Browsing by Author "Laxman Singh"

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A Brief Review of the Current Scenario on the Synthesis and Application of TIO, Nanoparticles
(Bentham Science Publishers, 2025) Sudhakar Saroj; Laxman Singh; Satya Vir Singh
TiO2 nanomaterials can be synthesized in various types of structures, such as nano-powder, nano-films, nano-rods, nano-crystals, etc., by various methods such as biological, precipitation, hydrothermal, electrochemical, solvothermal, spray pyrolysis, co-precipitation, micro-emulsion, solution-combustion, and sol-gel, etc. Each method has unique importance, merits, and demerits. Such as biological method is an eco-friendly method and avoids toxic chemicals in the preparation of TiO₂-based nanomaterials. The co-precipitation technique is very convenient and easy, but its control over size distribution is not good, which results in coarser particles instead of nanoparticles. The micro-emulsion method facilitates good control over the particle size by the ratio of surfactant to water, low reaction temperature, and short processing time. The sol-gel method has high homogeneity in crystals, better tuning over the shape and size of the crystals with reasonable preparation cost. The hydrothermal and solvothermal processes have good chemical uniformity and a higher probability of synthesizing unique metastable structures at minimum reaction temperatures but nanomaterials synthesized via these methods are not stable for application at the higher temperature. The electrochemical technique facilitates a multifaceted and minimum temperature method to synthesize TiO, nanoparticles with good control over crystallite size, better yield, and negligible environmental effect. To synthesize the nanostructures of TiO₂, liquid phase processing is the most convenient method since it gives better homogeneity in the product with good control over shape and size. In this chapter, short literature regarding the synthesis of TiO₂ nanostructure by various methods and its applications are discussed. Moreover, the regeneration of used TiO₂-based nanoparticles is also reported. © 2025, Bentham Books imprint.
A Novel Rhodamine Probe Acting as Chemosensor for Selective Recognition of Cu2+ and Hg2+ Ions: An Experimental and First Principle Studies
(Springer, 2024) Pawan Kumar Sada; Amit Bar; Amanpreet Kaur Jassal; Prabhat Kumar; S. Srikrishna; Alok Kumar Singh; Sumit Kumar; Laxman Singh; Abhishek Rai
Copper and Mercury ions have vital role to play in biological world as their excess or deficiency can cause different type of diseases in human being as well as biological species including plants and animals. Therefore, their detection at trace level becomes very important in term of biological. The current studies embody the fabrication, structural characterization and recognition behavior of a novel rhodamine B hydrazone formed when hydrazide of rhodamine B was condensed with 5-Allyl-3-methoxy salicylaldehyde (RBMA). RBMA was found to be responsive towards the very trace level of Cu2+ and Hg2+ among other tested cations so far. The sensing procedure is based on the classical opening of the spiroatom ring of rhodamine. The limit of detection (LOD) and binding constant is 5.35 ppm, 2.06 × 104 M−1 and 5.16 ppm, 1.26 × 104 M−1 for Cu2+ and Hg2+ ions respectively. The probable mechanism correlates the specific binding of RBMA with Cu2+ and Hg2+ ions. The 1:1 stoichiometry of RBMA with Cu2+ and Hg2+ ions have been supported by HRMS, FT-IR data, Job's plot, and binding constant data. Reversibility is well exhibited by RBMA by the involvement of CO32− ions via demetallation process. The real time application is well demonstrated by the use of paper strip test. The DFT study also carried out which agrees well with the experimental findings. The results displayed the novelty of this current work towards the trace level analysis of the Cu2+ and Hg2+ of the cations which are play the crucial role in industry. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2023.
Beneficiation of iron and aluminium oxides from fly ash at lab scale
(Elsevier, 2015) Ram Singh; Laxman Singh; Satya Vir Singh
During electricity production, the fly ash (FA) is generated from the combustion process and it is a pollutant. Present investigation was carried out for the recovery of iron oxide and alumina from fly ash. The fly ash was subjected to magnetic separation where part of iron oxide was separated. After this the fly ash was leached with hydrochloric acid followed by precipitating the leached liquor with ammonia hydroxide to get hydroxides of alumina and iron which are dehydrated at high temperature (1100°C) to obtain iron and aluminium oxides as a mixed powder. Leaching of alumina and iron oxides from fly ash with hydrochloric acid, the effects of four parameters viz. acid concentration and acid to fly ash ratio, leaching temperature and time were investigated and optimum conditions were (i) concentration of HCl 6 N, (ii) fly ash (g) to HCl acid (ml) ratio 1:4, (iii) temperature of leaching 107°C, and (iv) duration of leaching 5 h. The total recoveries of iron oxide and aluminium oxide were 63% and 73%, respectively. © 2015 Elsevier B.V.
Citric acid-assisted inexpensive semi-wet combustion synthesis and characterization of ultrafine LiFeinf0.95/infTiinf0.05/infPOinf4/inf and LiFePOinf4/inf polycrystalline materials
(Pan Stanford Publishing Pte. Ltd., 2022) Laxman Singh; Dev Kumar Mahato; R.N. Rai; Ashok Kumar Gupta; Youngil Lee
[No abstract available]
Combustion synthesis of nanostructured Ba0.8(Ca,Sr)0.2TiO3 ceramics and their dielectric properties
(Elsevier Ltd, 2015) Laxman Singh; Ill Won Kim; Byung Cheol Sin; Uma Shanker Rai; Seung Ho Hyun; Youngil Lee
Ba0.8(Ca,Sr)0.2TiO3 nanostructured ceramics were synthesized by a facile and glycine-assisted auto-combustion method using stable solid TiO2, which is better than other several chemical routes reported earlier involving expensive alkoxides, oxynitrates, or chlorides of titanium as the titanium sources. TGA/DSC analysis of precursor powder gives pre-information about formation of final product around 950 °C. XRD analysis confirms the formation of single-phase of the BCT and BST ceramics on sintering at 950 °C for 15 h. TEM image of the ceramics show nanocrystalline particles in the range 40–90 nm. Surface morphology indicates that the average grain size is in range of 55–140 nm and 45–120 nm for BCT and BST, respectively. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirmed the purity and stoichiometry. The value of the dielectric constant of BST (εr~368) ceramic is higher than BCT (εr~255) at 100 Hz at 308 K. The dielectric constant BST is higher than BCT at all measured temperatures and frequency ranges due to higher crystallinity and high grain-boundary resistance, as confirmed by impedance analysis. © 2015 Elsevier Ltd and Techna Group S.r.l.
Comparative Dielectric and Ferroelectric Characteristics of Bi0.5Na0.5TiO3, CaCu3Ti4O12, and 0.5Bi0.5Na0.5TiO3–0.5CaCu3Ti4O12 Electroceramics
(Springer New York LLC, 2016) Laxman Singh; Shiva Sundar Yadava; Byung Cheol Sin; Uma Shanker Rai; K.D. Mandal; Youngil Lee
Abstract: The dielectric and ferroelectric characteristics of Bi0.5Na0.5TiO3 (BNT), CaCu3Ti4O12 (CCTO), and 0.5Bi0.5Na0.5TiO3–0.5CaCu3Ti4O12 (BNT/CCTO) ceramics are compared. X-ray diffraction patterns confirmed the formation of single phase of all the ceramics after sintering at 950°C for 15 h. Scanning electron microscopy images of the sintered ceramics reveal average grain sizes in the range from 200 nm to 2.5 μm. Energy-dispersive x-ray mapping and x-ray photoelectron spectroscopy show the presence of the elements Bi, Na, Ca, Cu, Ti, and O with uniform distribution in the ceramics. BNT/CCTO exhibits high dielectric constant (εr ∼ 6.9 × 104) compared with BNT (εr ∼ 0.13 × 104) and CCTO (εr ∼ 1.68 × 104) ceramics at 1 kHz and 503 K. The high dielectric constant of BNT/CCTO compared with BNT and CCTO is associated with a major contribution from grain boundaries, as confirmed by impedance and modulus analyses. The P–E hysteresis loop of all the ceramics measured at room temperature and 50°C exhibited typical ferroelectric nature. The remanent polarization (Pr) of BNT (1.58 μC/cm2) and CCTO (0.654 μC/cm2) ceramics are higher than that of BNT/CCTO (0.267 μC/cm2) ceramic. Graphical Abstract: [Figure not available: see fulltext.] © 2016, The Minerals, Metals & Materials Society.
Comparative dielectric studies of nanostructured BaTiO3, CaCu3Ti4O12 and 0.5BaTiO3· 0.5CaCu3Ti4O12 nano-composites synthesized by modified sol-gel and solid state methods
(Elsevier Inc., 2014) Laxman Singh; Uma Shanker Rai; Kam Deo Mandal; Byung Cheol Sin; Hyung-Il Lee; Hoeil Chung; Youngil Lee
BaTiO3 (BTO), CaCu3Ti4O12 (CCTO) and 0.5BaTiO3·0.5CaCu3Ti4O 12 (BTO-CCTO), as a new nano-composite ceramic, were successfully designed and fabricated by a semi-wet gel route and a modified solid state method. The dielectric properties of the BTO-CCTO ceramic were compared to those of the BTO and CCTO ceramics at lower sintering temperatures and durations. The X-ray diffraction analysis revealed that the BTO and CCTO ceramics form a single crystalline phase and the average crystalline sizes calculated from X-ray diffraction data were in the range of 40-65 nm. The particle sizes of the BTO, CCTO, and BTO-CCTO ceramics obtained from transmission electron microscopy images were in the ranges of 40-65 nm, 80-110 nm, and 70-95 nm, respectively. The phase composition and microstructure were studied by X-ray diffraction and scanning electron microscopy. The energy dispersive X-ray results demonstrated the purity and stoichiometry of the BTO-CCTO nano-composite. The grain sizes of the BTO, CCTO and BTO-CCTO ceramics were found to be in the ranges of 500 nm-1 μm, 4-24 μm, and 250 nm-4 μm, respectively. The AC conductivity as a function of frequency confirmed the semiconducting nature of all of the ceramics and obeyed the Jonscher's power law. The impedance spectrum measurement result showed that the CCTO ceramic possessed an exceptional grain boundary resistance, which supports the internal barrier layer capacitance (IBLC) mechanism present in this ceramic and is responsible for the high εr values. © 2014 Elsevier Inc. All rights reserved.
Development of a new rhodamine 6G based probe and its application as an optical sensor of Cu2+ and Fe3+ ions: A comprehensive experimental and Theoretical studies
(Elsevier Inc., 2024) Pawan Kumar Sada; Amanpreet Kaur Jassal; Amit Bar; Prabhat Kumar; S. Srikrishna; Sumit Kumar; Alok Kumar Singh; Youngil Lee; Laxman Singh; Abhishek Rai
A new rhodamine appended probe 3-allyl salicylaldehyde rhodamine hydrazone (RGAL) has been synthesized and thoroughly characterized using various spectroscopic techniques, as well as single crystal XRD. The optical properties of RGAL were investigated in 10 mM HEPES buffer in H2O:CH3CN (2:8, v/v, pH=7.2) in the presence of various cations. RGAL showed selectivity and sensitivity towards Cu2+ during absorption process and “turn on” behavior towards Fe3+ during emission study owing to the opening of a spirolactum ring. The detection limits for Cu2+ and Fe3+ ions using RGAL were determined to be 6.15 ppm and 4.75 ppm, respectively. The binding constant of RGAL with Cu2+ and Fe3+ ions was found to be 1.20 × 104 M−1 and 1.71 × 104 M−1, respectively. Hirshfeld surface and fingerprint analysis of RGAL provides the in-depth analysis of pairwise interaction between two atoms. Furthermore, the topological analysis of RGAL is performed using NCI, AIM, ELF and LOL analysis. The analysis provides information about O78-H79…N71 and C40-H41…O77 hydrogen bonding interactions in the monomer of RGAL whereas various inter- and intra- molecular interactions give strength to the dimer pattern of RGAL. © 2024 Elsevier B.V.
Dielectric and ac impedance studies of nanostructured CaCu 3Ti3.90Ce0.10O12 electro-ceramic synthesized by citrate-gel route
(2013) K.D. Mandal; Laxman Singh; Sunita Sharma; U.S. Rai; M.M. Singh
Effect of doping at Ti4+ site by Ce3+ has been examined in CaCu3Ti3.90Ce0.10O12 synthesized by citrate-gel route. DTA/TG analysis of dry powder gives pre-information about formation of final product around 850 C. X ray diffraction analysis confirmed the formation of CaCu3Ti3.90Ce 0.10O12 phase of the ceramic sintered at 950 C for 12 h. Microstructure has been studied using scanning electron microscopy and confirmed the average grain size found in nano range 200-400 nm in system CaCu 3Ti3.90Ce0.10O12.The nature of relaxation behavior of ceramic was also rationalized by using the impedance and modulus spectroscopy. The bulk conductivity indicates an Arrhenius-type thermally activated process. The ac conductivity spectrum obeyed the Jonscher power law. The complex impedance diagrams of the ceramic exhibited a significant contribution from the grains, grain boundaries and electrode. The activation energies calculated from the grain-boundary relaxation time constant was found to be 0.49 eV which confirmed the Maxwell-Wagner type of relaxation present in the ceramic. © 2013 Springer Science+Business Media New York.
Dielectric behavior of CaCu3Ti4O12 electro-ceramic doped with La, Mn and Ni synthesized by modified citrate-gel route
(Tsinghua University, 2013) Laxman Singh; U.S. Rai; Alok Kumar Rai; K.D. Mandal
The effect of La3+, Mn2+ and Ni2+ doped calcium copper titanate, CaCu3Ti4O12 (CCTO), at higher concentrations (CR1 and CR2 with 5 mol% and 10 mol%, respectively), has been examined by semi-wet route at relatively lower temperature. This semi-wet route employs citrate-nitrate gel chemical method using TiO2 solid powders. X-ray diffraction (XRD) analysis confirms the formation of single phase in the doped samples sintered at 900 °C for 8 h. Scanning electron micrographs (SEM) show that the average grain size for CR2 is larger than that of CR1 composition. The energy dispersive X-ray spectroscopy (EDX) is used to study the percentage compositions of different ions present in both ceramics. Dielectric constant (ɛr) and dielectric loss (tanδ) values of CR1 are comparatively higher than those of CR2 ceramic at all measured frequencies and temperatures. The nature of temperature-dependent relaxation behavior of the ceramics is also studied by impedance, modulus spectroscopic analysis and confirms Maxwell-Wagner relaxation. © 2013, The Author(s).
Dielectric properties of CaCu3-xMgxTi4O12 (x=0.20 and 0.50) material synthesized by the semi-wet route for energy storage capacitor
(SPIE, 2019) Laxman Singh; U.S. Rai; N.B. Singh; Y. Lee; D.K. Mahato; Divyanshu Bhardwaj; K.D. Mandal
Dielectric properties of high percentage Mg doped CaCu3Ti4O12, CaCu3-xMgxTi4O12 (x=0.20 and 0.50) ceramics carried out. They were synthesized by the semi-wet route using a solution based citrate-nitrate method along with inexpensive solid TiO2 powder. X-ray diffraction analysis reveals that the ceramics form single phase when sintered at 950 °C for 12h. SEM analyses show the smooth surfaces of grains with a spherical appearance. The grains of CCMTO2 and CCMTO5 ceramics were found to be in the size range of 1-5 μm and 1-3 μm, respectively. Dielectric studies show that the CCMTO2 ceramic has higher value of dielectric constant and lower dielectric loss in comparison to that of CCMTO5. © 2019 SPIE. Downloading of the abstract is permitted for personal use only.
Dielectric properties of zinc doped nanocrystalline calcium copper titanate synthesized by different approach
(2013) Laxman Singh; U.S. Rai; K.D. Mandal
Zinc doped calcium copper titanate, CaCu2.90Zn 0.10Ti4O12 (CCZTO), nanocrystalline electro-ceramics synthesized by solution-wet route (SR) as well as semi-wet route using citric acid (SWR1) and glycine (SWR2) separately, were characterized by TGA/DTA, XRD, TEM, SEM and EDX techniques. The crystallite sizes of the ceramics obtained by XRD were found to be in the range of 45-90 nm is in good agreement with those observed by TEM analysis. The grain sizes for the ceramics SWR1, SWR2 and SR observed by SEM were found in the range of 10-15 μm, 1-4 μm, and 2-4 μm, respectively. Thermal studies show that the single phase CCZTO ceramic was formed in single step combustion reaction in SWR2 while in the case of SWR1 and SR were obtained in multistep reactions. SWR2 route shows more effective solid state reaction for the formation of nanocrystalline CCZTO single phase at much lower sintering temperature. SWR1 ceramic exhibits higher dielectric constant (εr ∼ 4317) than SWR2 and SR ceramics at room temperature. © 2013 Elsevier Ltd.
Dielectric studies of a nano-crystalline CaCu2.90Zn0.10Ti4O12 electro-ceramic by one pot glycine assisted synthesis from inexpensive TiO2 for energy storage capacitors
(Royal Society of Chemistry, 2014) Laxman Singh; Ill Won Kim; Byung Cheol Sin; Kam Deo Mandal; Uma Shanker Rai; Amir Ullah; Hoeil Chung; Youngil Lee
A facile way for the synthesis of nano-crystalline CaCu2.90Zn0.10Ti4O12 (CCZTO) using a solution combustion technique based on the glycine-nitrate process with inexpensive solid TiO2 powder as the raw material is introduced in this manuscript, for the first time. The precursor powder was calcined between 200 °C and 850°C for 3 h in air. Phase formation, crystalline nature, morphology and chemical purity of the fabricated CCZTO were investigated with TG/DTA, FT-IR, FT-Raman, XRD, SAED patterns, SEM, TEM, EDX and XPS analyses, respectively. The XRD results indicated that all sintered samples had a major CaCu3Ti4O12 structure with some amount of CaTiO3 and CuO. The bright-field TEM micrographs revealed that the particle size was in the range of 15-50 nm, which was in good agreement with the average crystallite size obtained from XRD. SEM micrographs of the sintered CCZTO ceramics showed the average grain sizes were in the range of 800 nm-7 μm. EDX and XPS studies confirmed the stoichiometry and purity of the ceramics. The nature of the relaxation behavior of the ceramics was rationalized using impedance and modulus spectroscopy. The activation energies calculated from the grain-boundary relaxation time constant were found to be in the range of 0.79-0.52 eV, which confirmed the Maxwell-Wagner type of relaxation present in the ceramic. Our inexpensive novel solution chemistry based method for CCZTO-16h gives a high dielectric constant (799) and low dielectric loss (0.091) at 100 Hz at room temperature, which has potential significance for cost-effective technological applications in microelectronic devices. © the Partner Organisations 2014.
Dielectric, AC-impedance, modulus studies on 0.5BaTiO3·0. 5CaCu3Ti4O12 nano-composite ceramic synthesized by one-pot, glycine-assisted nitrate-gel route
(Elsevier Ltd, 2014) Laxman Singh; Uma Shanker Rai; Kamdeo Mandal; Byung Cheol Sin; Sang-Ick Lee; Youngil Lee
A nano-composite electro-ceramic with the chemical formula 0.5BaTiO 3·0.5CaCu3Ti4O12 (BTO-CCTO) has been synthesized by a glycine - assisted nitrate-gel route which is simpler and faster at relatively low temperature than the conventional solid-state synthesis method. X-ray diffraction (XRD) analysis showed the existence of BTO as a secondary phase alongside the major phase of CCTO. Transmission electron microscope (TEM) analysis of the composite shows that nano-particles (60±15 nm) were obtained. Further, scanning electron microscope (SEM) images show that the morphology consists of a few large grains of CCTO (∼1-5 μm) embedded in small grains of BTO (∼500 nm-1 μm) with a bimodal distribution. The impedance analysis shows two major contributions associated with the grains and the grain boundaries. Modulus analysis of this composite confirmed the presence of a Maxwell-Wagner type relaxation, which is temperature dependent. The activation energy value was found to be 0.80 eV, and this composite is electrically conductive due to the mobility of the ionized oxygen defects. © 2014 Elsevier Ltd and Techna Group S.r.l.
Effect of processing routes on microstructure, electrical and dielectric behavior of Mg-doped CaCu3Ti4O12 electro-ceramic
(2013) Laxman Singh; U.S. Rai; K.D. Mandal; Alok Kumar Rai
In the present communication, data on magnesium-doped calcium copper titanate CaCu2.90Mg0.10Ti4O12 (CCMTO) electro-ceramic, synthesized by the semi-wet route (SWR), ball-milled route (BMR) and solid-state route (SSR), is characterized by TG-DTA, XRD, SEM, EDX and TEM techniques. XRD confirmed the formation of single phase in CCMTO ceramic. The CuO phase present at grain boundaries in SWR ceramic was shown by the SEM micrograph, which was verified by EDX. The TEM image of SWR ceramic shows nanocrystalline particles in the range 80±20 nm. The value of the dielectric constant of SWR (ε r ∼20091) ceramic is higher than those of BMR and SSR (ε r ∼1247) ceramics at 1 kHz at 450 K. A dielectric relaxation has been observed in the frequency range 100 Hz-100 kHz. The high-temperature dielectric dispersion shows one large low-frequency response and two Debye-type relaxations. The impedance and modulus studies show the highest grain-boundary resistance for BMR ceramic. © 2012 Springer-Verlag Berlin Heidelberg.
Exploring the recognition behavior of a fluorescein-based probe towards the significant detection of Cu2+ and Zn2+ ions: Experimental and computational studies
(Elsevier B.V., 2025) Navneet Kumar; Pawan Kumar Sada; Amit Kumar Kundan; Amit Bar; Amanpreet Kaur Jassal; Surya Prakash Rai; Vipendra Kumar Singh; Neha Garg; Alok Kumar Singh; Ankit Kumar Singh; Sumit Mohan Kumar; Laxman Singh; Abhishek Rai
A new fluorescein hydrazone (FA1) has been synthesized employing fluorescein hydrazide and 3,5-diiodosalicylaldehyde and its complete physiochemical characterization have been carried out. A single crystal XRD studies of FA1 has been performed. Among the tested metal ions FA1 significantly detects Cu2+ and Zn2+ in EtOH/H2O (8:2, v/v)). There is an emergence of a new absorbance peak at λmax 431 nm with Cu2+ ions. A “turn-on” behavior in fluorescence at λem510 nm was observed with Zn2+ ions owing to chelation enhanced fluorescence. This act of spectrophotometric changes and naked eye color variation from colorless to yellow is because of coordination with the metal ions rather than most common opening of spirolactum ring. FA1-Cu2+ and FA1-Zn2+ensembles display reversible behavior with EDTA2− ions. In a study on latent fingerprint detection using powder compounds, it was found that FA1 and FA1–Zn2+ showed excellent adherence to finger ridges and produced clear features without any background stains. The Hirshfeld surface and fingerprint analysis of FA1 offer a detailed examination of pairwise interactions between atoms. Additionally, topological analysis of FA1 has been conducted using NCI, AIM, ELF, and LOL methodologies. Alamar assay of FA1 on HEK-293 cell lines exhibited biocompatibility with minimal cytotoxicity. Hence, they were effectively applied for live cell imaging for intracellular sensing of Cu2+ and Zn2+ in HEK-293 cells. © 2025 Elsevier B.V.
Future perspectives on QDs embedded nano-fibrous materials as high capacity sustainable anode for Na-ion batteries technology
(Springer Nature, 2023) Sunil Kumar; R.N. Rai; Darshan Singh; Anees A. Ansari; Youngil Lee; Laxman Singh
Abstract: Electrode functionalization (shape-selective materials) has transformed the energy storage and production technology in the modern age of developing Batteries science. Sodium-ion batteries are promising electrochemical energy supply system suitable alternative to Li-ion batteries, particularly for low cost, earth abundance Na ion, high structural stability, and better functioning behavior at cooler temperatures. In Na-ion batteries (NIBs), lowest potential electrode (negative electrode) act as primary charge carrier and thermodynamically susceptible to reduce alkali Na +. However, conventional anode material suffers from volume variation and stability issues. Quantum dots (QDs) size (1–10 nm) supported nanofiber (1D) functions as high rate redox-active materials due to synergistic interaction and structural confinement effect. Present perspective shed light on various structural interactions, thermodynamic interactions and interfaces which may lower the energy barrier (activation energy) during electrode electrochemical performance. Quantum dots provide functional sites in nanofiber resulting in expansion of Na+ storage and sodiation reaction. Thus, structural and chemical variation unveil future research for high capacity, robust Na+ storage, and better thermodynamic stability of fibrous Na-ion anode materials to upgrade the futuristic electrode technology. Graphical abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to The Materials Research Society.
Insights into solid solution-assisted polyanion cathodes: Present status, environmental focus and advancement in phosphate and borate chemistry for Li- and Na-ion battery technologies
(Elsevier Ltd, 2025) Laxman Singh; Sunil Kumar; Rajeev Kumar; V. Srivastva; Mikhael Bechelany; Youngil Lee
The development of high energy-density and low-cost alkali-ion batteries is critically important for future portable electronics, heavy electric vehicles, and grid storage. Polyanion solid solution cathodes that are chemically functionalized through molecular or atomic nano-engineering and possess unique microstructures would offer significantly enhanced electro-chemical properties for commercial prospects due to their high energy density, specific capacity, facile ion-diffusion, high safety, and superior structural stability under low or high temperature environments. The low molecular weight borates have a great potential to form the desirable polyanion solid solution than the other mature polyanion families, i.e., PO43−, SiO44-, CO32-, SO42- etc. The beauty of borate chemistries have been revealed owing to its smaller formula mass (58.8), low reaction energy, anti-oxidation, and robust polyanionic structure which make them suitable for composite interaction. In addition, these composites are superior hosts for Li+ or Na+ per formula unit, multi-electron redox chemistry and stoichiometric composition, thereby preventing rapid capacity and voltage decay via the coupling effects of cathode active components. The present review explores the recent progress of solid solution based polyanion nanomaterials containing BO33- and PO43− polyanions which also includes physico-chemical characteristics of Zn, Cu, Co, Mn, Fe and V-based polyanionic materials. Moreover, there are no literature reported so far on the Zn, Cu, and Co-based borate polyanions for Li- and Na-ion batteries (LIBs and NIBs). However, unlike phosphate based electrodes, there are very few review articles published on Li-ion batteries using borate materials. Therefore, this review provides the extensive literature on the solid composites containing BO33- or mixed-borate polyanions, and their comparison with phosphate cathodes which would inculcate deeper outlook for the safer design and development of high energy-density LIBs and NIBs. © 2024 Elsevier B.V.
Investigation of dielectric, mechanical, and electrical properties of flame synthesized Y2/3Cu2.90Zn0.10Ti4O12 material
(Springer New York LLC, 2018) Laxman Singh; Muhammad Sheeraz; Mahmudun Nabi Chowdhury; U.S. Rai; Shiva Sunder Yadava; Young Seok Park; Satya Vir Singh; Youngil Lee
A simple flame synthesis method was used to fabricate the Y2/3Cu2.90Zn0.10Ti4O12 (YCZTO) material. The X-ray diffraction analysis showed the single-phase formation of the YCZTO material directly sintered at 1050 °C for 15 h. Scanning electron microscopy showed well packed grains with high densification of morphology having the average grain size in range of 0.8–4 µm. X-ray photoelectron spectroscopy analysis showed that the Cu and Zn are in + 2 valence state confirming the Zn successfully incorporated at Cu2+ site. YCZTO exhibited the εr value of ∼ 1.4 × 103 and dielectric loss (tan δ) of ∼ 0.09 at 50 °C. The impedance spectroscopy analysis suggested that the obtained YCZTO material is electrically heterogeneous. The activation energies (Ea) for conduction at the grain boundaries at higher temperature range (110–150 °C) were found to be in the range ∼ 1.0 eV. Besides the dielectric property, YCZTO also showed the interesting mechanical and I–V characteristics. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
Low-cost flame synthesized La2/3Cu3Ti4O12 electro-ceramic and extensive investigation on electrical, impedance, modulus, and optical properties
(Elsevier Ltd, 2023) Laxman Singh; Lokeswararao Dhavala; Rajasekhar Bhimireddi; Anees A. Ansari; Sunil Kumar; Vandana Srivastava; R.N. Rai; Quyet Van Le; Youngil Lee
An environmentally-friendly synthesis route and low-cost starting materials are more appropriate for the production of ceramic materials at the industry level. With this concern we prepared the La2/3Cu3Ti4O12(LCTO), which is isostructural of CaCu3Ti4O12 (CCTO), using the low-cost TiO2 instead of a high-cost of titanium source (titanium isopropoxide or titanium chloride) using a low-cost wet-chemical route. Although, there are lots of synthetic methods reported for LCTO fabrication in terms of duration, cheap reagents, energy consumption, feasibility, etc. The present method is far better than the others. The prepared ceramic samples were sintered at 1050 °C/12 h and studied their structural, morphology and impedance, and modulus studies for further confirmation. The prepared LCTO ceramic shows the pure phase with the cubic type of morphology. The homogenous distribution of all the elements was observed through dispersive X-ray analysis. X-ray photoelectron spectroscopy studies revels that La is in +3 oxidation state, Cu is in a +2 oxidation state, and Ti is multiple (+3 and + 4) oxidation state. The LCTO ceramic displayed the very high dielectric constant (∼3852) and dielectric loss (0.322), at 1 kHz and at room temperature. Calculated the activation energy using the impedance and modulus data and it shows the superior to that of CCTO ceramic synthesized by the same method. The prepared samples exhibited Debye-type relaxation, which is evoked from the impedance and modulus studies. The calculated optical energy bandgap of LCTO (2.06 eV) is found to be lesser than that of the well-known structure of perovskites (BaTiO3 (3.28 eV), PbTiO3 (3.18 eV), LiNbO3 (3.78 eV) and BiFeO3 (2.67 eV) as well as structure of spinel CoCr2O4 (3.10 eV) and LuFe2O4 (2.18 eV)) materials. © 2023 Elsevier Ltd and Techna Group S.r.l.