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Papers by Abhigyan Dutta

Materials Letters: X, 2021

ADVANCED MATERIALS AND RADIATION PHYSICS (AMRP-2020): 5th National e-Conference on Advanced Materials and Radiation Physics, 2021

Nanostructured BaBi0.2Co0.35Fe0.45O3-δ (BBCF) was prepared using the citrate auto-ignition method... more Nanostructured BaBi0.2Co0.35Fe0.45O3-δ (BBCF) was prepared using the citrate auto-ignition method and sintered at different temperatures. Reitveld refinement of the XRD profiles indicated that the particle size and the microstrain show the opposite nature with the increase in sintering temperature. The FT-IR study confirmed different chemical bonds between the elements. The ionic conductivity of the samples decreased with theincrease in sintering temperature. The change in different structural, optical, and electrical properties due to variation in sintering temperature has been discussed and correlated.

Journal of Alloys and Compounds, 2020

Structural, optical and enhanced electrical properties of vanadium alloyed sodium bismuth titanat... more Structural, optical and enhanced electrical properties of vanadium alloyed sodium bismuth titanate solid solution synthesized by a chemical-mechanical hybrid method,

Materials Chemistry and Physics, 2021

Abstract A systematic study of transitional metal ion doped nickel-zinc ferrite (NZF) nanoparticl... more Abstract A systematic study of transitional metal ion doped nickel-zinc ferrite (NZF) nanoparticles with its magnetic properties and conductivity relaxation mechanism are the objectives of this research. We have prepared cobalt doped NZF nanoparticles (NZCo) via a facile chemical route. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analyses suggest the formation of single phase nearly spherical nanoparticles around 60 nm in size. UV–Vis study reveals the redshift of the optical band gap for doped samples. Estimation of particle size using the effective mass model agrees well with TEM/XRD results. The electrical modulus spectra have been analyzed using Harvilliak-Negami model function. Migration energy has been found to be the minimum for 10 mol % doped sample. Frequency-dependent modulus spectra have been converted to time domain data and the relaxation process shows Kohlrausch–Williams–Watts (KWW) type behavior. Carrier motion inside the lattice has been found to be strongly correlated. Room temperature magnetization curve shows that very weak AFM/PM contribution and strong FM interaction inside the system as well as non-collinear spin arrangements between interstitial sites. Law of Approach (L.A.) analysis of the AFM/PM part subtracted hysteresis curve delineates the enhanced magnetic properties such as saturation magnetization, anisotropy constant and coercivity. Multi-functional materials of such kind with optimum behavior at specific doping percentages can be fruitful for electronic industries.

Solid State Sciences, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

physica status solidi (a), 2018

In this work, structural, optical and electrical properties of Gd-doped Nickel ferrite nanocrysta... more In this work, structural, optical and electrical properties of Gd-doped Nickel ferrite nanocrystalline materials [NiFe 2Àx Gd x O 4 (x ¼ 0.00-0.15)] prepared through citrate auto-ignition method are reported. The X-ray diffraction (XRD) study reveals that prepared samples are purely single phase for lower Gd concentration but for higher Gd concentration, an orthorhombic phase of GdFeO 3 appears which is confirmed from Rietveld analysis. The UV-Vis study points to the semiconducting nature of the prepared samples. The electrical analysis shows that the ac conductivity of the samples increases with the increase in Gd doping concentration upto x ¼ 0.10 and then decreases. The dielectric relaxation process is analyzed using Havriliak-Negami formalism. The existence of small polaron hopping conduction is verified using Mott's variable range hopping model.

Materials Chemistry and Physics, 2019

Cobalt doped Ni-Zn ferrite nanoparticle (NZFC) were synthesized via citrate auto-ignition method ... more Cobalt doped Ni-Zn ferrite nanoparticle (NZFC) were synthesized via citrate auto-ignition method to investigate the structural correlations with microscopic length scale of charge transport in system. Impedance spectroscopy revealed that both grain and grain boundary have combined effect on the conductivity relaxation process. Temperature dependent dc conductivity showed Arrhenius behavior for both grain interiors and grain boundaries. Dielectric relaxation mechanism has been elucidated via Harviliak-Negami (H.N.) formalism. Two characteristic length scales i.e. mean square displacement and spatial extent of the charge carriers inside the system were calculated via standard methods. Microstructural parameters such as bond length, bond angles, bond valence sums (BVS) etc. were estimated by Rietveld refinement of the X-Ray Diffraction (XRD) data. Changes in microstructural parameters followed the same trend as the characteristic length scales with the variation of doping content. Optimum transport properties

Ceramics International, 2018

The aim of this work is to investigate the effect of divalent cations on the structure and electr... more The aim of this work is to investigate the effect of divalent cations on the structure and electrical properties of Ce 0.85 La 0.1 D 0.05 O 2-δ (D = Ca, Sr and Ba) oxygen ion conductors. The X-Ray structural analysis confirms the presence of CeDO 3 minor phase in addition to cubic fluorite phase of ceria in Sr 2+ and Ba 2+ added compositions. The lattice parameter of the compositions significantly depends on the ionic radius of dopants and the presence of D 2+ ions in ceria lattice. The Ca 2+ added composition shows the highest free oxygen vacancy concentration due to its lowest association energy and complete dissolution of Ca 2+ ions into ceria lattice. The dopant-vacancy association energy and grain interior conductivity changes with the ionic radii of the divalent dopants. The grain boundary capacitance depends on dielectric constant, grain size and grain boundary thickness. The grain boundary conductivity shows 46% over total conductivity for Sr 2+ added composition. The presence of CeDO 3 phase and space charge layer promotes the grain boundary resistances and affects the ion dynamics. Schematic models are proposed to understand the ion migration in grain boundaries. The scavenging effect is found to be highest in Sr 2+ ions added composition. The defect structures, the presence of CeDO3 phase and electrical properties are correlated with each other.

physica status solidi (a), 2018

Sm co-doped ceria-based ionic conductors are reported. The materials are prepared using citrate-a... more Sm co-doped ceria-based ionic conductors are reported. The materials are prepared using citrate-auto ignition method. The average particle size is found to be within 20 nm. The values of lattice parameter are found to depend on the ionic radius of dopants. Sm-Eu co-doped ceria shows the highest conductivity and lowest activation energy for the conduction. Pr-Sm co-doped ceria shows highest and Sm-Eu co-doped ceria shows lowest migration energy. The values of dc conductivity are found to be consistent with the charge carrier concentration. The relaxation phenomenon is investigated using Cole-Davidson formalism. The scaling behavior of complex impedance plots, impedance and modulus spectra confirm the temperature and dopant-independent conduction and relaxation mechanism. The impact of multivalency of Pr on conductivity and relaxation is also discussed.

Solid State Sciences, 2018

Abstract In this work, we investigate the structure, conductivity and ion dynamics of mixed di an... more Abstract In this work, we investigate the structure, conductivity and ion dynamics of mixed di and tri-valent doped Ce0.8Sm0.2-xSrxO2-δ (x = 0–0.2) oxygen ion conductors. The lattice parameter and root mean square strain are significantly affected by the ionic radius of dopants and their solubility into ceria lattice. Due to the solubility limit of Sr2+ ions, SrCeO3 phase increases with the doping concentration of Sr2+. The increase of Sr2+ ions into ceria lattice promotes the formation of large defect clusters by expense of formed oxygen vacancies. The coulombic interaction between oxygen vacancies with substituted dopant cations enhances with Sr2+ ions due to decrease of the value of dielectric constant of the compositions. The defect interaction significantly affects the conductivity values by means of increase of SrCeO3 phase and defect clusters. The conductivity values are found to be consistent with the migration and association energy. The scaled spectra of dielectric tangent loss and real part of complex conductivity confirm the temperature and defect interaction independent nature of hoping mechanism in the compositions.

Crystal Growth & Design, 2018

In the present work, polymorphic phase transformation of Bi 2 O 3 nano particles by the mechanica... more In the present work, polymorphic phase transformation of Bi 2 O 3 nano particles by the mechanical alloying method has been investigated in detail. X-ray diffraction study reveals that room temperature stable monoclinic α-phase of Bi 2 O 3 can be stabilized into body-centred cubic γphase by applying mechanical energy only to the Bi 2 O 3 powder, without adding any dopant to the Bi 2 O 3 matrix. Crystallite size of the γ-phase is reduced up to ~24 nm after 18 h of milling the analytical grade α-Bi 2 O 3 powder. Optical band gaps of all synthesized nanocrystalline powders are found to be in the semiconductor region (2.76 eV to 3.02 eV). Oxygen ion conductivity increases with the increase of γ-phase and becomes maximum in the 18h milled sample, in which full phase transformation (α to γ-phase) has occurred. Metastability of γ-phase is revealed on further mechanical alloying up to 20 h when milled powder decomposes primarily to α-phase along with other crystalline polymorphic phases which are identified by X-ray diffraction as well as Raman spectra. The temperature dependence of complex conductivity follows the Arrhenius relation and also supports the semiconducting nature of the sample as obtained by optical band gap measurement. The small polaron hopping between localized states are confirmed from the

Advanced Science Letters, 2016

Magnetic nanoparticles including ferrites are very potential candidatesfor its versatileapplicati... more Magnetic nanoparticles including ferrites are very potential candidatesfor its versatileapplication in the fields of engineering, bio medicine and electronics. Here we report the enhancement of magnetic properties of Mn-Ni co-doped cobalt ferrite nanoparticles which have been synthesized using coprecipitation technique. TEM study depicts the single phase nanocrystalline ferrite formation. Cation distribution between the tetrahedral and octahedral sites changes due to doping which is responsible for enhancement of magnetic properties. An exhaustive Rietveld analysis confirmed the rearrangement of the cations between the tetrahedral and octahedral sites. Also the results suggests strengthening of A-B and A-A interactions while weakening of B-B interaction for doped sample. "Law of Approach" technique is found to be usefuland utilized to extract the detailof magnetic parameters like anisotropy constant, anisotropy field, coercivity.

RSC Advances, 2016

Ion dynamics in pure and Dy containing nanoceria has been investigated in the light of different ... more Ion dynamics in pure and Dy containing nanoceria has been investigated in the light of different defect associates and their mutual interactions.

Journal of Physics and Chemistry of Solids, 2017

Abstract In this work, we have investigated the thermal, structural, optical and dielectric prope... more Abstract In this work, we have investigated the thermal, structural, optical and dielectric properties of Bi1−xDyxO1.5-δ (0.10≤x≤0.40) ionic conductors prepared by citrate auto-ignition method. The Thermo gravimetric-DTA analysis and X-Ray Diffraction pattern confirm the single δ-phase stabilization of doped system beyond 25 mol% doping concentration. XRD analysis also indicates that average crystallite size is maximum and micro strain is minimum for Bi0.75Dy0.25O1.5-δ composition. The optical band gap of the prepared compositions is obtained from the Ultraviolet- Visible spectroscopy that shows a red shift with the increase in Dy content. The presence of different structural bonds is confirmed from FT-IR spectroscopy analysis. Ionic transport property of the prepared compositions has been analyzed using Nyquist plot for dc conduction and Nernst-Einstein relation for ac conduction mechanism. This analysis indicates that the composition Bi0.75Dy0.25O1.5-δ shows highest conductivity. The dielectric properties of these ionic conductors have been analyzed using Havriliak–Negami (HN) formalism. The dielectric permittivity e ' ( ω ) of all the prepared compositions is found to be within the range 1.61–3.63(x102) in S.I. unit. Analysis of electric modulus data reveals that dielectric and modulus relaxation follows same mechanism. The time-temperature superposition principle has been verified from the scaling of modulus spectra.

Journal of Alloys and Compounds, 2015

Enhancement of magnetic moment as well as magnetocrystalline anisotropy constants is very much re... more Enhancement of magnetic moment as well as magnetocrystalline anisotropy constants is very much required for the device application of cobalt ferrites. We are able to achieve enhanced magnetic properties of nanocrystalline cobalt ferrite by virtue of suitable doping. Pure, Mn and Ni doped cobalt ferrite nanoparticles have been synthesized using facile soft chemical route. XRD analysis using Rietveld refinement technique confirms the growth of pure, single phase cobalt ferrite nanoparticles, corroborates with TEM study. The observed increase in saturation magnetization for the doped samples can be attributed to the migration of Co 2+ ions from B site to A site and hence Fe 3+ ions from A site to B site. Detailed magnetic analysis using Law of Approach shows an increase of different magnetic properties like anisotropy constant, anisotropy field, coercivity for the doped samples, could be due to the increase in magnetic interaction between two sites due to different cation distribution. A structure property correlation has been established by proposing a cation distribution which enables us to explain the enhancement of magnetic properties.

Materials Research Bulletin, 2017

Microstructure, optical and ionic transport properties of chemically derived Ce 1Àx Pr x O 2Àd (0... more Microstructure, optical and ionic transport properties of chemically derived Ce 1Àx Pr x O 2Àd (0.05 x 0.2) has been investigated in this work. Rietveld analyses of the X-ray diffraction patterns showed that, microstructural parameters depend on Pr content as well as sintering temperature. The High Resolution-Transmission Electron Microscopy together with Rietveld analyses confirmed the cubic fluorite structure of the samples. The Scanning Electron Microscope images showed gradual grain growth due to sintering. The Energy Dispersive X-ray spectra showed decrease of oxygen content with Pr concentration. The direct optical band gap was found to show a red shift with dopant concentration and sintering temperature. The conductivity has been found to have strong dependency on the oxidation of Pr 3+ to Pr 4+ , impurity, oxygen vacancy concentration, defect association and charge carrier concentration and found to obey Variable Range Hopping phenomenon. The ion dynamics has been correlated with the structural changes due to Pr doping.

In this paper we report dc and ac electrical properties of some Nd-doped ZnO nanocrystals prepare... more In this paper we report dc and ac electrical properties of some Nd-doped ZnO nanocrystals prepared through a modified ceramic route. The X-ray diffraction (XRD) study reveals that prepared samples are single phase, pure nanocrystalline ZnO. The ac and dc conductivity measurements showed that the dc conductivity of the samples decreases with the increase in Nd doping concentration. The results are being explained in the light of band theoretical approach.

Materials Letters: X, 2021

ADVANCED MATERIALS AND RADIATION PHYSICS (AMRP-2020): 5th National e-Conference on Advanced Materials and Radiation Physics, 2021

Nanostructured BaBi0.2Co0.35Fe0.45O3-δ (BBCF) was prepared using the citrate auto-ignition method... more Nanostructured BaBi0.2Co0.35Fe0.45O3-δ (BBCF) was prepared using the citrate auto-ignition method and sintered at different temperatures. Reitveld refinement of the XRD profiles indicated that the particle size and the microstrain show the opposite nature with the increase in sintering temperature. The FT-IR study confirmed different chemical bonds between the elements. The ionic conductivity of the samples decreased with theincrease in sintering temperature. The change in different structural, optical, and electrical properties due to variation in sintering temperature has been discussed and correlated.

Journal of Alloys and Compounds, 2020

Structural, optical and enhanced electrical properties of vanadium alloyed sodium bismuth titanat... more Structural, optical and enhanced electrical properties of vanadium alloyed sodium bismuth titanate solid solution synthesized by a chemical-mechanical hybrid method,

Materials Chemistry and Physics, 2021

Abstract A systematic study of transitional metal ion doped nickel-zinc ferrite (NZF) nanoparticl... more Abstract A systematic study of transitional metal ion doped nickel-zinc ferrite (NZF) nanoparticles with its magnetic properties and conductivity relaxation mechanism are the objectives of this research. We have prepared cobalt doped NZF nanoparticles (NZCo) via a facile chemical route. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analyses suggest the formation of single phase nearly spherical nanoparticles around 60 nm in size. UV–Vis study reveals the redshift of the optical band gap for doped samples. Estimation of particle size using the effective mass model agrees well with TEM/XRD results. The electrical modulus spectra have been analyzed using Harvilliak-Negami model function. Migration energy has been found to be the minimum for 10 mol % doped sample. Frequency-dependent modulus spectra have been converted to time domain data and the relaxation process shows Kohlrausch–Williams–Watts (KWW) type behavior. Carrier motion inside the lattice has been found to be strongly correlated. Room temperature magnetization curve shows that very weak AFM/PM contribution and strong FM interaction inside the system as well as non-collinear spin arrangements between interstitial sites. Law of Approach (L.A.) analysis of the AFM/PM part subtracted hysteresis curve delineates the enhanced magnetic properties such as saturation magnetization, anisotropy constant and coercivity. Multi-functional materials of such kind with optimum behavior at specific doping percentages can be fruitful for electronic industries.

Solid State Sciences, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

physica status solidi (a), 2018

In this work, structural, optical and electrical properties of Gd-doped Nickel ferrite nanocrysta... more In this work, structural, optical and electrical properties of Gd-doped Nickel ferrite nanocrystalline materials [NiFe 2Àx Gd x O 4 (x ¼ 0.00-0.15)] prepared through citrate auto-ignition method are reported. The X-ray diffraction (XRD) study reveals that prepared samples are purely single phase for lower Gd concentration but for higher Gd concentration, an orthorhombic phase of GdFeO 3 appears which is confirmed from Rietveld analysis. The UV-Vis study points to the semiconducting nature of the prepared samples. The electrical analysis shows that the ac conductivity of the samples increases with the increase in Gd doping concentration upto x ¼ 0.10 and then decreases. The dielectric relaxation process is analyzed using Havriliak-Negami formalism. The existence of small polaron hopping conduction is verified using Mott's variable range hopping model.

Materials Chemistry and Physics, 2019

Cobalt doped Ni-Zn ferrite nanoparticle (NZFC) were synthesized via citrate auto-ignition method ... more Cobalt doped Ni-Zn ferrite nanoparticle (NZFC) were synthesized via citrate auto-ignition method to investigate the structural correlations with microscopic length scale of charge transport in system. Impedance spectroscopy revealed that both grain and grain boundary have combined effect on the conductivity relaxation process. Temperature dependent dc conductivity showed Arrhenius behavior for both grain interiors and grain boundaries. Dielectric relaxation mechanism has been elucidated via Harviliak-Negami (H.N.) formalism. Two characteristic length scales i.e. mean square displacement and spatial extent of the charge carriers inside the system were calculated via standard methods. Microstructural parameters such as bond length, bond angles, bond valence sums (BVS) etc. were estimated by Rietveld refinement of the X-Ray Diffraction (XRD) data. Changes in microstructural parameters followed the same trend as the characteristic length scales with the variation of doping content. Optimum transport properties

Ceramics International, 2018

The aim of this work is to investigate the effect of divalent cations on the structure and electr... more The aim of this work is to investigate the effect of divalent cations on the structure and electrical properties of Ce 0.85 La 0.1 D 0.05 O 2-δ (D = Ca, Sr and Ba) oxygen ion conductors. The X-Ray structural analysis confirms the presence of CeDO 3 minor phase in addition to cubic fluorite phase of ceria in Sr 2+ and Ba 2+ added compositions. The lattice parameter of the compositions significantly depends on the ionic radius of dopants and the presence of D 2+ ions in ceria lattice. The Ca 2+ added composition shows the highest free oxygen vacancy concentration due to its lowest association energy and complete dissolution of Ca 2+ ions into ceria lattice. The dopant-vacancy association energy and grain interior conductivity changes with the ionic radii of the divalent dopants. The grain boundary capacitance depends on dielectric constant, grain size and grain boundary thickness. The grain boundary conductivity shows 46% over total conductivity for Sr 2+ added composition. The presence of CeDO 3 phase and space charge layer promotes the grain boundary resistances and affects the ion dynamics. Schematic models are proposed to understand the ion migration in grain boundaries. The scavenging effect is found to be highest in Sr 2+ ions added composition. The defect structures, the presence of CeDO3 phase and electrical properties are correlated with each other.

physica status solidi (a), 2018

Sm co-doped ceria-based ionic conductors are reported. The materials are prepared using citrate-a... more Sm co-doped ceria-based ionic conductors are reported. The materials are prepared using citrate-auto ignition method. The average particle size is found to be within 20 nm. The values of lattice parameter are found to depend on the ionic radius of dopants. Sm-Eu co-doped ceria shows the highest conductivity and lowest activation energy for the conduction. Pr-Sm co-doped ceria shows highest and Sm-Eu co-doped ceria shows lowest migration energy. The values of dc conductivity are found to be consistent with the charge carrier concentration. The relaxation phenomenon is investigated using Cole-Davidson formalism. The scaling behavior of complex impedance plots, impedance and modulus spectra confirm the temperature and dopant-independent conduction and relaxation mechanism. The impact of multivalency of Pr on conductivity and relaxation is also discussed.

Solid State Sciences, 2018

Abstract In this work, we investigate the structure, conductivity and ion dynamics of mixed di an... more Abstract In this work, we investigate the structure, conductivity and ion dynamics of mixed di and tri-valent doped Ce0.8Sm0.2-xSrxO2-δ (x = 0–0.2) oxygen ion conductors. The lattice parameter and root mean square strain are significantly affected by the ionic radius of dopants and their solubility into ceria lattice. Due to the solubility limit of Sr2+ ions, SrCeO3 phase increases with the doping concentration of Sr2+. The increase of Sr2+ ions into ceria lattice promotes the formation of large defect clusters by expense of formed oxygen vacancies. The coulombic interaction between oxygen vacancies with substituted dopant cations enhances with Sr2+ ions due to decrease of the value of dielectric constant of the compositions. The defect interaction significantly affects the conductivity values by means of increase of SrCeO3 phase and defect clusters. The conductivity values are found to be consistent with the migration and association energy. The scaled spectra of dielectric tangent loss and real part of complex conductivity confirm the temperature and defect interaction independent nature of hoping mechanism in the compositions.

Crystal Growth & Design, 2018

In the present work, polymorphic phase transformation of Bi 2 O 3 nano particles by the mechanica... more In the present work, polymorphic phase transformation of Bi 2 O 3 nano particles by the mechanical alloying method has been investigated in detail. X-ray diffraction study reveals that room temperature stable monoclinic α-phase of Bi 2 O 3 can be stabilized into body-centred cubic γphase by applying mechanical energy only to the Bi 2 O 3 powder, without adding any dopant to the Bi 2 O 3 matrix. Crystallite size of the γ-phase is reduced up to ~24 nm after 18 h of milling the analytical grade α-Bi 2 O 3 powder. Optical band gaps of all synthesized nanocrystalline powders are found to be in the semiconductor region (2.76 eV to 3.02 eV). Oxygen ion conductivity increases with the increase of γ-phase and becomes maximum in the 18h milled sample, in which full phase transformation (α to γ-phase) has occurred. Metastability of γ-phase is revealed on further mechanical alloying up to 20 h when milled powder decomposes primarily to α-phase along with other crystalline polymorphic phases which are identified by X-ray diffraction as well as Raman spectra. The temperature dependence of complex conductivity follows the Arrhenius relation and also supports the semiconducting nature of the sample as obtained by optical band gap measurement. The small polaron hopping between localized states are confirmed from the

Advanced Science Letters, 2016

Magnetic nanoparticles including ferrites are very potential candidatesfor its versatileapplicati... more Magnetic nanoparticles including ferrites are very potential candidatesfor its versatileapplication in the fields of engineering, bio medicine and electronics. Here we report the enhancement of magnetic properties of Mn-Ni co-doped cobalt ferrite nanoparticles which have been synthesized using coprecipitation technique. TEM study depicts the single phase nanocrystalline ferrite formation. Cation distribution between the tetrahedral and octahedral sites changes due to doping which is responsible for enhancement of magnetic properties. An exhaustive Rietveld analysis confirmed the rearrangement of the cations between the tetrahedral and octahedral sites. Also the results suggests strengthening of A-B and A-A interactions while weakening of B-B interaction for doped sample. "Law of Approach" technique is found to be usefuland utilized to extract the detailof magnetic parameters like anisotropy constant, anisotropy field, coercivity.

RSC Advances, 2016

Ion dynamics in pure and Dy containing nanoceria has been investigated in the light of different ... more Ion dynamics in pure and Dy containing nanoceria has been investigated in the light of different defect associates and their mutual interactions.

Journal of Physics and Chemistry of Solids, 2017

Abstract In this work, we have investigated the thermal, structural, optical and dielectric prope... more Abstract In this work, we have investigated the thermal, structural, optical and dielectric properties of Bi1−xDyxO1.5-δ (0.10≤x≤0.40) ionic conductors prepared by citrate auto-ignition method. The Thermo gravimetric-DTA analysis and X-Ray Diffraction pattern confirm the single δ-phase stabilization of doped system beyond 25 mol% doping concentration. XRD analysis also indicates that average crystallite size is maximum and micro strain is minimum for Bi0.75Dy0.25O1.5-δ composition. The optical band gap of the prepared compositions is obtained from the Ultraviolet- Visible spectroscopy that shows a red shift with the increase in Dy content. The presence of different structural bonds is confirmed from FT-IR spectroscopy analysis. Ionic transport property of the prepared compositions has been analyzed using Nyquist plot for dc conduction and Nernst-Einstein relation for ac conduction mechanism. This analysis indicates that the composition Bi0.75Dy0.25O1.5-δ shows highest conductivity. The dielectric properties of these ionic conductors have been analyzed using Havriliak–Negami (HN) formalism. The dielectric permittivity e ' ( ω ) of all the prepared compositions is found to be within the range 1.61–3.63(x102) in S.I. unit. Analysis of electric modulus data reveals that dielectric and modulus relaxation follows same mechanism. The time-temperature superposition principle has been verified from the scaling of modulus spectra.

Journal of Alloys and Compounds, 2015

Enhancement of magnetic moment as well as magnetocrystalline anisotropy constants is very much re... more Enhancement of magnetic moment as well as magnetocrystalline anisotropy constants is very much required for the device application of cobalt ferrites. We are able to achieve enhanced magnetic properties of nanocrystalline cobalt ferrite by virtue of suitable doping. Pure, Mn and Ni doped cobalt ferrite nanoparticles have been synthesized using facile soft chemical route. XRD analysis using Rietveld refinement technique confirms the growth of pure, single phase cobalt ferrite nanoparticles, corroborates with TEM study. The observed increase in saturation magnetization for the doped samples can be attributed to the migration of Co 2+ ions from B site to A site and hence Fe 3+ ions from A site to B site. Detailed magnetic analysis using Law of Approach shows an increase of different magnetic properties like anisotropy constant, anisotropy field, coercivity for the doped samples, could be due to the increase in magnetic interaction between two sites due to different cation distribution. A structure property correlation has been established by proposing a cation distribution which enables us to explain the enhancement of magnetic properties.

Materials Research Bulletin, 2017

Microstructure, optical and ionic transport properties of chemically derived Ce 1Àx Pr x O 2Àd (0... more Microstructure, optical and ionic transport properties of chemically derived Ce 1Àx Pr x O 2Àd (0.05 x 0.2) has been investigated in this work. Rietveld analyses of the X-ray diffraction patterns showed that, microstructural parameters depend on Pr content as well as sintering temperature. The High Resolution-Transmission Electron Microscopy together with Rietveld analyses confirmed the cubic fluorite structure of the samples. The Scanning Electron Microscope images showed gradual grain growth due to sintering. The Energy Dispersive X-ray spectra showed decrease of oxygen content with Pr concentration. The direct optical band gap was found to show a red shift with dopant concentration and sintering temperature. The conductivity has been found to have strong dependency on the oxidation of Pr 3+ to Pr 4+ , impurity, oxygen vacancy concentration, defect association and charge carrier concentration and found to obey Variable Range Hopping phenomenon. The ion dynamics has been correlated with the structural changes due to Pr doping.

In this paper we report dc and ac electrical properties of some Nd-doped ZnO nanocrystals prepare... more In this paper we report dc and ac electrical properties of some Nd-doped ZnO nanocrystals prepared through a modified ceramic route. The X-ray diffraction (XRD) study reveals that prepared samples are single phase, pure nanocrystalline ZnO. The ac and dc conductivity measurements showed that the dc conductivity of the samples decreases with the increase in Nd doping concentration. The results are being explained in the light of band theoretical approach.