Lead-based Materials Research Articles

First-principles study of polar magnets corundum double-oxides Mn2FeMO6 (M = W and Mo)

The physical properties of the corundum double-oxides Mn2FeMO6 (M = W and Mo) are investigated using density functional theory (DFT). The structure relaxation in different spin orders are performed and ferrimagnetic is found the most stable magnetic phase. The compounds are dielectric materials with band gap values 1.84 and 2.03 eV. These materials are polar magnets because of the coexistence of contradictory properties such as polarization and magnetization, which are observed very rarely. The electric polarization arises due structure distortion and cation orbital configuration of M atom, while the magnetization occurs due to unpaired dn of Mn and Fe orbital configuration. The compounds understudy are suitable for ferroelectric and magneto-electric applications due to their large spontaneous polarization (58.16 and 69.24 µC/cm2) and magnetic moments (3 and 3.43 µB/f.u). These multiferroic Mn2FeMO6 exhibit a profound interplay between electrical polarization and the applied magnetic field. The calculated values of piezoelectric coefficient, d33 = 264 and 606 pC/N are comparable to lead-based piezoelectric materials. A set of mechanical parameters revealed that Mn2FeMO6 are mechanically stable in rhombohedral phase. The applied strain has great influence on the physical properties of these two compounds.

Radiation-shielding properties of titanium dioxide-added composites

In radiation protection physics, development of alternative shielding materials to lead and lead-based materials is very popular nowadays, and thus, the present work aims to study the radiation-shielding parameters of a newly developed titanium dioxide (TiO2)-added hydroxyapatite composite material. The gamma-ray-shielding parameters were given in terms of the linear attenuation coefficient, half-value length, effective atomic number (Zeff) and effective electron density (Neff) for four different composites. The variations of these parameters with the titanium dioxide rate were also investigated.

Large electric-field induced strain in new ternary lead-free piezoelectric solid solution Na0.5Bi0.5TiO3-BaTiO3-Sr (Ta0.5Al0.5) O3

Ternary lead-free piezoelectric ceramics Na0.5Bi0.5TiO3-BaTiO3-Sr(Ta0.5Al0.5)O3 were synthesized via conventional solid-phase synthesis. All samples exhibited pure perovskite structure, indicating that Sr(Ta0.5Al0.5)O3 can be solidified into the Na0.5Bi0.5TiO3-BaTiO3 perovskite structure. The remanent polarization Pr and coercive field EC of the undoped Na0.5Bi0.5TiO3-BaTiO3 ceramic were Pr∼35.23µC/cm2 and EC∼42.46 kV/cm, respectively. The introduction of Sr(Ta0.5Al0.5)O3 sharply affected the ferroelectric properties of the substrate Na0.5Bi0.5TiO3-BaTiO3 ceramics. Increase in the content of Sr(Ta0.5Al0.5)O3 induces transition of this ternary system from a ferroelectric phase to an antiferroelectric-like phase, accompanied by double hysteresis loops in the 0.003SAT, 0.005SAT, and 0.01SAT components. The high dielectric constant ε′∼4300 was obtained for the 0.005SAT composition. The 0.015SAT composition yielded the maximum bipolar electric-field strain S (%) ∼0.53 % and high-field piezoelectric strain coefficient d33*∼ 996 pm/V. This result shows that a ternary Na0.5Bi0.5TiO3-BaTiO3-Sr(Ta0.5Al0.5)O3 solid solution is a promising alternative to lead-based piezoelectric materials in the field of high-performance actuators.

A Novel and Cost-Effective CsVO3 Quantum Dots for Optoelectronic and Display Applications.

Quantum dots (QDs) have an unparalleled ability to mimic true colors due to their size-tunable optical and electronic properties, which make them the most promising nanoparticles in various fields. Currently, the majority of QDs available in the market are cadmium, indium, and lead-based materials but the toxicity and unstable nature of these QDs restricts their industrial and practical applications. To avoid using heavy metal ions, especially cadmium, the current research is focused on the fabrication of perovskite and vanadate QDs. Herein, we report the facile synthesis of a novel and cost-effective CsVO3 QDs for the first time. The sizes of the CsVO3 QDs produced were tuned from 2 to 10 nm by varying the reaction temperature from 140 to 190 °C. On increasing QD size, a continuous red shift was observed in absorption and emission spectra, signifying the presence of quantum confinement. In addition, along with CsVO3 QDs, the CsVO3 nanosheets self-assembled microflower-like particles were found as residue after the centrifugation; the X-ray diffraction indicated an orthorhombic structure. Under 365 nm excitation, these CsVO3 microflower-like particles exhibited broad emission with CIE coordinates in the white emission region. The acquired results suggest that CsVO3 QDs may represent a new class of cadmium-free materials for optoelectronic and biomedical applications.

Electrocaloric effect in lead-free Ba1-xLn2x/3Ti0.925(Yb0.5Nb0.5)0.075O3 ceramics (Ln = Eu3+, Nd3+, Pr3+ and x = 0, 0.005)

This study reports on the electrocaloric effect in lead-free Ba1-xLn2x/3Ti0.925(Yb0.5Nb0.5)0.075O3 ceramics (where Ln = Eu3+, Nd3+, Pr3+), which was evaluated by an indirect method. The electrocaloric temperature change (ΔT) was estimated from the Maxwell relation based on measured P-E hysteresis loops recorded at different temperatures. For x = 0, the electrocaloric temperature change (ΔT) was about 0.052 K (7.95 kV/cm, 326 K), while they were 0.011 K (3.97 kV/cm and 338 K), 0.019 K (3.97 kV/cm and 332.5 K), and 0.622 K (28 kV/cm and 360 K) for the Eu 3+, Nd3+, and Pr3+ doped BaTi0.925(Yb0.5Nb0.5)0.075O3 (x = 0.005), respectively. The electrocaloric responsivity ξ = ΔT/ΔE, as calculated, reveals that the Ba0.995Pr0.005Ti0.925(Yb0.5Nb0.5)0.075O3 (BTYN: Pr3+) ceramic exhibits the largest value, of about 0.222 Kmm/kV, reported so far in the BTYN-based lead-free ceramics. As a result of this finding, the lead-free BTYN: Pr3+ system seems to be one of the best options for future electrocaloric applications as a lead-free alternative to lead-based materials.

PIEZOCERAMICS TECHNOLOGIES: APPROACHES FOR ENVIRONMENTAL IMPACT MITIGATION

The functional ceramic materials are broadly used in the electronic industry. Many of them are comprised of ferroelectric materials because of their outstanding piezoelectric and dielectric properties. Traditionally, the most popular piezoceramic materials are lead-based titanate-zirconate family (PZT), which have high values of piezoelectric properties. The negative aspect of PZT-based materials is associated with the toxic nature of lead. The toxicity of these materials makes their manufacturing and proper disposal difficult; hence, a new research direction has emerged to replace the lead-based materials with ceramic analogs containing no lead. Besides, the rising cost of energy and concerns about the environmental impact mitigation have necessitated more efficient and sustainable piezoceramics manufacturing processes. The ceramic industry is an energy-intensive industrial sector, and consequently, the potential to improve energy efficiency is enormous, mainly through the introduction of modern sintering tchnologies. Although toxicity and energy consumption are forms of environmental impact, strategies for managing each are different. While several technological approaches have been developed to reduce energy costs, there is a significant potential for improving environmental appeal of the process by introducing additive manufacturing methods, new sintering techniques and composites fabrication methods. This paper presents a brief analysis of the prospects for introducing 3D-printing methods in the production of piezoceramics and piezoelectric composites from the point of view of improving strategies for environmental impact mitigation.

The Recent Progress and the state-of-art applications of Perovskite Solar Cells

With the awareness of using clean and sustainable energy, the utilization of solar power is of great importance in human society. Following the trend, solar cells are required to have higher and higher power conversion efficiency. Contemporarily, perovskite materials, as a new type of materials for construction of solar cells, exhibits great potential to have high efficiency. This article focuses on the methods on improving power conversion efficiencies of perovskite solar cells and discusses the limitation of recent technologies and industrial applications, and the future prospect of perovskite solar cells. To be specific, all the methods are focusing on the selection of materials suitable for cells design, from CsSnI3 to lead-based organic materials, the efficiencies have increased significantly. The method of stacking perovskite solar cells to make tandem solar cells improved efficiencies among all the methods. Meanwhile, the toxicity, low stability and difficulties in large-scale application are the main limitations for perovskite solar cells. For the future studies, it is important to search for materials with low toxicity and high stability. The technology for improving efficiency of large-scale solar cells is also required. These results provide a guideline for the future study in perovskite solar cells.

Lead-Free BiFeO3-Based Piezoelectrics: A Review of Controversial Issues and Current Research State.

Lead-free electroceramics represent an emerging area of research that has the potential to enable new green advances in electronics. Research has mainly focused on the development of new piezoelectric materials for replacing lead containing oxides exhibiting superior electromechanical behavior. Lead-free BiFeO3-based materials are not only the promising candidates to replace lead-based materials but also show intriguing properties which may inspire innovative material design for the next generation of lead-free piezoceramics. This review aims to highlight the current state of research and overlooked aspects in lead-free BiFeO3-based ceramics, which could be insightful in elucidating certain controversial issues. Current strategies to reduce high conductivity, influence of chemical heterogeneity on both functional properties and crystal structure, effective heat treatment procedures, and the role of pseudo-cubic structures on the enhancement of piezoelectric properties are subjects of highlighted within this review as they have a significant impact on the quality of BiFeO3-based lead-free piezoelectrics (but are often disregarded).

Electromechanical Performance of Biocompatible Piezoelectric Thin-Films

The present study analyzed a computational model to evaluate the electromechanical properties of the AlN, BaTiO3, ZnO, PVDF, and KNN-NTK thin-films. With the rise in sustainable energy options for health monitoring devices and smart wearable sensors, developers need a scale to compare the popular biocompatible piezoelectric materials. Cantilever-based energy harvesting technologies are seldom used in sophisticated and efficient biosensors. Such approaches only study transverse sensor loading and are confined to fewer excitation models than real-world applications. The present research analyses transverse vibratory and axial-loading responses to help design such sensors. A thin-film strip (50 × 20 × 0.1 mm) of each sample was examined under volumetric body load stimulation and time-based axial displacement in both the d31 and d33 piezoelectric energy generation modes. By collecting evidence from the literature of the material performance, properties, and performing a validated finite element study to evaluate these performances, the study compared them with lead-based non-biocompatible materials such as PZT and PMN-PT under comparable boundary conditions. Based on the present study, biocompatible materials are swiftly catching up to their predecessors. However, there is still a significant voltage and power output performance disparity that may be difficult to close based on the method of excitation (i.e., transverse, axial, or shear. According to this study, BaTiO3 and PVDF are recommended for cantilever-based energy harvester setups and axially-loaded configurations.

A KNN composite-based piezoelectric helix for ultrasonic transcutaneous energy harvesting

Ultrasonic energy harvesting has been developed as a promising power solution for implantable medical devices (IMDs) to perform tasks such as diagnosis, therapy, and monitoring. However, most current ultrasonic electronics use toxic lead-based piezoelectric materials (e.g., lead zirconate titanate) as core components and feature bulk or flat structures, representing common barriers to the development of future IMDs that should be eco-friendly and long-term fixation in the implanted position. Here, we present a KNN composite-based lead-free piezoelectric helix for ultrasonic transcutaneous energy harvesting. The device contains multilayer components (a matching layer, lead-free composites, a copper foil, and a Parylene-C film) to form a final self-supporting helix harvester, which can adapt to cylindrical objects (e.g., blood vessels) to maintain fixation. Nanodomain-induced high-performance (d33 ∼ 465 pC N−1) KNN ceramic was fabricated and further processed into 1–3 composites to enhance electromechanical coupling properties and mechanical flexibility. The developed prototype can be excited ultrasonically to generate adjustable power output up to ∼22.97 mW cm−2. The generated electricity was stored in capacitors and used to operate light-emitting diodes. Further ex vivo tests showed that the device is still sufficient to support wireless energy transfer through porcine tissues, demonstrating the great potential of the lead-free piezoelectric helix for IMDs.

Pb-free halide perovskites for solar cells, light-emitting diodes, and photocatalysts

Metal halide perovskites have recently emerged as one of the most promising classes of semiconductors for various applications, especially in the field of optoelectronics. Lead-based halide perovskite materials, virtually unexploited for decades, have become prominent candidates due to their unique and intrinsic physicochemical and optical properties. Current challenges faced by the scientific community to capitalize on the properties of Pb-based perovskites are mainly associated with environmental concerns due to the toxicity of Pb and their poor stability. Under this context, over recent years, a number of new Pb-free halide perovskite (and perovskite-like) semiconductor classes have been introduced. This Perspective reviews recent developments in Pb-free halide perovskites, which specifically target their application in solar cells, light-emitting devices, and photocatalysts. Each type of Pb-free material is paired with a specific optoelectronic application, and the latest record performances are reported. Although these materials do not yet exhibit as attractive intrinsic optoelectronic properties as the Pb-based halide perovskites, their potential as alternatives for well-suited applications is discussed.

Effect of Stability of Two-Dimensional (2D) Aminoethyl Methacrylate Perovskite Using Lead-Based Materials for Ammonia Gas Sensor Application.

Changes in physical properties of (H2C=C(CH3)CO2CH2CH2NH3)2PbI2Cl2 and (H2C=C(CH3)CO2CH2CH2NH3)2Pb(NO3)2Cl2 (2D) perovskite materials from iodide-based (I-AMP) and nitrate-based (N-AMP) leads were investigated at different durations (days) for various storage conditions. UV-Vis spectra of both samples showed an absorption band of around λmax 420 nm due to the transition of n to π* of ethylene (C=C) and amine (NH2). XRD perovskite peaks could be observed at approximately 25.35° (I-AMP) and 23.1° (N-AMP). However, a major shift in I-AMP and dramatic changes in the crystallite size, FHWM and crystallinity percentage highlighted the instability of the iodide-based material. In contrast, N-AMP showed superior stability with 96.76% crystallinity even at D20 under the S condition. Both materials were exposed to ammonia (NH3) gas, and a new XRD peak of ammonium lead iodide (NH4PbI3) with a red-shifted perovskite peak (101) was observed for the case of I-AMP. Based on the FWHM, crystallite size, crystallinity and lattice strain analysis, it can be concluded N-AMP’s stability was maintained even after a few days of exposure to the said gases. These novel nitrate-based lead perovskite materials exhibited great potential for stable perovskite 2D materials and recorded less toxicity compared to famous lead iodide (PbI2) material.

Gamma-Ray Interaction of Selected Inorganic Scintillators Used in HEP Experiments

We attempted to study gamma-ray attenuation and sensing properties of conventional and modern inorganic scintillators being employed in the high energy physics (HEP) experiments. The mass attenuation coefficient (μm ), effective atomic number (Zeff ) and mean free path (mfp)were theoretically evaluated for the conventional scintillators materials such as CsI and NaI (Tl) and compared with advanced scintillator materials: PWO, PbF2, and BGO along with rare earth elements based scintillators such as LYSO:Ce, LuAG:Ce, BaF2:Y which have been proposed for applications in the future HEP experiments. Thegamma-ray attenuation parameters are analyzed within the framework of online software toolkit ‘py-MULBF’ over wide photon energy range from 0.015 MeV to 15 MeV.Variationof μm (and, Zeff ) with photon energy follows a trend similar for most of the inorganic scintillator materialsinvestigated here.CsI, however, maintained almost same effective atomic number value with respect to photon energy which signifies that CsI may be suitable for specific gamma-ray detection and sensing applications. Lead-based scintillator materials such as PbF2, PWO along with high-Z BGO are observed to exhibit better radiation attenuation capabilities.

Exploring Structural Nuances in Germanium Halide Perovskites Using Solid-State 73Ge and 133Cs NMR Spectroscopy.

Metal halide perovskites remain top candidates for higher-performance photovoltaic devices, but concerns about leading lead-based materials remain. Ge perovskites remain understudied for use in solar cells compared to their Sn-based counterparts. In this work, we undertake a combined 73Ge and 133Cs solid-state Nuclear Magnetic Resonance (NMR) spectroscopy and density functional theory (DFT) study of the bulk CsGeX3 (X = Cl, Br, or I) series. We show how seemingly small structural variations within germanium halide perovskites have major effects on their 73Ge and 133Cs NMR signatures and reveal a near-cubic phase at room temperature for CsGeCl3 with severe local Ge polyhedral distortion. Quantum chemical computations are effective at predicting the structural impact on NMR parameters for 73Ge and 133Cs. This study demonstrates the value of a combined solid-state NMR and DFT approach for investigating promising materials for energy applications, providing information that is out of reach with conventional characterization methods, and adds the challenging 73Ge nucleus to the NMR toolkit.

Structural, optical, and electrical properties of tin iodide-based vacancy-ordered-double perovskites synthesized via mechanochemical reaction

Over the recent past, lead-based halide perovskite materials have drawn significant attention due to their excellent optical and electrical properties for solar cells and optoelectronics applications. However, the toxicity of lead elements and instability under ambient conditions leads to develop alternative compositions. Herein, we report a novel mechanochemical synthesis of tin iodide-based double perovskites (A 2 SnI 6 ; A = Rb + , Cs + , methylammonium, and formamidinium), and their structural, optical, and electrical properties are investigated. Importantly, we found that the hydrogen iodide (HI) addition during the ball-milling process minimizes secondary phase formation in the synthesized A 2 SnI 6 powders. The effects of HI addition and the A-site substitution are investigated with respect to the lattice parameters, optical bandgaps, and electrical properties of the synthesized perovskite materials. Our results demonstrate essential information to improve the understanding of halide perovskite materials and develop efficient lead-free perovskite photoelectric devices.

Lead-Free Ultrasonic Phased Array Transducer for Human Heart Imaging.

Substantial advancement has been made in recent years on lead-free piezoelectric materials, but up to date, it is still a challenge to make a true medical imaging ultrasonic array transducer with center frequency <3 MHz. There are two major obstacles: the difficulty of fabricating large enough uniform lead-free piezoelectric materials with high piezoelectric coefficient, and the severe electrical impedance mismatch of an array element to the imaging system due to the relatively low dielectric constant of lead-free materials compared to lead-based piezoelectric materials. We resolved these two issues by employing texture engineering and stacking piezoelectric-layer design, which allowed us to fabricate an 80 element phased array transducer with the center frequency of 2.9 MHz and a bandwidth >80% for human heart imaging. The high-quality lead-free (Ba0.95Ca0.05)(Ti0.94Zr0.06)O3 textured ceramic plate has the size of 23×22×0.8 mm3 with the piezoelectric constant d33 = 570 pC/N. Phantom imaging and internal clinical human heart imaging demonstrated that this lead-free phased array can produce comparable imaging quality to that of a commercial PZT-5H ceramic-based phased array transducer, which demonstrated the practicality of using lead-free materials to replace PZT ceramics in phased array transducers for medical imaging applications.

Single-Beam Acoustic Tweezer Prepared by Lead-Free KNN-Based Textured Ceramics.

Acoustic tweezers for microparticle non-contact manipulation have attracted attention in the biomedical engineering field. The key components of acoustic tweezers are piezoelectric materials, which convert electrical energy to mechanical energy. The most widely used piezoelectric materials are lead-based materials. Because of the requirement of environmental protection, lead-free piezoelectric materials have been widely researched in past years. In our previous work, textured lead-free (K, Na)NbO3 (KNN)-based piezoelectric ceramics with high piezoelectric performance were prepared. In addition, the acoustic impedance of the KNN-based ceramics is lower than that of lead-based materials. The low acoustic impedance could improve the transmission efficiency of the mechanical energy between acoustic tweezers and water. In this work, acoustic tweezers were prepared to fill the gap between lead-free piezoelectric materials research and applications. The tweezers achieved 13 MHz center frequency and 89% −6 dB bandwidth. The −6 dB lateral and axial resolution of the tweezers were 195 μm and 114 μm, respectively. Furthermore, the map of acoustic pressure measurement and acoustic radiation calculation for the tweezers supported the trapping behavior for 100 μm diameter polystyrene microspheres. Moreover, the trapping and manipulation of the microspheres was achieved. These results suggest that the KNN-based acoustic tweezers have a great potential for further applications.

Investigation of solution-based synthesis of non-toxic perovskite materials using Mg, Ca, Mn, Fe, Cu, and Zn as the B-site cation for photovoltaic applications

High-efficiency perovskite solar cells are reliant on lead-based materials, which causes toxicity issues for large-scale implementation.

A critical review: the impact of electrical poling on the longitudinal piezoelectric strain coefficient

This review elaborates on the importance of poling and its theories, parameters, techniques andd33values of lead-based and lead-free materials and its composites. The energy-harvesting performance, current challenges, and prospects are also discussed.

Optimization based on computational analysis of lead-free inverted planar photo-voltaic device structure using halide based double perovskite material

Owing to the appealing optoelectrical, mechanical, and physical properties, configurable bandgaps, good performance on opaque devices, and low manufacturing cost, Perovskites solar cells are found to be the best alternatives for semi-transparent photo-voltaic (PV) applications. The high absorption coefficient, high carrier mobility, and long carrier diffusion length are inherent features of many organic and inorganic halide perovskite solar cells. Most of the promising perovskite materials contain Lead (Pb) and hence they are toxic. Besides toxicity issues, the stability of these perovskite structures is another key challenge in the process of its commercial production. The performance of various lead-free active PV materials was studied and identified that Cesium–Titanium Halide materials can be a suitable alternate for lead-based perovskite materials. These promising Cs2TiX6 materials have a tunable bandgap between 1.4 eV and 2.3 eV and have balanced electron and hole diffusion lengths. Most of the conventional PSC structure consists of regular planar N-I-P structure and the commercial applications of such devices are bounded due to very high J-V hysteresis and the need for high temperature during fabrication. The primary objective of this work is to optimize and develop an eco-friendly, highly efficient, Cesium-Titanium based novel inverted PV cell structure with all in-organic charge transport materials. The solar cell simulation program, SCAPS – 1D simulator, was used for conducting the numerical study and tested various device structures for obtaining maximum efficiency. The variations in the performance of PV cell structure were analyzed while using assorted absorber materials and inorganic charge transport materials. After the SCAPS-1D based simulation study, a high-performance PSC structure, FTO / MoO3 / Cs2TiBr6 / SnO2 / Au, was obtained. The proposed inverted PV cell structure can produce an excellent power conversion efficiency of 15.68 %, short-circuit current density of 16.59 mA/cm2, an open circuit voltage of 1.1 V, and a fill-factor of 85.76 %.