Ceramic Bi Research Articles

Investigating structural, dielectric, and electrical characteristics of sol–gel synthesized perovskite ceramic Bi0.7Ba0.3(FeTi)0.5O3

The goal of this research is to create a perovskite ceramic with electrical and dielectric properties appropriate for energy storage, medical uses, and electronic devices. A bismuth ferric titanate, Bi0.7Ba0.3(FeTi)0.5O3, doped with barium and crystalline, was effectively synthesized at the A-site via sol–gel synthesis. A rhombohedral structure emerged in the R3́C space group, which was confirmed by room-temperature X-ray studies. An average grain size of 263 nm and a homogeneous grain distribution and chemical composition were confirmed by the results of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The study established a clear relationship between temperature, frequency, and the electrical properties of the material. Impedance spectroscopy and electrical modulus measurements, performed in the frequency range of 1 kHz to 1 MHz and at temperatures ranging from 200 K to 360 K, demonstrated a non-Debye type of relaxation. Furthermore, once the material was produced at various temperatures, its frequency-dependent electrical conductivity was examined using Jonscher’s law. The results demonstrate that barium doping significantly improves the electrical conductivity and dielectric properties compared to pure BiFeTiO₃. Over the complete temperature range, consistent conduction and relaxation mechanisms were discovered. These findings suggest that the chemical may find widespread applicability across a broad temperature range, including electrical fields and capacitors.Graphical

Crystal Structural Characteristics and Electrical Properties of Novel Sol-Gel Synthesis of Ceramic Bi0.75Ba0.25(FeMn)0.5O3.

In this investigation, our primary objective is to explore the structural, morphological, and electrical characteristics of Bi0.75Ba0.25(FeMn)0.5O3 ceramic material synthesized by the sol-gel method. The prepared sample underwent synthesis through the conventional sol-gel technique. Examination through X-ray diffraction (XRD) unveiled a well-defined rhombohedral structure within the R3´C space group. Moreover, to evaluate the purity and nano-grain morphology, we utilized energy dispersive spectroscopy (EDX) and scanning electron microscopy (SEM). Electrical assessments were carried out over a frequency span of 100 Hz to 1 MHz and temperatures ranging from 200 to 340 K. Employing the correlated barrier hopping (CBH) model, we analyzed the AC conductivity of our specimen. The activation energy, determined from both DC conductivity and impedance spectra, demonstrated close correspondence, suggesting that both conductivity and r laxation processes are influenced by similar factors. Notably, the dielectric properties hold significant importance, potentially rendering our sample suitable for electronic applications. Furthermore, we calculated thermodynamic parameters, such as enthalpy (ΔH), entropy change (ΔS), and free energy of activation (ΔF), offering deeper insights into the material's behavior and conductivity mechanisms.

Synergism effect of Pb doping and microstructure optimization on the superconducting properties of Bi-2212 ceramics

Synergism effect of Pb doping and microstructure optimization on the superconducting properties of Bi-2212 ceramics

Distinctive Effects between Hydrothermal and Ultrasound Synthesized SnO2 Nanoparticles on Ceramic Bi1.6Pb0.4Sr2Ca2Cu3O10+δ Superconductor

The effect of additions of two series of SnO2 nanoparticles synthesized using two different methods on crystal structure and superconductivity of Bi1.6Pb0.4Sr2Ca2Cu3O10+δ (BPSCCO) superconductors was investigated. Two series of spherical SnO2 nanoparticles were synthesized independently by using ultra-sonication (US-SnO2) and hydrothermal (HT-SnO2) methods. Polycrystalline samples of (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1−x(SnO2)x, where x ranged between 0, 0.002 and 0.004, were fabricated by the solid-state reaction method. X-ray diffraction patterns showed a decrease in the volume fraction of the Bi-2223 and an increase in that of the Bi-2212 phases. Scanning electron microscopy images presented the “needle-like blossom” on the surface of the US-SnO2 doped samples, while the phenomenon was not found on the HT-SnO2 doped samples. The Tc was decreased extremely with US-SnO2 doping while slightly HT-SnO2 nanoparticle-doped samples. The field dependence of Jc, Jc(B), showed the opposite tendencies on two series of samples: Jc(B) was enhanced on the HT-SnO2 nanoparticle-doped samples, and that was decreased on UT-SnO2 nanoparticle-doped samples. The application of the Dew-Hughes model to explore the flux pinning mechanism exhibited that the point-like pinning centers were dominant on the HT-SnO2 doped samples. On US-SnO2 doped samples, however, the additional pinning center type was not found and could be explained by the observed over-sized SnO2 nano-needle.
 
 

An insight into microstructure and structure stability of Ni-doped Bi2212 ceramics

A series of Bi2Sr2-xNixCaCu2O8+δ (x = 0.00, 0.10, 0.20 and 0.30) ceramics samples were synthesized by Pechini sol-gel method. In this work, the microstructure and structure stability of Ni-doped Bi2212 system were investigated particularly by X-ray diffraction, electron microscopy and high-pressure Raman spectroscopy. It is confirmed that the main phase of all samples is the typical Bi2212 tetragonal phase with space group I4/mmm. As Ni-doping amount x ≤ 0.20, the number of Ni atoms entering the Bi2212 lattice increases gradually with increasing x. These Ni atoms preferentially occupy Sr-sites, resulting in a gradual increase in the a and c axis lengths of Bi2212 structure. The formation of containing-Ni Bi2212 lattice is mainly derived from the insertion of sufficient Ni–O two-dimensional (2D) monomers. Contrarily, when x > 0.20, these Ni–O 2D monomers will preferentially form the NiO particle and the chance of Ni atoms entering the Bi2212 lattice is reduced, which leads to a shrinkage of Bi2212 lattice parameters. Besides, under high-pressure (0–20 GPa) condition, Raman spectrum analysis shows that the OSr peak significantly shifts to the higher wavenumber and Bi2212 phase could still maintain the tetragonal structure, suggesting that it has a relatively high structure stability.

Structure, Microstructure, and Dielectric Properties of Bi<sub>0.5</sub>(Na<sub>0.78</sub>K<sub>0.22</sub>)<sub>0.5</sub>TiO<sub>3 </sub>Lead-Free Ceramic

In this article, the structural, microstructural, and dielectric properties of Lead- free perovskite ceramic Bi0.5(Na0.78K0.22)0.5TiO3 [BNKT] have been reported. The material was synthesized through the solid-state reaction method. The compound formed is found to have a hexagonal structure, confirmed by XRD analysis of the sample. The microstructural analysis of the compound revealed the polycrystalline nature of the ceramic having quasi-cubic grain morphology with distinct grain boundaries. From the dielectric study, it was found that the dielectric constant increases with temperature and attained maximum value at temperature Tc = 335° C, after which it decreased. The frequency independence of transition temperature (Tc) suggested the classic ferroelectric behaviour of the compound. The broad dielectric peak around transition temperature confirms the relaxor behaviour of the compound as well as diffused phase transition at Tc. The value of the relative permittivity and loss tangent at ambient temperature for 1kHz frequency is 627 and 0.223 respectively. The synthesized material can be utilized for the fabrication of capacitors and energy storage applications.

Effect of postannealing processes on the properties of hot-pressed Bi2Sr2Ca1Cu1.75Na0.25Oy (Bi-2212) ceramics

Effect of postannealing processes on the properties of hot-pressed Bi2Sr2Ca1Cu1.75Na0.25Oy (Bi-2212) ceramics

Thermochemical Investigations of Bismuth, Dysprosium, Samarium, and Niobium Oxide Compounds

Ceramic Bi1.4Dy0.6O3 and Bi3Nb0.2Sm0.8O6.2 samples were prepared by solid-phase synthesis. The compounds have cubic structures (space group Fm3m). Their standard enthalpies of formation were determined by solution calorimetry, and their lattice enthalpies were calculated. The lattice enthalpies of Bi3Nb0.2R0.8O6.2 compounds decrease in magnitude when erbium is replaced by samarium, due to the lanthanide radius increasing from erbium to samarium. The lattice enthalpy of Bi1.4Dy0.6O3 has a greater magnitude than the lattice enthalpy of Bi1.2Gd0.8O3.

Addition Effects of MgO‏ on Structure and Physical Properties in Bi-2212 Ceramics

The effect of magnesium on the microstructural and superconducting characteristics of bulk Bi2Sr2CaCu2MgxOy superconductors with x=0 to 0.05 by solid reaction has been examined in this study. Bi2Sr2CaCu2O8+d is formed as the primary phase, and Bi2Sr2CuO6+d (Bi-2201) is present as the parasitic phase, according to XRD data. In doped samples, the c lattice parameter decreases, indicating that Mg has entered the Bi2Sr2CaCu2O8+d crystallographic unit cell. The grain morphology of the samples containing magnesium has changed significantly, and the lamellar structure typical of high temperature superconductors can be seen in the SEM micrographs. The critical temperatures, Tcoff and Tconset, are raised by the addition of Mg, delimiting the superconductive transition. Tconset's maximum value corresponds to x = 0.05.

Enhanced thermoelectric performance of n-type Bi2Te2.7Se0.3 via a simple liquid-assisted shear exfoliation

• By using a simple approach of liquid-assisted shear exfoliation (LASE) coupled with SPS, highly-oriented bulk ceramics of Bi 2 Te 2.7 Se 0.3 with effectively reduced grain size were obtained. • A peak ZT value of 0.83 at 448 K was obtained in-plane due to a synergy of enhanced power factor and suppressed lattice and bipolar thermal conductivities, which is 95% higher that of the pristine sample, demonstrating LASE as a useful assistant process for enhancing the performance of layered thermoelectric materials. A liquid-assisted shear exfoliation (LASE) as a new powder metallurgy method coupled with spark plasma sintering (SPS) was applied for n -type Bi 2 Te 2.7 Se 0.3 and the effects on microstructure and anisotropic transport properties were investigated. Results revealed an effective reduction of average grain size due to LASE and a high texturing in the bulks. Moreover, along the in-plane direction, electrical conductivity was increased noticeably due to an enhanced carrier concentration, leading to a significantly improved power factor of 25 μW cm –1 K –2 at 303 K. Meanwhile, the total thermal conductivity was reduced effectively owing to reduction both in lattice component due to enhanced phonon scattering with the grain size reduction, and in the bipolar component inhibited by the increased carrier concentration. Ultimately, a peak thermoelectric figure of merit (ZT) value of 0.83 was obtained at 448 K along the in-plane direction, increased by 95% compared with the pristine one. These results demonstrate the LASE process as a useful assistant method for enhancing the TE performance of layered materials.

Role of active slip systems induced with holmium impurity in Bi-2212 ceramics on mechanical design performance and morphological properties

Effect of Ho/Bi partial replacement in Bi2.1-xHoxSr2.0Ca1.1Cu2.0Oy (Bi-2212) superconductors on the fundamental structural, morphological and mechanical performance properties are investigated by Scanning Electron Microscopy (SEM) and Vickers hardness (Hv) measurement techniques. Crystallinity quality and surface morphology including the microcrystal coalescence orientations, grain alignment distributions, microscopic structural problems, microvoids, internal defects, uniform surface view, porosity and particle growth distribution are visually examined with the aid of SEM. Basic mechanical performance and characteristic features of Bi/Ho substituted Bi-2212 superconducting ceramics (0.00 ≤ x ≤ 0.10) are also determined with Vickers tests conducted at various loads intervals 0.245–2.940 N. Experimental findings show that the characteristic features enhance seriously in case of x = 0.01 due to refinement of crystallinity quality and slip systems. Thus, the optimum Ho concentration presents the highest mechanical fracture strength to the load applied as a result of better uniform surface appearance and grain orientations, well-connected flaky layers, larger particle size distribution and denser structure, confirmed by the SEM investigations. Namely, much more load is required to accelerate the dislocation movement and crack propagation to the terminal velocity for critical size growth. The fracture predominantly takes place in the transcrystalline regions and hence the propagations are easily controlled with the optimum Ho dopant ions. On the other hand, the increase in the Ho ions in Bi-2212 structure induces the crack-initiating defects for new stress concentration sites. In conclusion, the permanent and non-recoverable deformations appear at even lower indentation test loads. All samples present indentation size effect feature depending on the dominant character of elastic recovery mechanism. Further, original hardness parameters are semi-empirically analyzed in the plateau limit regions using mechanical modelling approaches for the first time. Based on the analyses, Hays–Kendall model exhibits the closest results to the experimental findings.

Effects of different dwell-times under low pelletization pressure on the physical properties of the Bi-2212 ceramics

Effects of different dwell-times under low pelletization pressure on the physical properties of the Bi-2212 ceramics

Effect of co substitution of (Y, Mn) on electrical properties of bismuth ferrite

Using the method of solid-state reaction technique, (Y, Mn) modified Bismuth ferrite ferroelectric ceramic Bi0.8Y0.2(Fe0.5Mn0.5)O3 is prepared. The room temperature XRD analysis confirms the formation of a new single-phase compound with an orthorhombic crystal structure. The electrical properties are analyzed by the impedance analyzer. Through analysis, the dielectric behavior of the compound is explored in broad temperature and frequency span, which shows the strong temperature & frequency dependence characteristics of the compound. The high transition temperature of the parent bismuth ferrite compound (∼830 °C) markedly reduces to 370 °C when Y is substituted at A site and Mn at B site. Temperature-dependent behavior of conductivity and activation energy values estimated in different regimes are calculated from the temperature-dependent ac conductivity graphs, which suggests that the conduction process is of mixed type (i.e. ionic-polaronic and space charge generated from the oxygen ion vacancies). The ac conductivity spectrum obeys Jonscher’s universal power law.

Impedance Spectroscopy Study of Ni-Zn Electrochemical Alkaline Systems with Anode of Nano-sized ZnO Doped with Conducting Ceramics B(Pb)SCCO 2212

For the purpose of electrochemical applications (such as Ni-Zn batteries), we have experimentally studied the electrical impedimetric response of electrochemical systems (ECSs), in which the anodes were fabricated from nano-sized ZnO material doped with high-temperature superconducting ceramics Bi1.7Pb0.3Sr2CaCu2Oy (B(Pb)SCCO 2212) at concentration of either 5, 7, or 10 wt%. The electro-conducting properties of such ECSs with alkaline electrolyte were characterized at ambient temperature by measurements with electrochemical impedance spectroscopy in the frequency range 0.1 Hz –100 kHz. The effect from the ceramics additives on both complex electrical impedance and electrical conductivity of the examined ECSs was estimated.

Role of Active Slip Systems Induced with Holmium Impurity in Bi-2212 Ceramics on Mechanical Design Performance and Morphological Properties

Role of Active Slip Systems Induced with Holmium Impurity in Bi-2212 Ceramics on Mechanical Design Performance and Morphological Properties

Structural, ferroelectric, pyroelectric, and dielectric study of Bi0.5Na0.5TiO3 ceramics synthesized with precursors obtained by the sol–gel method and doped with lanthanum

This study examines the ferroelectric, pyroelectric, and dielectric properties of La-doped bismuth sodium titanate ceramics Bi0.5Na0.51−xLaxTiO3 (BNLT), using amounts of 0–6.7 at. % La. The precursor powders used to make dense BNLT ceramics were obtained via the sol–gel method using the acetic acid route. All samples were calcined at 700 °C for 1 h and sintered at 1150 °C for 30 min in an encapsulated crucible to avoid Na and Bi volatilization yielding relative densities equal to or higher than 94%. The obtained x-ray diffraction patterns, typical of the perovskite structure, confirm the incorporation of lanthanum into the lattice, which evolved from a rhombohedral phase to a mixture of rhombohedral and cubic structures at higher concentrations. The thermogravimetry and differential scanning calorimetry results indicate that the crystallization of precursor powders of BNT takes place between 500 and 700 °C. In addition, the scanning electron microscopy micrographs reveal a decrease in grain size from 4.5 to 0.5 µm with increasing La content. The ferroelectric hysteresis curves show that the best ferroelectric properties were obtained for BNT 1.3% La, where the obtained values of remnant polarization and coercive field were Pr = 29 µC/cm2 and Ec = 39 kV/cm, respectively. At this concentration, the pyroelectric response shows a higher value, four times higher than the pyroelectric signal of pure BNT.

Large Jc Enhancement of Bi-2212 Ceramics by Triple Doping of Li, K, and Na in Bi1.8-x(Li,Na,K)xSr2Ca1.1Cu2.1Oy (x = 0.05, 0.1, and 0.25) Composition

The samples with compositions of Bi1.8-x(Li,Na,K)xSr2Ca1.1Cu2.1Oy (x = 0.05, 0.1, 0.25) were prepared by the solid-state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and DC magnetization measurements. XRD data indicates that all samples have an ideal ratio of Bi-2212 phase; moreover, some impurity phases such as Bi2CaO4 and Bi4Sr4CaCu3O4 are observed to disappear in the maximum alkaline-doped sample (x = 0.25). SEM observations have shown that, with the increase in the amount of alkaline-doped elements, the grain sizes grow significantly. The highest onset superconducting transition temperature obtained from M-T data belongs to the alkaline-doped (Na, K, and Li) samples at high contents (x > 0.05). It has been found that the sample with x = 0.25 (Na, K, Li) has the largest magnetic hysteresis loop, indicating that high level of triple alkaline element doping positively affects the superconductivity properties of the Bi-2212 phase due to the better intergranular coupling. In addition, Bean’s critical model has been used for determining the critical current density. It has been found that maximum Jc of 141.42 × 104 A/cm2 at H = 1 kOe and T = 15 K is achieved in the x = 0.25 alkaline-doped sample, which is higher than the pure samples obtained by the same initial conditions in literature.

Enhanced critical current density in the nano-sized metallic Au-added Bi1.8Sr2Au0.3Ca1.1Cu2.1Oy (Bi-2212) ceramics by means of optimization of the dwell time at 870 °C

This study investigates how the postannealing process applied to Bi1.8Sr2Au0.3Ca1.1Cu2.1Oy (Bi-2212) ceramics at 870 °C can improve their Jc values. Bi1.8Sr2Au0.3Ca1.1Cu2.1Oy has been selected in the present work as initial composition because nano-sized metallic Au additions at large scale positively affect the superconducting properties of Bi-2212 ceramics due to the enhancement of intergranular coupling between the grains, as reported in the literature. These Bi-2212 ceramics were prepared by the solid-state reaction method, including a heat treatment at 860 °C for 96 h for sintering. Then, the samples in the postannealing stage are exposed at different dwell times (8 h, 16 h, and 32 h) at 870 °C. XRD analysis showed that all the samples have similar chemical composition, with Bi-2212 phase as the major one, and the presence of minor impurity phases such as Au, Bi2CaO4 and Bi4Sr4CaCu3O4. The crystalline size of the samples calculated according to the Debye–Scherrer equation increases with increasing dwell time. Magnetization–temperature (M–T) curves were used to determine the superconducting transition temperatures (Tcmag) of all the samples, showing that they are around 70 K. This means that the dwell-time process applied at 870 °C in the present study does not degrade their transition temperatures. To observe how both diamagnetic character and grain growth of the Bi-2212 phases affect magnetic properties, as a function of the different dwell times at 870 °C, magnetic–hysteresis measurements (M–H) at 15 K were performed. It has been found that the thermal treatment at 870 °C for 32 h favors the formation of the widest hysteresis loop due to better intergrain coupling between grains. Finally, the magnetic critical current density (Jcmag) has been obtained through the data from M–H loops according to the critical Bean model. The highest Jc value, 39.92 × 104 A/cm2 under 0.2 T at 15 K, is higher than the Jc of for the samples with the same composition reported in the literature (13.42 × 104 A/cm2 under 0.15 T at 10 K). These results clearly show that appropriate postannealing processes can significantly improve superconducting properties of Bi-2212 ceramics.

A novel research on the subject of the load-independent microhardness performances of Sr/Ti partial displacement in Bi-2212 ceramics

This work is interested in the critical changes in the load-independent microhardness performance parameters with the partial substitution of Sr2+ inclusions for the Ti4+ impurities in the Bi-2212 inorganic solids with the help of the theoretical approximations as regards Meyer’s law (ML), proportional sample resistance (PSR), modified proportional sample resistance (MPSR), elastic/plastic deformation (EPD), Hays–Kendall (HK) and indentation-induced cracking (IIC) models found on the experimental microhardness tests applied to a variety of test loads between 0.245 and 2.940 N for the first time. Moreover, Ti-substituted Bi-2212 bulk ceramics (Bi2.1Sr2.0−xTixCa1.1Cu2.0Oy) are prepared within mole-to-mole ratios of x = 0.000, 0.010, 0.030, 0.050, 0.070, 0.100 by the standard solid-state reaction method in the atmospheric pressure conditions. It is provided that Ti partial substitution in the superconducting system descends unsmilingly the mechanical durability, stability, strength, toughness, critical stress, stiffness and flexural strengths of Bi-2212 superconducting solids studied owing to the increment of crystal structural problems. Moreover, it is obtained that the degradation in the crystal structural leads to diminish the typical ISE characteristic of Bi-2212 superconducting ceramic compounds. At the same time, the results show that all the models (especially IIC approach) can serve as the suitable descriptors for the determination of the variation in the load-independent mechanical performances of the Bi-2212 superconducting materials.

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.