Browsing by Author "N.B. Singh"

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Dielectric and Electrical sensing behavior of undoped and doped complex perovskite oxide
(SPIE, 2023) Vishnu Shankar Rai; Shrikrishna Dutta Verma; Anup Kuma; K.D. Mandal; Meghan Brandt; N.B. Singh
CuY2Ti4O12 (CYTO) crystalline ceramic was successfully prepared through semi-wet route. The phase formation of CYTO ceramic was confirmed by powder X-ray diffraction studies with minor secondary phases formation of Y2O3 and Cu2Ti2O5. In the higher frequency section, the dielectric permittivity and tangent loss are temperature independent, whereas in the lower frequency section, these properties are temperature dependent. The dielectric constant of CYTO was determined as 1.2 x 104 at 100 Hz and 500 K. The dielectric loss of CYTO ceramic was found 0.75 at 10 kHz and 423 K. The dielectric constant and tangent loss both reduce with rising frequency in the lower frequency regions, while these are almost constant in the higher frequency regions. Impedance properties were used to check the grain and grain boundary phenomena in this ceramic. The presence of temperature dependent Maxwell-Wagner type relaxation was established by Impedance investigation of CYTO ceramic. © 2023 SPIE.
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.
Evolution of microstructure, dielectric, and electrical properties of Nd-doped BCTO synthesized via semi-wet route
(Springer Science and Business Media B.V., 2024) Dinesh Prajapati; Vishnu Shankar Rai; Biswajit Jena; Harish Verma; Atendra Kumar; N.B. Singh; K.D. Mandal
The Bi(2/3)-xNdxCu3Ti4O12 (BNCTO) ceramic with few selected concentrations (x = 0.05, 0.10, and 0.20) was fabricated through semi-wet route. The structural properties of synthesized compounds were examined using X-ray diffraction, followed by Rietveld refinement with a space group of Im-3. The crystallite size observed from X-ray diffraction was found in decreasing order with an increase in dopant concentration of Nd3+ ions in to BCTO ceramic. Scanning electron microscopy (SEM), energy-dispersive spectra (EDS), atomic force microscope (AFM), and X-photoelectron spectroscopy (XPS) were used to study the surface morphology, elemental compositions, surface roughness, and electronic state, respectively. Surprisingly, Nd doping can result in an exceptionally low dielectric loss (tan δ), with a minimum value of 0.05 at 1 kHz and 303 K for BNCTO-0.2. These findings show that Nd doping is more favorable to dielectric characteristics, introducing increased grain boundary resistance, activation energy, and lower conductivity. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
Low temperature processing of dielectric perovskites for energy storage
(SPIE, 2016) N.B. Singh; Ben Schreib; Michael Devilbiss; Julian Loiacono; Bradley Arnold; Fow-Sen Choa; K.D. Mandal
Since the report of high dielectric value was published for the calcium copper titanate of the stoichiometry CaCu3Ti4O12 (CCTO), several of its analogs such as Yittrium copper titanate Y2/3Cu3Ti4O12 (YCTO), Pr2/3Cu3Ti4O12 (PCTO) and several other compounds have been studied extensively. Most of these materials have demonstrated very high dielectric constants. However, the roadblock is their low resistivity. To overcome this problem, several approaches have been considered, including doping and substitution. In order to solve this problem, we have synthesized the stoichiometric composition and used low temperature processing to grow grains of La2/3Cu3Ti4O12 (LCTO) stoichiometric compound. LCTO with excess copper oxide was also prepared to determine its effect on the morphology and dielectric constant of the stoichiometric LCTO compound. In spite of the low melting point of copper oxide, we observed that excess copper oxide did not show any faster grain growth. Also, the dielectric constant of LCTO was lower than CCTO and unlike CCTO, LCTO showed significant changes as the function of frequency. The measured resistivity was slightly higher than CCTO. © 2016 SPIE.
Morphological evolution and transition at nanoscale in BSTO ceramic materials
(Taylor and Francis Ltd., 2023) N.B. Singh; Ching Hua Su; Fow-Sen Choa; Bradley Arnold; Brian Cullum; K.D. Mandal
Considerable efforts have been devoted since the past three decades for the development of low cost ferroelectric and clean energy storage multifunctional materials. Modification in design and production of a low cost material with well proven process provides pathway for high energy density dielectric energy storage. We studied fluorine doped a commercially well-established material system barium strontium titanate with two different concentrations of dopants and studied the morphological transition and its effect on properties. It was observed that sample with higher concentration transitioned much faster into glassy state, followed by growth of fibers which turned into a self-arranged bird nest type shape. The sample with lower concentration changed slowly into glassy state and only few fibers were farmed. Dielectric was highly dependent on processing methods and shows variation with crystallinity of material, temperature, and cooling conditions during processing. In the higher concentration range, we observed nano-scale interface breakdown very similar to that of solid-liquid interface breakdown during crystal growth. © 2023 Taylor & Francis Group, LLC.
Phase Evolution, Dielectric, and Electric Behavior of Sm-Doped BCTO Ceramic Fabricated by Semi-Wet Method
(John Wiley and Sons Inc, 2024) Dinesh Prajapati; Vishnu Shankar Rai; Atendra Kumar; N.B. Singh; Harish Verma; Shail Upadhyay; K.D. Mandal
Bi(2/3)-xSmxCu3Ti4O12 (BSCTO x = 0.05, 0.10, and 0.20) ceramics are synthesized using semi-wet technique and an extensive investigation into their structural, morphological, and elemental properties, alongside dielectric and impedance behaviors, is meticulously carried out. X-ray powder diffraction analysis unequivocally confirmed the formation of a monophasic BCTO cubic phase without any discernible secondary phases. and the crystallite size of the BSCTO ceramic, obtained by X-ray diffraction using Debye Scherrer formula, range from 62 to 81 nm. Rietveld analysis reveals that ceramics have a body centered cubic structure with space group Im-3. The Scanning electron microscope image displays the dense microstructure of the ceramics, while EDX analysis unveils the elemental composition of resulting products. Doping with Sm3+ induced a notable reduction in grain size, as observed through Scanning electron microscope and Atomic Force Microscope analyses, indicating Sm3+ hindered grain growth during sintering, potentially resulting in reduced dielectric constant (ε′). Dielectric constant and dielectric loss of the composition (x = 0.2) are found to be (Formula presented.) 152 and 0.04, respectively at room temperature (1 kHz). Impedance characteristics revealed a substantial increase in grain boundary resistance, leading to improved dielectric loss. The AC conductivity of BSCTO ceramics exhibited a frequency-dependent increase satisfying to Johncher's power law. © 2024 Wiley-VCH GmbH.
Progress in the growth of CaCu3Ti4O12 and related functional dielectric perovskites
(Elsevier Ltd, 2014) Laxman Singh; U.S. Rai; K.D. Mandal; N.B. Singh
Calcium copper titanate, CaCu3Ti4O12, (CCTO), a potential electro-ceramic is a member of a very important perovskite family and has been found to a show dielectric constant of the order of 10 4-105. It has a remarkable ability to undergo a series of cationic exchange reactions resulting in corresponding isomorphs. In the past decade there has been immense activity in the search of an isomorph of CCTO with high dielectric constant and low loss which enables its use as capacitor material for the storage of energy and miniaturization of electronic based equipment. Despite intensive research in the area there is no source of any literature that gives all the possible relevant information regarding various synthetic methods, characterizations, effect of sintering parameters (temperature, duration, and atmosphere). This review article is an effort to review the synthesis, grain growth, morphological evolution, effect of impurities, substitution and interface anisotropy on the dielectric constant, resistivity and other materials parameters. © 2014 Elsevier Ltd. All rights reserved.
The Effect of Rare Earth Metal Doping in Bi2/3Cu3Ti4O12 Ceramic on Microstructure, Dielectric and Electrical Properties
(Korean Institute of Electrical and Electronic Material Engineers, 2023) Dinesh Prajapati; Vishnu Shankar Rai; Vinod Kumar; Manish Kumar Verma; Atendra Kumar; N.B. Singh; K.D. Mandal
An Aurivillius oxide, Bi(2/3)-xGdxCu3Ti4O12 (x = 0.05, 0.10, and 0.20) ceramic designated as BGCTO-0.05, BGCTO-0.1 and BGCTO-0.2 has been fabricated by modified solid-state route resemble with semi wet route and characterized by using various techniques including XRD, SEM, EDX, TEM and XPS for getting information about phase formation, morphology, particle size distribution and oxidation state of elements of synthesized ceramics. X-ray diffraction pattern confirmed the single-phase formation of BGCTO ceramic. The crystalline nature of BGCTO ceramic for few selected compositions, x = 0.05, 0.10, and 0.20 were observed by TEM analysis. Further, particle size was determined with the help of Image J software and found to be 90.85 ± 5 nm, 75.35 ± 5 nm and 72.43 ± 5 nm, respectively for BGCTO-0.05, BGCTO-0.1 and BGCTO-0.2 ceramic. The dielectric permittivity (εr) as well as tangent loss (tan δ) was observed at room temperature and 1 kHz for all synthesized ceramics. The electrical behaviour of BGCTO ceramic revealed the presence of semiconducting grain separated by grain boundaries. © 2023, The Korean Institute of Electrical and Electronic Material Engineers.
The emergence of Griffiths phase in CaCu3Ti(4−x)Mn xO12 (CCTMO, x = 1, 2 and 3) geometrically frustrated antiferromagnetic complexes perovskite
(Springer, 2024) Vinod Kumar; Anup Kumar; Shruti Singh; Krishna Kumar; Manish Kumar Verma; Vishnu Shankar Rai; Gurudeo Nirala; Shail Upadhyay; Navneet Yadav; N.B. Singh; Dhanesh Tiwary; K.D. Mandal
In this work, we have reported the rare coexistence of a Griffiths phase (GP) in a complex perovskite oxide with geometrically frustrated antiferromagnetism. We have achieved this by substituting Manganese (Mn) in the titanium site of CaCu3Ti(4−x)MnxO12 (CCTMO, x = 1, 2 and 3). The occurrence of a Griffiths phase is observed when a strong contest between antiferromagnetic transition (TN) and paramagnetic (PM) occurs in the magnetic domain. As we increased the molar concentration of Manganese while substituting at titanium site in CaCu3Ti4O12, we observed the appearance of a step-like Griffiths phase. Manganese (Mn)-substituted materials exhibit paramagnetic (PM) to ferromagnetic (FM) phase transitions below CaCu3Ti3Mn1O12 (CCTM1O), CaCu3Ti2Mn2O12 (CCTM2O), and CaCu3Ti1Mn3O12 (CCTM3O), marked by a rapid step-like change in the magnetic moment due to spin ordering. The deviation of inverse magnetic susceptibility (χ−1) from Curie–Weiss behavior occurs in the temperature ranges of 75 to 190 K, 80 to 200 K, and 150 to 280 K, respectively. The emergence of the Griffiths phase before the actual PM–FM transition indicates that the inhomogeneous phase above the Curie temperature (T C), which can be defined as a Griffiths phase, is dominated by ferromagnetic interactions rather than antiferromagnetic ones. The presence of a Griffiths-like phase beyond its Curie temperature (T C) is indicated by low-field DC magnetization of the nanostructures, showing abnormal magnetic behavior. The presence of short-range magnetic correlations and ferromagnetic clusters in the system due to the size decrease is linked to this unexpected behaviour. © 2024, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.