superconducting tip and the sample. Nevertheless, the Bi(110)-based PbBi<sub>3</sub> phase may provide a possible platform to explore the intriguing topological superconducting behaviors at the vortexes under magnetic fields, or in the vicinity of the potentially topological superconducting Bi(110) islands by considering the proximity effect.

Ore‐forming process of the Haigou gold deposit in the eastern Central Asian Orogenic Belt, NE China: Constrains from EPMA and LA‐ICP‐MS analysis of Au‐bearing pyrite

AbstractThe Haigou lode deposit, containing 40 t of gold at an average grade of 3.5 g/t, is one of the largest deposits in the Jiapigou gold belt located along the eastern segment of the northern margin of the North China Craton. The deposit comprises 15 gold‐bearing quartz veins hosted in a Carboniferous monzonite–monzogranite stock. Although many studies relating the genesis of this deposit have been carried previously, the understanding of ore‐forming process remains controversial. In this study, we combined field geological mapping with petrography, Electron Probe Micro Analysis (EPMA) and in situ LA‐ICP‐MS analysis of gold‐bearing pyrite to provide new insight into the genesis of the gold deposit. Our results show that Au in the Haigou gold deposit mainly exists in the form of native gold. LA‐ICP‐MS in situ multi‐element mapping shows that Au has a significant positive correlation with Ag, Te, Bi and Pb in Au‐bearing pyrite, indicating that these elements co‐precipitated with Au in pyrite lattice. The ore‐forming fluid existed under medium to low temperature, aiding complexing of the gold with sulfur, chlorine, and tellurium. Decoupling of sulfide and telluride complexes facilitated gold precipitation in the Haigou area. The abundance of lead and nickel tellurides in the Haigou gold deposits with general absence of tellurium in native gold is indicative of expulsion of tellurium through boiling during the process of fluid migration and evolution. Also, coexistence of Bi in native gold indicates that they were at Au–Bi eutectic. The gold‐bearing pyrite is characterized by dispersed magnetite in and around the fractures. The Au–Te–Bi–Pb element anomalies indicate that fluid oxygen fugacity increases while sulfur fugacity decreases with time, resulting in Au precipitation. Our results provide a new theoretical basis for the establishment of metallogenic model and deep prospecting of the Haigou gold deposit.

Structural and superconducting properties of low-density Bi(Pb)-2223 superconductor: Effect of Eu2O3 nanoparticles addition

This paper presented the result of the structural analysis of Europium, Eu nanoparticles addition in low-density Bi(Pb)-2223 superconductor. Polycrystalline bulks with nominal composition Bi1.6Pb0.4Sr2Ca2Cu3Oy + xEu2O3 samples where x = 0.0, 0.2, 0.4, 0.6 and 0.8 wt% were prepared via solid-state reaction method. Low-density samples were created by adding crystalline sucrose into mixed powders and burn at 400 °C for two hours. The samples were characterized using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) for structural characterization while resistivity measurement was determined by using four-point probe method. Phase analysis by XRD indicated that both Bi-2212 and Bi-2223 phases coexist within the samples having a tetragonal crystal structure. As Eu concentration increases, the amount of Bi-2223 phase slightly decreased which signifies that Eu nanoparticles favour the growth of Bi-2212 phase. It was observed that the highest Tc and Jc values for the addition sample found at x = 0.2 wt%.

Reinforcing Increase of ΔTc in MgB2 Smart Meta-Superconductors by Adjusting the Concentration of Inhomogeneous Phases.

Incorporating with inhomogeneous phases with high electroluminescence (EL) intensity to prepare smart meta-superconductors (SMSCs) is an effective method for increasing the superconducting transition temperature (Tc) and has been confirmed in both MgB2 and Bi(Pb)SrCaCuO systems. However, the increase of ΔTc (ΔTc = Tc ‒ Tcpure) has been quite small because of the low optimal concentrations of inhomogeneous phases. In this work, three kinds of MgB2 raw materials, namely, aMgB2, bMgB2, and cMgB2, were prepared with particle sizes decreasing in order. Inhomogeneous phases, Y2O3:Eu3+ and Y2O3:Eu3+/Ag, were also prepared and doped into MgB2 to study the influence of doping concentration on the ΔTc of MgB2 with different particle sizes. Results show that reducing the MgB2 particle size increases the optimal doping concentration of inhomogeneous phases, thereby increasing ΔTc. The optimal doping concentrations for aMgB2, bMgB2, and cMgB2 are 0.5%, 0.8%, and 1.2%, respectively. The corresponding ΔTc values are 0.4, 0.9, and 1.2 K, respectively. This work open a new approach to reinforcing increase of ΔTc in MgB2 SMSCs.

Effect of BaCO3 addition on critical temperature of Bi-Pb-Sr-Ca-Cu-O superconductor

Bi-Pb-Sr-Ca-Cu-O high temperature superconductor has been applied in the field of electricity as power transport cables. This work has been carried out to investigate the effect of addition of BaCO3 on Bi1, 6Pb0, 4Sr2Ca2Cu2O10 superconductors. Solid state reaction method was used to prepare all samples. The starting materials were Bi2O3, PbO2, SrCO3, CaCO3, CuO, and BaCO3 powder. Starting materials without BaCO3 were ground using a mortar agate for 3 h. After calcination process of 820°C for 20 h, samples were mixed with BaCO3 (1 %wt, 2 %wt) and then sintered by 850°C for 30 h. Characterizations ware conducted by using cryogenic magnet to determine the critical temperature (Tc), SEM-EDX to analyze morphology, and XRD to determine the phase formed. There were semiconductor properties at high temperature and it was found that the addition of BaCO3 decreased Tc of the samples. 1 %wt BaCO3 showed a critical temperature with Tconset = 86 K and Tczero = 52 K, and 2 %wt of BaCO3 has Tconset of 80 K, and Tczero of 23 K. The surface morphology contains agglomeration and there is a lot of porosity. The dominant phase formed is Bi(Pb)-2212 with a volume fraction of 64.71%.

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content.

A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the critical transition temperature (TC) of B(P)SCCO by electroluminescence (EL) energy injection of inhomogeneous phases. However, the increase amplitude ΔTC () of TC is relatively small. In this study, a smart meta-superconductor B(P)SCCO with different matrix sizes was designed. Three kinds of raw materials with different particle sizes were used, and different series of Y2O3:Sm3+, Y2O3, Y2O3:Eu3+, and Y2O3:Eu3++Ag-doped samples and pure B(P)SCCO were prepared. Results indicated that the TC of the Y2O3 or Y2O3:Sm3+ non-luminescent dopant doping sample is lower than that of pure B(P)SCCO. However, the TC of the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminescent inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With the decrease of the raw material particle size from 30 to 5 μm, the particle size of the B(P)SCCO superconducting matrix in the prepared samples decreases, and the doping content of the Y2O3:Eu3++Ag or Y2O3:Eu3+ increases from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content enhances the ΔTC. When the particle size of raw material is 5 μm, the doping concentration of the luminescent inhomogeneous phase can be increased to 0.4%. At this time, the zero-resistance temperature and onset transition temperature of the Y2O3:Eu3++Ag doped sample are 4 and 6.3 K higher than those of pure B(P)SCCO, respectively.

Transport and magnetic properties of Bi(Pb)2212 superconducting ceramics doped by low rate of potassium

Abstract Samples of Bi1.5Pb0.5(Sr1.8−xKx)CaCu2O8+d and Bi1.5Pb0.5Sr1.8CaCu2O8+dKx have been prepared from powders of carbonates and primary oxides using the solid state reaction method and compared in this study. In the first case, potassium (K) is substituted in the strontium (Sr) site. In the second one, K is added. A part of the paper is devoted to discuss the results obtained by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) observations of (Bi,Pb)2Sr1.8CaCu2O8+d samples doped by potassium to provide additional microstructural information related to the doping method. These analyses are supplemented by resistivity and magnetic measurements. Results show how the rate of doping by potassium affects transport and magnetic properties of Bi(Pb)2212 phase. The critical current density (Jc) is improved using the two methods and it reaches a double value by the addition of K as compared to the undoped sample.

Characterization of structure and superconducting properties of low-temperature phase of Pb-Bi alloy films

Lead-bismuth (Pb-Bi) alloys, as a superconducting material, have been widely studied at their superconducting transition temperatures and the critical magnetic fields for different composition ratios. Most of experimental studies focused on the stable ε phase formed at high temperatures, but less on the Pb-Bi alloys grown at low temperatures. So far, the structural and superconducting properties of the low-temperature Pb-Bi phases are far from good understanding. Here, we report our investigation of structural and superconducting properties of a low-temperature phase of Pb-Bi alloy. The Pb-Bi alloy films with a nominal thickness of about 6 nm are prepared by co-depositing Bi and Pb on Bi(111)/Si(111)-(7 × 7) substrates at a low temperature of 100 K followed by annealing at a treatment of 200 K for 2 h. The structural and superconducting properties of the Pb-Bi alloy films are characterized in situ by using low-temperature scanning tunneling microscopy/spectroscopy (STM/STS). It is observed that the spatially separated phases of nearly pure Bi(111) domains and Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy domains are formed in the films, where these phases can be identified by their distinct differences in the atomic structure and the distributions of step heights in the atomically resolved STM images, as well as by their distinguished STS spectra. The Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy phase presents the structure of Pb(111), in which about <i>x</i> ≈ 0.1 Bi is substituted for Pb. The STS spectra show that the Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy phase is superconducting, with a transition temperature <i>T</i><sub>c</sub> = 7.77 K derived from the variable-temperature measurements. This transition temperature is higher than that in pure Pb film (6.0–6.5 K), which can be well explained by the Mattias rules, with considering the fact that the average number of valance electrons increases after Bi atoms with five valance-electrons have been substituted for Pb atoms with four valance-electrons. The analysis shows that the ratio <inline-formula><tex-math id="M1">\begin{document}$ 2\Delta (0)/{k_{\rm{B}}}{T_{\rm{C}}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M1.png"/></alternatives></inline-formula> is about 4.94 with the superconducting gap <inline-formula><tex-math id="M2">\begin{document}$ \varDelta (0) = 1.66$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="17-20210482_M2.png"/></alternatives></inline-formula> meV at 0 K, indicating that the Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy is a strongly-coupled superconductor. The non-superconducting Bi(111) and the superconducting Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> alloy domains form an in-plane superconductor-normal metal-superconductor (S-N-S) Josephson junction. The proximity effect in the Bi(111) domains is measured at different N-S junctions, which suggests that the lateral superconducting penetration length in Bi(111) might be affected by the area of the quasi-two-dimensional interface. The superconducting gap in the Bi(111) region with a narrow width of 23 nm in an S-N-S Josephson junction is found to be greatly enhanced due to the existence of multiple Andreev reflections. Since Bi can host potential topological properties, the lateral Bi(111)-Pb<sub>1–<i>x</i></sub>Bi<i><sub>x</sub></i> heterostructures, because of the existing proximity effect, could have potential applications in exploring the novel topological and superconducting phenomena.

Behavior of enrichment and migration path of Cu–Ag–Pd–Bi–Pb in the recovery of waste multilayer ceramic capacitors by eutectic capture of copper

Recycling waste multilayer ceramic capacitors (MLCCs) has attracted much attention owing to its rich metal resource and environment pollution. Existing recycling processes have deficiencies in environmental protection, efficiency and metal purity. Capture technology is promising with advantages of efficient enrichment and less pollution, which was applied to recycle metals in this study. In order to study the mechanism for it, the behavior of enrichment and migration of metals in the recovery of waste MLCCs by eutectic capture of copper was discussed. The recovery rates of Ag, Pd and Bi were 87.53%, 100% and 100%, respectively. Alloy (Cu–Ag–Pd–Bi–Pb) and recyclable slag were obtained. There were three phases of Ag, Cu–Pd and Bi–Pb with the analysis of morphology and composition for the alloy. Then the capture mechanism was revealed. The slag and metal separated due to differences in chemical bonds, surface energy, density and viscosity. The interaction of metals was analyzed through phase diagrams and density functional theory. Pd tended to enter Cu phase. Ag and Cu existed as two phases. Bi and Pb neither entered Ag nor Cu phase based on phase diagrams and formation energy. This study provides a theoretical basis for the application of capture technology in metal enrichment.

Low-Temperature Multielement Fusible Alloy-Based Molten Sodium Batteries for Grid-Scale Energy Storage.

The sustainable future of modern society relies on the development of advanced energy systems. Alkali metals, such as Li, Na, and K, are promising to construct high-energy-density batteries to complement the fast-growing implementation of renewable sources. The stripping/deposition of alkali metals is compromised by serious dendrite growth, which can be intrinsically eliminated by using molten alkali metal anodes. Up to now, most of the conventional molten alkali metal-based batteries need to be operated at high temperatures. To decrease the operating temperature, we extended the battery chemistry to multielement alloys, which provide more flexibility for wide selection and rational screening of cost-effective and fusible metallic electrodes. On the basis of an integrated experimental and theoretical study, the depressed melting point and enhanced interfacial compatibility are elucidated. The proof-of-concept molten sodium battery enabled by the Bi–Pb–Sn fusible alloy not only circumvents the use of costly Ga and In elements but also delivers attractive performance at 100 °C, holding great promise for grid-scale energy storage.

Machine Learning F-Doped Bi(Pb)–Sr–Ca–Cu–O Superconducting Transition Temperature

The increase in critical temperature of high-temperature superconductors fulfills needs of practical applications with liquid-helium-free refrigeration and a delay in magnet failure. But the research requires significant manpower for materials synthesis, characterization, and quench detection, as well as costly equipment and facilities. In this study, we develop the Gaussian process regression (GPR) model to shed light on the relationship between process parameters and superconducting transition temperature for BiPbSrCaCuOF superconductors. The modeling approach has a high degree of accuracy and stability, contributing to fast low-cost estimations of superconducting transition temperature.

Fluctuation, Diamagnetic Transition, and FTIR Spectra of La Substituting Ca in (Bi,Pb):2223 Superconductor

We report here fluctuation, diamagnetic transition, and FTIR spectra in Bi1.7Pb0.30 Sr2Ca2-xLaxCu3Oy superconductor with various x values (0.00 < x < 0.30). It is found that the magnetic moment is negative for the samples below the onset of diamagnetism in both field cooling (FC) and zero-field cooling (ZFC). Although the magnetic moments are shifted to lower values close to zero as La increases up to 0.30, they are higher for Fc than for ZFC. Furthermore, the onset temperature of diamagnetic transition (TcM) for La = 0.30 sample is 83 K, which is about 30 K higher than that obtained from resistivity data (TcR = 53 K). On the other hand, the logarithmic plots of excess conductivity ∆σ and reduced temperature e for the samples reveal three different exponents corresponding to two crossover temperatures in the slope of each plot. The first exponent occurs in the normal field region (NFR) and its values are 0.30 (3D), 0.50 (3D), 0.20 (3D), and 2.04 (0D). The second exponent occurs in the mean field region (MFR) and its values are 0.75(2D), 0.44 (3D), 0.65 (2D), and 0.36 (3D). The third exponent occurs in the critical field region (CFR) and its values are 0.51 (3D), 0.99 (2D), 0.38 (3D), and 0.65 (2D). Interestingly, the Ginzburg-Landau parameter, critical magnetic fields, and critical current density are gradually increased as La increases up to 0.30, while the interlayer coupling, coherence lengths, anisotropy, and Ginzburg number are decreased. Finally, the FTIR absorption spectra of the samples show nine successive peaks due to O-H, Bi(Pb):2223, residual carbon, SrCo, CaCo3 and CuO, and M-O, respectively. These results are discussed in terms of the correlation between hole carriers/Cu ions and excess oxygen which are introduced by La through CuO2 planes of BSCCO superconductors. PACS: 74.25.Bt74.62.Dh74.62.En74.72.gh

Enhanced thermoelectric performance of hot-press Bi-doped n-type polycrystalline PbS

Lead sulfide (PbS) is a type of promising thermoelectric materials which is consist of elements with high natural abundance. However, the relatively low conversion efficiency limits its further application due to the high lattice thermal conductivity of PbS compared with that of PbTe. It has been widely accepted that nanostructuring and doping are effective ways to enhance the thermoelectric properties. Herein, nano/micro structure Bi doped PbS materials have beensynthesized by a facile method of hydrothermal synthesis. The nano/micro structure material systems exist abundant interface which could scatter mid- and low-frequency phonons effectively, combined with point defect such as Bi–Pb scattering high-frequency phonons, and thus the results show that the lattice thermal conductivity of PbS decreases with the increasing concentration of Bi3+ doping as expected. Moreover, the optimal power factor (PF) can be obtained by tuning the carrier concentration and mobility at the same time. The optimal thermoelectric figure of merit (ZT) can reach 0.89 for Pb0.96Bi0.04S at 773K and rises with the increase of the temperature without sign of saturation. Our work may shed light to further possible and environmentally friendly application of PbS-based thermoelectric materials.

Excess Conductivity, Diamagnetic Transition and FTIR Spectra of Ca Substituted by La in (Bi,Pb):2212 Superconducting System

We report here measurements of the excess conductivity, the diamagnetic transition and the FTIR spectra of Bi1.7Pb0.30 Sr2Ca1−xLaxCu2Oy superconductor with various x values (0.00 ≤ x ≤ 0.30). It is found that the magnetic moment is negative below the diamagnetic transition in both field cooling (FC) and zero-field cooling (ZFC) for all samples. Furthermore, the magnetic moment is gradually shifted to lower values close to zero as the La concentration increases up to 0.30, but their values for FC are higher than that of ZFC. Moreover, the onset of diamagnetism (TcM) for the La = 0.30 sample is 80 K, which is about 29 K higher than that obtained from resistivity (TcR= 51 K). On the other hand, the logarithmic plots of excess conductivity ∆σ and reduced temperature Є reveal three different exponents corresponding to two crossover temperatures in the slope of each plot for all samples. The first exponent occurs in the normal field region (NFR) and its values are 0.90 (2D), 0.67 (2D), 0.23 (3D) and 0.77 (2D). The second exponent occurs in the mean field region (MFR) and its values are 0.51(3D), 0.23 (3D), 1.05 (2D) and 0.17 (3D). The third exponent occurs in the critical field region (CFR) and its values are 0.90 (2D), 0.78 (2D), 0.70 (2D) and 0.35 (3D). Interestingly, The Ginzburg-Landau parameter, critical magnetic fields and critical current density are gradually increased with La concentration up to 0.30, while the interlayer coupling, coherence lengths, anisotropy and Ginzburg number are decreased. Finally, the FTIR absorption spectra of the samples show nine successive peaks due to O–H, Bi(Pb):2223, residual carbon, SrCO, CaCO3 and CuO, and M–O, respectively. These results are discussed in terms of the correlation between hole carriers/Cu ions and excess oxygen which are introduced by La through CuO2 planes of BSCCO superconductors.

Smart Metastructure Method for Increasing TC of Bi(Pb)SrCaCuO High-Temperature Superconductors

Improving the critical transition temperature (TC) of Bi(Pb)SrCaCuO (B(P)SCCO) high-temperature superconductors is important; however, considerable challenges exist. In this study, on the basis of the metamaterial structure and the idea that injecting energy will promote the formation of electron pairs, a smart meta-superconductor B(P)SCCO consisting of B(P)SCCO microparticles and Y2O3:Eu3++Ag or Y2O3:Eu3+ luminophore was designed. In the applied electric field, the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminophore generates an electroluminescence (EL), thereby, promoting the TC via EL energy injection. A series of Y2O3:Eu3++Ag or Y2O3:Eu3+ luminous inhomogeneous phase-doped B(P)SCCO samples was prepared. Meanwhile, the B(P)SCCO sample doped with 0.2 wt% Y2O3 or Y2O3:Sm3+ nonluminous inhomogeneous phase was also prepared. Results indicated that the TC of 0.2 wt% Y2O3 or Y2O3:Sm3+ doping sample is lower than that of pure samples. However, the TC of the sample doped with 0.2 wt% Y2O3:Eu3++Ag or Y2O3:Eu3+ luminophore is higher than that of pure sample. This outcome further demonstrated that the smart metastructure method can improve the TC of B(P)SCCO.

Impact of Boron Nitride Additive on the Phase Formation and Transport Properties of Bi(Pb)-2223 Superconductor

Doping of a high-temperature Bi(Pb)-2223 superconductor with various additives, which can act as pinning centers and / or accelerate the formation of a superconducting phase, is an effective tool for obtaining Bi(Pb)-2223 samples with improved characteristics. In this paper, we studied the effect of the addition of hexagonal boron nitride (h-BN) on the phase formation and critical transport current density of ceramic samples Bi(Pb)-2223. Samples with a nominal composition of Bi1.7Pb0.3Sr2Ca2Cu3Oy [BN]x, x = 0–0.25 were prepared by the solid-phase reaction method. Two different doping methods were used: the introduction of hand-ground BN powder at the initial stage of synthesis and the addition of BN powder subjected to high-energy grinding in a ball mill before pelletizing. The phase composition of the obtained samples was studied by X-ray diffraction. The microstructure and elemental composition of the samples were studied using a scanning electron microscope with an X-ray microanalyzer. The resistivity and critical current density were measured using the standard four-probe method. The results show that boron nitride is a suitable additive to increase the rate of formation and critical transport current density Bi(Pb)-2223.

Surface Morphology Studies on Laser Irradiated Target and Bi(Pb)SrCaCuO Thin Films

In this study, pulsed laser deposition technique was used to deposit bismuth plumbum strontium calcium copper oxide {Bi (Pb)SrCaCu0} thin films on MgO single crystal substrate. Solid state procedure which is inexpensive technique used in the production process of the Bi (Pb)SrCaCu0 superconductor bulk sample. In this work, Handy YAG Lasers (model: HYL 101 E) has been used. It is a high power class 4 solid state (ND: YAG) Q-switched pulsed laser and 532 nm (visible green: second harmonic) has been used to ablate the films. The substrate used in this work was single crystal MgO with the (100) orientation. Scanning Electron Microscopy (SEM) was used to observe the microstructure of fracture surface and cross section of thin film materials. Variable Pressure Scanning Electron Microscope (LEO-VPSEM) was used to study the correlation between the microstructure features. SEM studies have shown that the surface morphology of the bulk sample comprises platelets of average size ≈10μm with uniform and homogenous microstructure. The typical morphology of the as deposited films showed a continuous phase, granular structure, which spherical particles up to 5μm in diameter. The most prominent types of particulates BPSCCO films on MgO substrate are droplets with smooth surface, bigger droplets with granular surface, spherically-shaped features confined by randomly oriented facets, submicron rod-like features, Cu-enriched needles, platelets, irregularly-shaped Cu-rich outgrowths, strongly Cu-enriched tabular outgrowths, big target fragments, island growth structure, cubic and rectangular cubic structures. SEM analysis also showed that the deposition time have a pronounced influence on the particle size. The target morphology, which develops under laser-irradiation, depends on the laser fluence and the technique, by which the laser beam is moved relatively to the target during ablation. Laser-irradiated surfaces normally become altered both physically and chemically and morphological changes take the form of periodic structures such as ripples and ridges.

Impact of Eu Nanoparticles Substitution for Ca Site in Bi(Pb)-2223 Cuprates Superconductor

The sample with nominal composition of Bi1.6Pb0.4Sr2Ca2-xEuxCu3Oy where x = 0.000, 0.0025, 0.020, 0.050 and 0.100 were synthesized through solid state reaction method. The effect of Eu2O3 nanoparticles doping on the superconducting and structural properties were studied by means of critical temperature, TC, critical current density, JC, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The amount of 2223 phase gradually decreased with the increment of Eu concentration which indicates that Eu nanoparticles substitution at Ca site favours the growth of 2212 phases. The sample with higher porosity was found to be decreased in critical temperature, TC as well as critical current density, JC due to the lack of effective surface area for current flowing. The best superconducting properties were observed at x = 0.0025 substitutes into Ca site for Bi (Pb)-2223 host sample.