Search Results (14)

With the intensification of the energy crisis, it is urgent to vigorously develop new environment-friendly energy storage materials. In this work, coexisting ferroelectric and relaxor-ferroelectric phases at a nanoscale were constructed in Sr(Zn_1/3Nb_2/3)O₃ (SZN)-modified (Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (BNBT) ceramics, simultaneously contributing to large polarization and breakdown electric field and giving rise to a superior energy storage performance. Herein, a high recoverable energy density (W_rec) of 5.0 J/cm³ with a conversion efficiency of 82% at 370 kV/cm, a practical discharged energy density (W_d) of 1.74 J/cm³ at 230 kV/cm, a large power density (P_D) of 157.84 MW/cm³, and an ultrafast discharge speed (t_0.9) of 40 ns were achieved in the 0.85BNBT-0.15SZN ceramics characterized by the coexistence of a rhombohedral-tetragonal phase (ferroelectric state) and a pseudo-cubic phase (relaxor-ferroelectric state). Furthermore, the 0.85BNBT-0.15SZN ceramics also exhibited excellent temperature stability (25–120 °C) and cycling stability (10⁴ cycles) of their energy storage properties. These results demonstrate the great application potential of 0.85BNBT-0.15SZN ceramics in capacitive pulse energy storage devices. Full article

BaTiO₃-Bi(Zn,Ti)O₃ (BT-BZT) ceramics have been used as capacitors due to their large dielectric permittivity and excellent temperature stability and are good candidates for lead-free materials for electrocaloric and energy storage devices. However, BT-BZT ceramics often suffer from inferior properties and poor reproducibility due to heterogeneous compositional distribution after calcination and sintering. In this work, (1−x)BT-xBZT ceramics (x = 0~0.2) were fabricated with nano-sized BaTiO₃ raw materials (nano-BT) by a solid-state reaction method to enhance the chemical homogeneity. The (1−x)BT-xBZT ceramics prepared from the nano-BT showed larger densities and more uniform microstructures at the lower calcination and sintering temperatures than the samples prepared from more frequently used micrometer-sized raw materials BaCO₃, TiO₂, Bi₂O₃, and ZnO. The (1−x)BT-xBZT ceramic prepared from the nano-BT displayed a phase transition from a tetragonal ferroelectric to a pseudo-cubic relaxor in a narrower composition range than the sample prepared from micro-sized raw materials. Larger adiabatic temperature changes due to the electro-caloric effect (ΔT_ECE) and recoverable energy storage density (U_rec) were observed in the samples prepared from the nano-BT due to the higher breakdown electric fields, the larger densities, and uniform microstructures. The 0.95BT-0.05BZT sample showed the largest ΔTECE of 1.59 K at 80 °C under an electric field of 16 kV/mm. The 0.82BT-0.18BZT sample displayed a U_rec of 1.45 J/cm², which is much larger than the previously reported value of 0.81 J/cm² in BT-BZT ceramics. The nano-BT starting material produced homogeneous BT-BZT ceramics with enhanced ECE and energy storage properties and is expected to manufacture other homogeneous solid solutions of BaTiO₃ and Bi-based perovskite with high performance. Full article

Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO₃-0.1Bi(Mg_2/3Nb_1/3)O₃ (BT-BMN) ceramics with x wt% ZnO-Bi₂O₃-SiO₂ (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm³ with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices. Full article

In the Carajás Mineral Province, gossan formation and lateritization have produced numerous supergene orebodies at the expense of IOCG deposits and host rocks. The Alvo 118 deposit comprises massive and disseminated hypogene copper sulfides associated with gossan and mineralized saprolites. The hypogene reserves are 170 Mt, with 1% Cu and 0.3 ppm Au, while the supergenes are 55 Mt, comprised of 30% gossan and 70% saprolite, with 0.92% Cu and 0.03 ppm Au. The gossan includes goethite, malachite, cuprite, and libethenite zones. The saprolite comprises kaolinite, vermiculite, smectite, and relics of chlorite. In the hypogene mineralization, Ag, Te, Pb, Se, Bi, Au, In, Y, Sn, and U are mainly hosted by chalcopyrite and petzite, altaite, galena, uraninite, stannite, and cassiterite. In the gossan, Ag, Te, Pb, Se, and Bi are hosted by Cu minerals, while Au, In, Y, Sn, and U are associated with iron oxyhydroxides, in addition to Zn, As, Be, Ga, Ga, Mo, Ni, and Sc. As supporting information, δ⁶⁵Cu values indicate that the gossan is immature and, at least partly, not affected by leaching. In the saprolite, Ga, Sc, Sn, V, Mn, Co, and Cr are associated with the iron oxyhydroxides, partially derived from the host rock weathering. The δ⁵⁶Fe values indicate that hypogene low contribution of the hypogene mineralization to the saprolite iron content. The association of Al₂O₃, Hf, Zr, Th, TiO₂, Ce, La, Ba, and Sr represents the geochemical signature of the host rocks, with dominant contributions from chlorites, while In, Y, Te, Pb, Bi, and Se are the main pathfinders of Cu mineralization. Full article

Radiation has become an essential part in medicine and researchers are constituently investigating radiation shielding materials that are suitable for different medical applications. Glass, due to its properties, has been considered an excellent radiation shield for such applications. One of the most common glasses used as a radiation shield is the ZnO-Bi₂O₃-B₂O₃-SiO₂ anti-radiation glass. Heavy metal oxides have many desirable properties such as high density, transparency to visible light, stability in air and water, high interaction cross section, high infrared transparency, and good absorption of radiation, which make them desirable to be used as modifiers with anti-radiation glass. Research has been focusing on environmentally friendly shielding material which leads to non-lead modifiers such as Na₂O, Al₂O₃, MgO, TiO₂, SrO, Sb₂O₃, and BaO, which have become more desired than PbO. So far, ZnO-Bi₂O₃-B₂O₃-SiO₂’s photon shielding properties have been studied experimentally with the addition of BaO at certain energies only. In this work, different heavy metal oxides are added as modifiers to ZnO-Bi₂O₃-B₂O₃-SiO₂ glass in order to investigate theoretically their effects on the shielding properties of the glass at a wide range of photon and neutron energies. Simulation is cost- and time-effective when it comes to investigating different compositions of glass and different modifiers with different weight percentages at any energy range for any type of radiation. Simulation could be considered the first step in order to identify the best mixture with the best weight fractions prior to any experimental investigations of other desired properties based on the needed application. In this work, the photon- and neutron-shielding capabilities of the ZnO-Bi₂O₃-B₂O₃-SiO₂ anti-radiation glass is investigated with different weight fractions of heavy metal oxides at wide photon and neutron energy ranges. Geant4, which is a Monte Carlo-based powerful toolkit, is used to find the mass attenuation coefficients (µm) of photons, as well as the effective removal cross sections (ΣR) of neutrons, of all the investigated samples in the studied energy range. Full article

In order to promote the research of green energy in the situation of increasingly serious environmental pollution, dielectric ceramic energy storage materials, which have the advantages of an extremely fast charge and discharge cycle, high durability, and have a broad use in new energy vehicles and pulse power, are being studied. However, the energy storage density of ordinary dielectric ceramic ferroelectric materials is low, so, in this paper, we have divided eight components based on BaTiO₃ (BT). Through the traditional solid phase sintering method, AB positions were replaced with various elements of different proportions to improve their energy storage density and the energy storage efficiency of BT-based ferroelectric materials. In this paper, we studied the results of XRD, Raman, ferroelectric, dielectric, and impedance tests of doped samples, and the best components were determined. The (1−x)BT−xBi(${\mathrm{M}\mathrm{g}}_{1/3}{\mathrm{Z}\mathrm{n}}_{1/3}{\mathrm{T}\mathrm{a}}_{1/6}{\mathrm{N}\mathrm{b}}_{1/6}$)O₃ series of ceramics are made by the incorporation of five elements, Bi³⁺, Mg²⁺, Zn²⁺, Ta⁵⁺, and Nb⁵⁺. With the rising electric hysteresis loop of the doping amount x thin, the saturation polarization strength and residual polarization strength decrease, and the energy storage density rises first and then decreases. The dielectric characteristic after x = 0.08 showed a flat dielectric peak, indicating that the ferroelectric relaxation had been formed. The energy storage density and efficiency of the best component x = 0.12 reached 1.75 J/cm³ and 75%, respectively, and the Curie temperature was about −20 °C, so it has the potential to be used at room temperature. Full article

Geochemical baselines are crucial to explore mineral resources and monitor environmental changes. This study presents the first Laos geochemical baseline values of 69 elements. The National-scale Geochemical Mapping Project of Lao People’s Democratic Republic conducted comprehensive stream sediment sampling across Laos, yielding 2079 samples collected at 1 sample/100 km², and 69 elements were analyzed. Based on the results of LGB value, R-mode factor analysis, and scatter plot analysis, this paper analyzes the relationship between the 69 elements and the geological background, mineralization, hypergene processes and human activities in the study area. The median values of element contents related to the average crustal values were: As, B, Br, Cs, Hf, Li, N, Pb, Sb, Zr, and SiO₂, >1.3 times; Ba, Be, Cl, Co, Cr, Cu, F, Ga, Mn, Mo, Ni, S, Sc, Sr, Ti, Tl, V, Zn, Eu, Al₂O₃, Tot.Fe₂O_3, MgO, CaO, and Na₂O, <0.7 times; and Ag, Au, Bi, Cd, Ge, Hg, I, In, Nb, P, Rb, Se, Sn, Ta, Th, U, W, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and K₂O, 0.7–1.3 times. R-mode factor analysis based on principal component analysis and varimax rotation showed that they fall into 12 factors related to bedrock, (rare earth, ferrum-group, and major Al₂O₃ and K₂O elements; mineralization–Au, Sb, and As) and farming activities–N, Br, S, and C). This study provides basic geochemical data for many fields, including basic geology, mineral exploration, environmental protection and agricultural production in Laos. Full article

Depolarization behavior is one of the main shortcomings of (Bi_0.5Na_0.5)TiO₃-based ceramics. Considering the undesirable efficiency of traditional modification methods, in this paper a series of 0–3 type ceramic composites 0.85(Bi_0.5Na_0.5)TiO₃-0.11(Bi_0.5K_0.5)TiO₃-0.04BaTiO₃-x mol% ZnO (BNKT-BT-xZnO)) were synthesized by introducing ZnO nanoparticles. The results of the X-ray diffraction pattern (XRD) and energy dispersive spectroscopy (EDS) demonstrate that the majority of ZnO nanoparticles grow together to form enrichment regions, and the other Zn²⁺ ions diffuse into the matrix after sintering. With ZnO incorporated, the ferroelectric–ergodic relaxor transition temperature, T_F-R, and depolarization temperature, T_d, increase to above 120 °C and 110 °C, respectively. The research on temperature-dependent P–E loops verifies an attenuated ergodic degree induced by ZnO incorporation. For this reason, piezoelectric properties can be well-maintained below 110 °C. The electron backscatter diffraction (EBSD) was employed to investigate the stress effect. Orientation maps reveal the random orientation of all grains, excluding the impact of texture on depolarization. The local misorientation image shows that more pronounced strain appears near the boundaries, implying stress is more concentrated there. This phenomenon supports the hypothesis that potential stress suppresses depolarization. These results demonstrate that the depolarization behavior is significantly improved by the introduction of ZnO. The composites BNKT-BT-xZnO are promising candidates of lead-free ceramics for practical application in the future. Full article

Lead-free Na_1/2Bi_1/2TiO₃-BaTiO₃ (NBT-BT) has gained revived interest due to its exceptionally good high power properties in comparison to commercial lead-based piezoelectrics. Recently, Zn-modified NBT-BT-based materials as solid solution and composites have been reported to exhibit enhanced depolarization temperatures and a high mechanical quality factor. In this work, the pyroelectric properties of Zn-doped NBT-6mole%BT and NBT-9mole%BT ceramics are investigated. The doped compositions of NBT-6BT and NBT-9BT feature a relatively stable pyroelectric property in a wide temperature range of ~37 K (300–330 K) and 80 K (300–380 K), respectively. A threefold increase in detector figure of merit is noted for 0.01 mole Zn-doped NBT-6mole% BT at room temperature in comparison to undoped NBT-6mole%BT and this increase is higher than those of major lead-free materials. A broad range of the temperature-independent behavior for the figures of merit was noted (303–380 K) for Zn-doped NBT-6mole% BT, which is 30 K higher than the undoped material. The large pyroelectric figures of merit and good temperature stability renders Zn-doped NBT-BT an ideal candidate for pyroelectric detector and energy harvesting applications. Full article

The Podu Iloaiei Dam Lake located on the Bahluet River from Bahlui hydrographic basin, north-eastern Romania, is one of the most important water resources used for aquaculture activities in the region of interest. In the present study, the chemical composition related to water-soluble ions and elements was assessed in both water and sediment samples collected from the area of interest during July 2017 and October 2017, representative months for warm and cold seasons, respectively. Water-soluble ions (H₃C₂O₂⁻, HCO₂⁻, C₂O₄²⁻, F⁻, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, SO₄²⁻, Li⁺, Na⁺, NH₄⁺, K⁺, and Ca²⁺) were analyzed by ion chromatography, while inductively coupled plasma mass spectrometry was used to quantify water-soluble fractions of elements (Be, B, Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Mo, Ru, Pd, Ag, Cd, Sn, Sb, Te, Ba, Ir, Tl, Pb, Bi, and U). Evidence was obtained on the contributions of both anthropogenic and natural (pedologic) related sources in controlling the chemical composition of the water and sediment samples in the area. Analysis of Piper diagrams revealed the existence of CO₃²⁻/HCO₃⁻ and Ca²⁺/Mg²⁺ as dominant species for the sediment samples. The interest water pool was found to be oligotrophic over the warm period and eutrophic over the cold period. Overall, abundances and the association of chemical species in the area seemed to be controlled by a complex interplay between the water body’s main characteristics, meteorological factors, and anthropogenic activities. Moreover, the present results suggest that precautions should be taken for physicochemical parameter monitoring and prevention acts for surface water quality assurance in order to control the potential negative influence of some chemical parameters on fish productivity. Reported data also have a high potential to be used by experts in the field of developing lake water management policies for a sustainable exploitation of various aquatic systems. Full article

Recently, tricritical ferroelectrics have been drawn tremendous attention, owing to their ultrahigh dielectric permittivities of up to ε_r > 5 × 10⁴, and their consideration for prototype materials in the development of high-performance energy storage devices. Nevertheless, such a materials system suffers from the disadvantage of low breakdown strength, which makes its energy density far from the satisfactory level for practical application. In this paper, a material-modification approach has been reported, for improving the dielectric strength for tricritical ferroelectric materials Ba(Ti_1−xSn_x)O₃ (BTS) through doping with Bi_1.5ZnNb_1.5O₇ (BZN) additives. The results suggest that the electric strength has been largely improved in the modified tricritical ferroelectric material (BTS_x-yBZN), and the associated energy density reaches U_e = 1.15 J/cm³. Further microstructure investigation indicates that the modified tricritical ferroelectric material exhibits homogenous fine grains with perovskite structure in crystal symmetry, and the BZN may help to form a special structure that could enhance the breakdown strength. The findings may advance the material design and development of high-energy storage materials. Full article

Much attention is drawn to the preparation, structure and properties investigation of lead-free ferroelectrics for the next generation of piezoelectric devices. (Na_0.5Bi_0.5)TiO₃-BaTiO₃ (NBT-BT) lead-free solid solution piezoelectric single crystals with composition x in the range of 0–0.05 as a materials with high piezoelectric properties were successfully grown from platinum crucible by using the top-seeded solution growth (TSSG) method. The dimensions of NBT-BT crystal is Ø40 × 10 mm². X-ray powder diffraction patterns reveal that the crystal structure of NBT-BT crystal changes from rhombohedral to tetragonal symmetry with increasing amounts of BT(x). The dielectric, ferroelectric and piezoelectric properties of NBT-BT crystals with different compositions near the morphotropic phase boundary (MPB) were studied systematically. Ions (Mn, Eu, Zn) doped NBT and NBT-BT 95/5 crystals were also grown and studied. In addition, their piezoelectric and ferroelectric properties are investigated. Further, a high-quality and large-sized (K_0.25Na_0.75)NbO₃ (KNN25/75) single crystal has been achieved by a carefully controlled TSSG method. The dimensions of the as-grown KNN25/75 single crystal reached up to Ø30 × 10 mm². The obtained KNN crystals provided us a superb material for the dielectric, piezoelectric, ferroelectric and electromechanical coupling property characterization along different orientations. Full article

We have investigated the role of the Ti–O Coulomb repulsions in the appearance of the ferroelectric state in BaTiO3 as well as the role of the Zn–O Coulomb repulsions in BiZn0.5Ti0.5O3, using a first-principles calculation with optimized structures. In tetragonal BaTiO3, it is found that the Coulomb repulsions between Ti 3s and 3p states and O 2s and 2p states have an important role for the appearance of Ti ion displacement. In BiZn0.5Ti0.5O3, on the other hand, the stronger Zn–O Coulomb repulsions, which are due to the 3s, 3p, and 3d (d10) states of the Zn ion, have more important role than the Ti–O Coulomb repulsions for the appearance of the tetragonal structure. Our suggestion is consistent with the other ferroelectric perovskite oxides ABO3 in the appearance of tetragonal structures as well as rhombohedral structures. Full article

In this paper the characteristics of a CuO-BaTiO₃ based CO₂ gas sensor was investigated. The sensitivity of the CuO-BaTiO₃ based CO₂ sensor was influenced by doping various metal elements such as Au, Ag, Pt, Pd, Ce, Mg, Sr, La, Zn, Fe and Bi, which were added as a pure metal or in the form of metal oxides. It was found that Ag is the most suitable additive among all substances tested. The Ag-doped CO₂ gas sensor has better sensitivity and lower operating temperature, with a detection concentration range of from 100 ppm to 10%. The sensor also shows good stability. Full article