Browsing by Author "Vishnu Shankar Rai"

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Dielectric and electrical properties measurement of BCTO and Co & V-doped BCTO synthesized via semi-wet route method
(Springer, 2023) Anup Kumar; Vinod Kumar; Manish Kumar Verma; Vishnu Shankar Rai; Dinesh Prajapati; Biswajit Jena; Dipendra Kumar Verma; Poonam Kumari; D. Tiwary; K.D. Mandal
Bi2/3Cu3Ti4O12 (BCTO) and Bi2/3Cu3Ti3.95Co0.025V0.025O12 (BCTCVO) Ceramic was synthesized by using a cost-effective novel semi-wet route method. The phase formation was confirmed by XRD analysis with traces of TiO2 and CuO phases of BCTO and BCTCVO ceramic. The average crystallite sizes of BCTO and BCTCVO ceramic were found to be 40.49 and 39.72 nm, respectively. XPS studies confirm the oxidation state of each elements in appropriate oxidation state. Elemental analysis was performed by EDS. It was observed that the maximum dielectric constant values of BCTO and BCTCVO ceramic were 3372 and 1663 at 523 K and at 1 kHz. The value of dielectric constant was observed very low at higher frequency. Tangent loss values of BCTO and BCTCVO ceramic were found 3.67 and 2.39 at 523 K and 1 kHz, respectively. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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.
Emergence of Dielectric Properties by Doping of Semi-Transition Metal in Semiconductor Complex Perovskite Oxide
(John Wiley and Sons Inc, 2023) Vishnu Shankar Rai; Dinesh Prajapati; Manish Kumar Verma; Vinod Kumar; Atendra Kumar; Tapas Das; Kedar Sahoo; Narsingh Bahadur Singh; Kamdeo Mandal
The effect of zinc substitution at the Cu2+ site and germanium substitution at the Ti4+ site in bismuth copper titanate, Bi2/3Cu3Ti4O12, is investigated. Composition with x = 0.05 is synthesized by semi-wet route in the system Bi2/3Cu3Ti4−xGexO12 (BCTGO) and Bi2/3Cu3−xZnxTi4−xGexO12 (BCZTGO) that are sintered at 1123 K for 8 h. Crystal structure has remained cubic. The phase formations of these ceramics are confirmed by the X-ray diffraction. The microstructural analysis of the samples is done by scanning electron microscopy and tunneling electron microscopy. Elemental analysis is performed by energy dispersive X-ray spectroscopy. X-ray photoelectron spectroscopy suggests that all elements present in these ceramics are in proper oxidation states. The dielectric constant is found high for BCTGO-0.05 ceramic. The specific capacitances of BCTGO-0.05 and BCZTGO-0.05 are found to be 13.05 and 15.7 F g−1, respectively. Optical band gap values (Eg) of BCTGO-0.05 and BCZTGO-0.05 ceramics are found as 1.77 and 1.91 eV. © 2023 Wiley-VCH GmbH.
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.
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.
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.