Verified email at gmail.com
Associate Professor, Research Centre and PG Department of Physics
The Madura College, Madurai - 625 011
M.Sc., M.Phil., Ph.D.
Materials, Ceramics, Ferro, Piezo,...
M. Thavarani, M. Charles Robert, N. Pavithra, R. Saravanan, Y. B. Kannan, and S. Balaji Prasath
Journal of Materials Science: Materials in Electronics, ISSN: 09574522, eISSN: 1573482X, Pages: 4116-4131, Published: March 2022 Springer Science and Business Media LLC
The phase pure Ca2+-doped ZnFe2O4, spinel ferrite, synthesized by solvothermal method were analyzed using X-ray diffraction data. The structure factor corresponding to miller lattice planes and parameters like cell constants, anion positional parameter (O2−), etc., are calculated using Rietveld refinement strategy, considering cubic spinel structure. The cation distribution study reveals mixed spinel structure with both Ca2+ and Fe3+ ions occupying both tetrahedral A site and octahedral B site and Zn2+ occupying only at tetrahedral A site. The quantitative and visual electron bonding study reveals covalent bonding between A site ions and O2− ions and ionic bonding between B site ions and O2− ions for all the compositions and both are dominating for the composition Ca0.2Zn0.8Fe2O4. Also, the maximum entropy method-based electron density studies reveals that A–B interaction is maximum compared to A–A and B–B interactions and A–A interaction is the weakest one. The surface morphology using SEM shows spherical particle nature and energy dispersive X-ray analysis shows its stoichiometric compositions without any impurity elements. The magnetic properties are analyzed using vibrating sample magnetometer, which reveals the prepared sample with composition Ca0.2Zn0.8Fe2O4 show good ferromagnetic properties at room temperature. The observed saturation magnetization, remanent magnetization, coercivity and squareness ratio (Mr/Ms) for the composition Ca0.2Zn0.8Fe2O4 are 32.588 emu/g, 9.4265 emu/g, 407.98 gauss, and 28.95%, respectively. The present work reveals that Ca0.2Zn0.8Fe2O4 may be one of the best alternative low-cost and environment friendly semi-hard ferrite, useful in high-frequency device applications.
Muthaian Charles Robert, Nagaraj Pavithra, Ramachandran Saravanan, and Subramanian Saravanakumar
Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences, ISSN: 09320784, Published: 2022 Walter de Gruyter GmbH
Abstract Tin(II) sulfide (SnS) is a low symmetric orthorhombic double-layered dual bandgap semiconductor. It is low cost, toxic-free and highly abundant on Earth, with multifunctional optical, electronic, magnetic and light conversion applications when doped adequately with impurity. These physical properties can be understood only by the complete understanding of microstructural properties like average structure, electron density distribution inside the unit cell, bonding nature and local structure. In this work, the average and local structure, along with the electron density distribution of a nano crystallite sized single-phase sample of tin(II) sulfide is elucidated with the help of precise X-ray intensity data. The average structural information was extracted using Rietveld refinement analysis and the visual mapping of 3D, 2D and 1D electron density distribution inside the unit cell and its numerical contribution using maximum entropy method (MEM). The bonding between the first inter and intra bonding between Sn and S atoms is 2.65,105 Å and 3.2689 Å with mid bond electron density 0.907 e/Å3 and 0.1688 e/Å3 respectively. The inter-atomic correlations of 1st, 2nd and 3rd nearest neighbour atoms, their bond length, and the crystallite size are reported from pair distribution function (PDF) analysis using low Q-XRD data (Q ∼ 6.5 Å−1). The PDF analysis shows that the first and second nearest Sn–S bonding distance is 2.6064 Å and 3.4402 Å, first is between the Sn and S atoms of the same layer and the other between the Sn and S atoms of the adjacent layers respectively.
M. Thavarani, M. Charles Robert, S. Balaji Prasath, N. Pavithra, R. Saravanan, and S. Saravanakumar
Journal of Electronic Materials, ISSN: 03615235, eISSN: 1543186X, Published: 2022 Springer Science and Business Media LLC
A clear understanding of the microstructural and physical properties of materials is an essential requirement for the advancement of industrial device applications. In this context, single-phase spinel Co2+ -doped ZnFe2O4 (CoxZn1-xFe2O4: x = 0.05, 0.10, 0.15, 0.20) was synthesised by autocombustion and characterised structurally and magnetically by x-ray and vibrating-sample magnetometry (VSM), respectively. Scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) were used for surface morphology and elemental composition analysis. UV-Visible spectrophotometry was used for optical band gap analysis. Rietveld refinement study yielded the refined structure factor for each Bragg plane, cell constant and oxygen positional parameter. Both cation distribution analysis and VSM studies revealed a cubic spinel structure with a partial distribution of Fe3+ ions at the tetrahedral A and octahedral B sites and the complete incorporation of Co2+ and Zn2+ ions at the octahedral B site. The bonding strength and electron density distribution between tetrahedral A and octahedral B sites via oxygen ions were analysed using the maximum entropy method (MEM). A precise 3D and 2D visualisation of the tetrahedral A and octahedral B sites gives the electronic isosurface shape, size, and bonding behaviour for all the compositions. Maximum A-O covalent bonding and maximum B-O ionic bonding favours an increase in coercivity. The magnetic hysteresis analysis (VSM) reveals a slow switching from paramagnetic to superparamagnetic behaviour with increased Co2+ content. The maximum magnetisation and coercivity in this present work are double the value compared to the reported values.
M. Charles Robert, M. Thavarani, N. Pavithra, S. Balaji Prasath, R. Saravanan, and Y. B. Kannan
Journal of Superconductivity and Novel Magnetism, ISSN: 15571939, eISSN: 15571947, Published: 2022 Springer Science and Business Media LLC
S.V. Meenakshi, R. Saravanan, N. Srinivasan, D. Dhayanithi, and Nambi Venkatesan Giridharan
Journal of Alloys and Compounds, ISSN: 09258388, Volume: 888, Published: 25 December 2021 Elsevier BV
Jegannathan Mangaiyarkkarasi and Ramachandran Saravanan
Rare Metals, ISSN: 10010521, eISSN: 18677185, Published: December 2021 Springer Science and Business Media LLC
Ferroelectric lead-free BaTi1−xZrxO3 ceramic powder samples with various compositions (x = 0, 0.04, 0.06) have been synthesized by conventional high-temperature solid-state reaction method at 1450 °C for 10 h. Influences of Zr doping on the inter-atomic bonding and charge density distributions inside the lattice structure of BaTiO3 were analyzed through powder X-ray diffraction (XRD) and maximum entropy method. Lattice parameter and cell volume values are found to be increasing with the incorporation of Zr content. Calculated average grain sizes are found to be in the range of 23–28 nm. Maximum entropy mapping of electron density analysis reveals the reduction in ionic nature along Ba–O bond and the enhancement of covalent nature along Ti–O bond. Energy band gap values were determined from ultraviolet–visible (UV–Vis) spectra. Surface morphology and microstructures of the samples were analyzed from scanning electron microscopy (SEM) micrographs. Particles with irregular sizes were observed in all the prepared ceramics. Stoichiometry of the samples was further confirmed by energy-dispersive X-ray spectroscopy (EDAX).
G. Gowri, R. Saravanan, N. Srinivasan, K. Karunya, P. Jeyasheela, and M. Uthra
Chemical Papers, ISSN: 03666352, eISSN: 13369075, Pages: 4337-4353, Published: August 2021 Springer Science and Business Media LLC
Aluminum-substituted LaFeO3 (La1−xAlxFeO3) (x = 0.05, 0.15, and 0.25) bulk multiferroics were synthesized by standard high temperature (1300 °C) solid-state reaction method. X-ray diffraction results confirmed that the prepared La1−xAlxFeO3 crystallizes in the orthorhombic phase. The 3D charge density distributions and arrangement of charges on 2D crystallographic planes and 1D charge density profiles between nearest neighboring atoms in the unit cell of La1−xAlxFeO3 have examined using the maximum entropy method. Deagglomerated particles having different shapes with irregular boundaries and size in the micrometer range has observed through scanning electron microscopy micrographs. The increase in the substitution of Al in LaFeO3 enhances the magnetic and electrical properties of the host system. Magnetic measurements revealed that Al substitution in LaFeO3 leads to ferromagnetic ordering with the enhanced coercive field, between 1044 G (x = 0.05) and 3031 G (x = 0.25). The dielectric constant of the synthesized samples lies in the range of 213 to 771. ferroelectric measurements demonstrate elliptical P–E loops with high remanent polarization (Pr) for all the samples. The optical measurements show that the Al substitution in LaFeO3 leads to the decrease in the energy band gap (Eg). The structural and charge-related magnetoelectric properties have been investigated through charge density values and spin.
G. Gowri, R. Saravanan, N. Srinivasan, O.V. Saravanan, and S. Sonai
Materials Chemistry and Physics, ISSN: 02540584, Volume: 267, Published: 15 July 2021 Elsevier BV
Abstract A series of Zn-substituted La1−xZnxFeO3 (x = 0.00, 0.05, 0.15, and 0.25) bulk ceramics was prepared using solid-state reaction method. The XRD patterns and profile refinements confirm the orthorhombic phase formation in La1−xZnxFeO3. The charge density distribution in the La1−xZnxFeO3 unit cells were analyzed qualitatively and quantitatively. The average particle size and energy band gap were determined using the SEM images and UV–Visible absorption spectra. The magnetic hysteresis (M − H) curves show weak ferromagnetic order and shift in the hysteresis curves. The Zn-substituted system (x = 0.25), exhibits relatively high dielectric constant with low dielectric loss. Ferroelectric measurements show the rectangular-like P-E loops with Barkhausen jumps. In this work, the effect of Zn-substitution on the crystal lattice and hence the modified optical, and multiferroic properties of LaFeO3 have been examined through charge density analysis which has not been investigated so far.
S. V. Meenakshi, R. Saravanan, N. Srinivasan, O. V. Saravanan, D. Dhayanithi, and Nambi Venkatesan Giridharan
Journal of Electronic Materials, ISSN: 03615235, eISSN: 1543186X, Pages: 400-401, Published: January 2021 Springer Science and Business Media LLC
In the original article
S. V. Meenakshi, R. Saravanan, N. Srinivasan, O. V. Saravanan, D. Dhayanithi, and Nambi Venkatesan Giridharan
Journal of Electronic Materials, ISSN: 03615235, eISSN: 1543186X, Pages: 7349-7362, Published: December 2020 Springer Science and Business Media LLC
Particulate ceramic-composite (1 − x) BaTiO3 + x NiFe2O4 with compositions (x = 0.2, 0.4, 0.6, and 0.8) was prepared by solid-state synthesis. The presence of two phases (spinel and tetragonal) in the hybrid composite was confirmed by the XRD. Quantitative phase analysis with structural refinement was carried out using a profile refinement method. The variation of the capacitance with frequency was studied and for x = 0.6, the graph shows a maximum capacitance of 258 pF at 100 Hz. The saturation magnetization (Ms) calculated from the magnetic hysteresis measurement increased with increase in the ferrite content and reached a maximum of 23.282 emu/g for x = 0.8. The material’s microstructure particle sizes varied from 1.74 μm to 3.27 μm as shown by SEM micrographs. Electron density analysis was used to study the bonding between the atoms of the composite (1 − x) BaTiO3 + x NiFe2O4 with compositions (x = 0.2, 0.4, 0.6, and 0.8). This is a new approach to studying the electron distribution and bonding nature of the samples. The analysis confirmed that the bonds of the individual atoms were responsible for the electric and the magnetic properties of the prepared ceramic composite.
Ujjal Chowdhury, Sudipta Goswami, Amritendu Roy, Shailendra Rajput, A. K. Mall, R. Gupta, S. D. Kaushik, V. Siruguri, S. Saravanakumar, S. Israel, R. Saravanan, A. Senyshyn, T. Chatterji, J. F. Scott, Ashish Garg, and Dipten Bhattacharya
Physical Review B, ISSN: 24699950, eISSN: 24699969, Volume: 100, Published: 12 November 2019 American Physical Society (APS)
In this Letter, we demonstrate that a small but finite ferroelectric polarization in orthorhombic LuFeO$_3$ is primarily of electronic origin (oriented along a-axis) driven by commensurate (k = 0) and collinear magnetic structure. The nonpolar orthorhombic lattice (space group $Pnma$) undergoes isostructural transition at the magnetic transition temperature $T_N$ ($\\sim$600 K). Application of electric field, however, induces finite piezostriction via electrostriction resulting in clear domain contrast images in piezoresponse force microscopy.
V. Shanmugavalli, O. V. Saravanan, K. Vishista, and R. Saravanan
Ionics, ISSN: 09477047, eISSN: 18620760, Pages: 4393-4408, Published: 1 September 2019 Springer Science and Business Media LLC
Solution combustion method was used to synthesize ZnCo2O4 nanoparticles. Then, physical blending method was used to prepare ZnCo2O4/polyaniline (PANI) composite. The crystallite sizes of the ZnCo2O4 and ZnCo2O4/PANI composites prepared were 17.16 nm and 25.46 nm, respectively, as calculated by XRD studies. The density of nanoparticles, cell parameters, and unit cell volume were calculated by Rietveld refinement technique. The cell volume and lattice constant obtained from the Rietveld method were in good agreement with those of Scherer’s method. Functional groups of the samples were further studied using FTIR. Maximum entropy method (MEM) was employed to study the chemical bonding and electron density distribution of the nanoparticles. The electrochemical properties of the pure and composite materials varied due to the changes in the electron density distribution and chemical bonding. The W–H method and size–strain plot method were used to determine the crystallite size and strain. The results obtained through these methods were in accordance with those of Scherer’s method. The morphological observations made through SEM revealed that the change in morphology of the nanomaterial has enhanced the electrochemical properties of the composite. The shape and size of the pure and nanocomposite observed by SEM and XRD were further confirmed by HR-TEM images. Selected area electron diffraction pattern of HR-TEM images was used to further confirm the crystalline nature of ZnCo2O4 and ZnCo2O4/PANI nanoparticles as examined by XRD. The CV and chronopotentiometry studies were used to study the electrochemical behavior of the samples. The specific capacitance values of pure and composite as obtained from CV study were 711 F/g and 867 F/g, respectively, at the applied current density of 0.5 A/g. Good capacitance retention of 98.9% was achieved for the nanocomposite up to 1000 cycles at a high current density of 4 A/g. The investigation by electrochemical impedance spectrum study also revealed that the nanocomposite exhibited low resistance compared with that of pure. The symmetrical capacitor was assembled by fabricating it with ZnCo2O4/PANI as the electrodes. The high specific capacitance and enhanced efficiency have been achieved due to the presence of PANI in the nanocomposite.
S. Sasikumar, S. Saravanakumar, S. Asath Bahadur, and R. Saravanan
Applied Physics A: Materials Science and Processing, ISSN: 09478396, eISSN: 14320630, Volume: 125, Published: 1 July 2019 Springer Science and Business Media LLC
Abstract(1 − x)(Na0.97K0.03)NbO3–xBaTiO3 ceramics [NKN–xBT, (x = 0.1, 0.2)] were synthesized by solid-state sintering process. The powder X-ray diffraction results showed that the crystalline symmetry of the sintered samples was transformed from tetragonal (x = 0.1) to cubic (x = 0.2) symmetry. Morphological properties of NKN–xBT (x = 0.1, 0.2) were investigated by scanning electron microscopic images. Energy band gap was studied by UV–visible spectroscopy, which is found to decrease with the addition of Ba2+ content in the host lattice. Ferroelectric behavior of the samples was examined by polarization versus electric field hysteresis loop measurements, which is found that the tetragonal phase exhibits enhanced properties. The values of remnant polarization, maximum polarization and coercive field for x = 0.1 is found to be 12.25 μC/cm2, 14.38 μC/cm2 and 6.56 kV/cm, respectively. Based on the previous reports modified NKN–xBT (x = 0.1, 0.2) ceramics considered as promising lead-free candidates for ferroelectric and dielectric components.
G. Gowri, R. Saravanan, S. Sasikumar, M. Nandhakumar, and R. Ragasudha
Journal of Materials Science: Materials in Electronics, ISSN: 09574522, eISSN: 1573482X, Pages: 4409-4426, Published: 1 March 2019 Springer Science and Business Media LLC
Strontium (Sr) substituted LaFeO3 (La1−xSrxFeO3) (x = 0.05, 0.10, 0.15 and 0.20) multiferroics were synthesized by the conventional high temperature solid-state reaction method. The X-ray diffraction was used to analyze the phase formation and purity of La1−xSrxFeO3 multiferroics. The X-ray diffraction patterns confirm that all the samples are monophasic with orthorhombic structure. The charge density distribution and the interatomic chemical bonding between the neighbouring atoms in the unit cell were examined using the structure factors obtained through the refinement process. SEM micrographs were used to observe the surface morphology and to determine the average particle size. UV–Vis spectrographs and magnetic hysteresis (M–H) loops from magnetic measurements were exploited to investigate the optical and magnetic behavior of the samples. The magnetic hysteresis loops indicate that the prepared La1−xSrxFeO3 multiferroics exhibit ferromagnetic behavior. Ferromagnetism was observed to be relatively prominent for x = 0.05 sample, with high values of magnetic parameters such as Ms, Mr, and HC as 2.4 emu/g, 1.12 emu/g, and 1616 G respectively. The dielectric measurements indicate that the sample with Sr content x = 0.05, attains the giant value of dielectric constant of about 2.3 × 105 and ac conductivity of about 0.2 Ω−1m−1 when compared to the other samples. The optical, magnetic and dielectric properties of La1−xSrxFeO3 multiferroics have been examined and also have been correlated with the charge, bonding nature and the spin of the constituent ions which has not been explored in open literature so far.
D. Sivaganesh, S. Saravanakumar, V. Sivakumar, K. S. Syed Ali, Esther Akapo, Ezra Alemayehu, R. Rajajeyaganthan, and R. Saravanan
Journal of Materials Science: Materials in Electronics, ISSN: 09574522, eISSN: 1573482X, Pages: 2966-2974, Published: 15 February 2019 Springer Science and Business Media LLC
The hexagonal structured Zn1−xAlxO (x = 0.00, 0.04, 0.06, 0.08 and 0.10) materials was synthesized by co-precipitation method. Structural, morphological and photoluminescence properties of Al doped ZnO powders were investigated by powder X-ray diffraction, scanning electron microscopy and photoluminescence characterizations, respectively. Structural analysis was done by Rietveld refinement technique. The spherical shaped morphology was observed in ZnO:Al powders. The bonding features were analyzed by using electron density distribution studies and the photoluminescence properties of Zn1−xAlxO (x = 0.00, 0.04, 0.06, 0.08 and 0.10) was also revealed.
S. Saravanakumar, D. Sivaganesh, K.S. Syed Ali, M. Charles Robert, M. Prema Rani, R. Chokkalingam, and R. Saravanan
Physica B: Condensed Matter, ISSN: 09214526, Volume: 545, Pages: 134-140, Published: 15 September 2018 Elsevier BV
Abstract The phasepure nanostructures of Zn1-xMnxS (x = 0.0, 0.04, 0.06 and 0.08) has been synthesized by using chemical precipitation method. The prepared nanostructures are characterized by powder X-ray diffraction (PXRD) method. The structural properties are analyzed through Rietveld refinement analysis. The charge density distribution studies are also done using maximum entropy method (MEM). The bonding features have been analyzed using MEM method. The morphological studies are done using Scanning Electron Microscopy (SEM) and it confirms that the prepared systems are in nano range. The optical characterization has also been done through UV spectrophotometer.
S. Sasikumar, R. Saravanan, S. Saravanakumar, and M. Charles Robert
Applied Physics A: Materials Science and Processing, ISSN: 09478396, eISSN: 14320630, Volume: 124, Published: 1 January 2018 Springer Science and Business Media LLC
Polycrystalline lead-free (1 − x)(K0.5Bi0.5)TiO3-xBaTiO3, ((1 − x)KBT-xBT) (x = 0.00, 0.08, 0.12) ceramics were synthesized via solid-state reaction method. The powder X-ray diffraction (PXRD) and structural refinement results confirm that a single-phase tetragonal structure with space group P4mm. Charge density distribution inside the unit cell of (1 − x)KBT-xBT was investigated by the maximum entropy method. Charge density analysis reveals the reduction in ionic nature along K/Bi–O bond and enhancement of covalent nature along Ti–O bond with the addition of BaTiO3. The charge density distribution studies done using maximum entropy method for (1 − x)KBT-xBT have not been done so far. The surface morphology study was done using scanning electron microscopy (SEM). Energy dispersive X-rays spectra (EDS) were used to investigate the elemental compositions present in the system. The dielectric constant and loss tangent were studied as a function of frequency. The dielectric constant and loss were decreased with increase of frequency. Room temperature dielectric constant (ɛ) and loss (tan δ) were measured for x = 0.00 about 511 and 0.51, respectively, at a frequency of 10 kHz.
S. Sasikumar, R. Saravanan, and S. Saravanakumar
Journal of Materials Science: Materials in Electronics, ISSN: 09574522, eISSN: 1573482X, Pages: 1198-1208, Published: 1 January 2018 Springer Science and Business Media LLC
The lead-free (1 − x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3, (x = 0.4, 0.5 and 0.6) (abbreviated as (1 − x)BZT–xBCT) ceramics were prepared by solid-state reaction method. X-ray diffraction (XRD) study revealed the perovskite phase of the prepared ceramics at room temperature (RT) for all compositions. The XRD powder profile refinement analysis showed no extra phases and the calculated peak intensities matched well with the observed ones. The charge density distribution studies revealed the chemical bonding nature, qualitative and quantitative features of the distributions of the electrons contributed by the dopant atoms in the unit cell. Scanning electron microscopy images revealed the uniform distribution of powder grains. The elemental compositions of the samples were analyzed by energy dispersive X-ray spectrometer. The optical band gap for all the samples has been estimated to be between 3.15 and 3.07 eV. Enhanced piezoelectric constant, d33 = 276 pC/N was obtained for x = 0.5 composition in the morphotropic phase boundary (MPB).
Natarajan Thenmozhi and Ramachandran Saravanan
Rare Metals, ISSN: 10010521, eISSN: 18677185, Pages: 1-11, Published: 10 October 2017 Springer Science and Business Media LLC
Doped lanthanum manganites La1−xCaxMnO3 with five different concentrations of Ca (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by high-temperature solid-state reaction method and characterized. The prepared samples were experimentally analyzed by X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and vibrating sample magnetometer (VSM) measurements. Orthorhombic structure is confirmed for this compound from powder X-ray diffraction data. The XRD data confirm the shrinkage in the unit cell of synthesized samples for increasing calcium concentration. The UV–Visible analysis for the estimation of optical band gap (Eg) reveals that the band gap decreases with the incorporation of Ca. The synthesized samples were investigated for charge density distribution using maximum entropy method, utilizing the XRD data sets. From the charge density analysis, it is found that the bond lengths for La–O and Mn–O bonds decrease with the addition of Ca. The ionic nature between La and O atoms and covalent nature between Mn and O atoms are enhanced for 40% of calcium-doping. For 50% of Ca-doped sample, ionic nature between La and O atoms and covalent nature between Mn and O atoms decrease. All the prepared samples exhibit ferromagnetism at 20 K and paramagnetism at 300 K.
Y. B. Kannan, R. Saravanan, N. Srinivasan, and I. Ismail
Journal of the Australian Ceramic Society, ISSN: 0004881X, Pages: 577-581, Published: 1 October 2017 Springer Science and Business Media LLC
The dielectric properties such as dielectric constant both real and imaginary part, dielectric loss factor, and AC resistivity have been studied in this work on mechanically alloyed Ni0.5Zn0.5Fe2O4 nano ferrite particles sintered from 700 to 1200 °C as a function of frequency in the range of 0.1 Hz to 15 MHz. The dielectric constant (ε′) decreases with increase in sintering temperature and the decrease is explained with proper mechanism. The samples sintered at 900 and 1200 °C show slightly high ε′ value compared to their predecessor. The AC resistivity at room temperature is found to be of the order of 109 Ω-cm.
Y. B. Kannan, R. Saravanan, N. Srinivasan, K. Praveena, and K. Sadhana
Journal of Superconductivity and Novel Magnetism, ISSN: 15571939, eISSN: 15571947, Pages: 2673-2682, Published: 1 September 2017 Springer Science and Business Media LLC
Cobalt and manganese-substituted zinc ferrite X0.4Zn0.6Fe2O4 (X = Co, Mn) nanoparticles have been synthesized by co-precipitation method and characterized for structural, morphology, and magnetic properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). The Rietveld refinement method is employed to refine the XRD powder data, and the structural parameters are calculated from the refinement. Substitution of cobalt and manganese causes the lattice parameter to decrease. Particle size, measured from XRD, lies in the nanometer regime. A low saturation magnetization value is obtained in both samples, and the presence of non-collinear spin arrangement is found at octahedral sites. The maximum entropy method (MEM) is employed to study the strength of the bond between the atoms at tetrahedral and octahedral sites in the unit cell of ferrites. Optical band gap energy of the samples is determined by using UV–VIS techniques.
S. Sasikumar, R. Saravanan, S. Saravanakumar, and K. Aravinth
Journal of Materials Science: Materials in Electronics, ISSN: 09574522, eISSN: 1573482X, Pages: 9950-9963, Published: 1 July 2017 Springer Science and Business Media LLC
Single phased lead-free (1 − x)(Na0.5Bi0.5)TiO3–xBaTiO3 (x = 0.00, 0.04, 0.08 and 0.12) ((1 − x)NBT–xBT) ceramics were synthesized by the solid-state reaction method. The powder X-ray diffraction patterns and profile refinements revealed that, for 0.04 < x < 0.08, the prepared ceramics have been crystallized in morphotropic phase boundary between rhombohedral to tetragonal structures. The charge distribution and bonding behaviour in (1 − x)NBT–xBT unit cell were completely analyzed through charge density distribution studies. UV–visible analysis reveals that, the optical band gap energy of the solid solution increases with addition of BaTiO3 content. The surface morphology and elemental compositions for the sintered powders were analyzed through scanning electron microscopy and energy dispersive X-ray studies. Electrical measurements on the solid solutions showed that the maximum values of the dielectric constant, the remnant polarization and the piezoelectric coefficient are reached at near (x = 0.08) the morphotropic phase boundary (ε = 4070 at 100 kHz; Pr = 18.92 µC/cm2; d33 = 122 pC/N). Thus, the (1 − x)NBT–xBT system is expected to be a promising candidate for lead-free piezoelectric material.
S. Sasikumar and R. Saravanan
Journal of Electronic Materials, ISSN: 03615235, Pages: 4187-4196, Published: 1 July 2017 Springer Science and Business Media LLC
Abstract(1 − x)(Na1−yKy)NbO3-xBaTiO3 (abbreviated as NKN-BT, x = 0.1, 0.2; y = 0.01, 0.05) ceramics were synthesized by the solid-state reaction method. Powder x-ray diffraction analysis in combination with the profile refinement method was employed for quantitative phase analysis and structural refinement. The x-ray diffraction study shows that phase transition occurs from tetragonal to distorted cubic with the compositions between x = 0.1 and x = 0.2. The spatial arrangements of the electron distribution and bonding nature of the samples have been analyzed through the maximum entropy method. The optical band gap energy of the prepared solid solutions has been determined using UV-visible spectrophotometry. The optical band gap energy of the solid solutions decreases with the increase in BaTiO3 content. The elemental composition of these ceramics has been studied using energy dispersive x-ray analysis and the microstructure has been examined by scanning electron microscopy. The piezoelectric coefficient (d33) measurement of the ceramics shows the enhancement of piezoelectric properties in the tetragonal phase. The maximum value of the piezoelectric coefficient (d33) obtained for the solid solution is 120 pC/N. With increasing BaTiO3 content in the solid solutions, the ferroelectric behavior weakens.
Jegannathan Mangaiyarkkarasi, Subramanian Sasikumar, Olai Vasu Saravanan, and Ramachandran Saravanan
Frontiers of Materials Science, ISSN: 2095025X, eISSN: 20950268, Pages: 182-189, Published: 1 June 2017 Springer Science and Business Media LLC
An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1−xSrxZr0.1Ti0.9O3 (short for BSZT, x = 0, 0.05, 0.07 and 0.14) ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method (MEM). Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiO3 structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.
S. Sasikumar, R. Saravanan, and K. Aravinth
Physica B: Condensed Matter, ISSN: 09214526, Volume: 512, Pages: 58-67, Published: 1 May 2017 Elsevier BV
Abstract The solid solutions of lead-free (1- x )(Na 1- y K y )(Nb 1- z Sb z )O 3 - x BaTiO 3 (with x =0.1, 0.2; y =0.03, 0.05; z =0.05, 0.1) (abbreviated as (1- x )NKNS- x BT) ceramics have been synthesized using conventional solid-state reaction method. The results of X-ray diffraction analysis show that all the grown specimens of NKNS display typical perovskite structure. With BaTiO 3 (BT) addition, a structural phase transition from tetragonal to cubic structure has been observed. The structural parameters of (1- x )NKNS- x BT powders were determined by profile refinements based on the analysis of X-ray powder diffraction. The charge density distributions of the prepared samples have been investigated by observed structure factors to understand the chemical bonding nature of (1- x )NKNS- x BT powders. The optical absorption of the ceramics has been investigated using UV–visible spectrophotometer. Scanning electron microscopic (SEM) measurements were performed to study the surface morphology of the prepared solid solutions. The elemental compositions of the (1- x )NKNS- x BT samples were analyzed by energy-dispersive X-ray (EDS) spectrometer. The dielectric constant versus temperature plots of the solid solutions exhibit ferroelectric to paraelectric phase transition, which is dependent on the BaTiO 3 content. The ferroelectric nature of the samples has been determined through polarization and electric field hysteresis measurements.
Research Projects By Dr. R. Saravanan
1. NRB (DRDO)
Preparation, Characterization And Local Structure Of New Lead Free Piezo Ceramics
Funded By DRDO(Naval Research Board Of DRDO, Govt. Of India)
Duration - 3 Years-Completed
Oxide Based Dilute Magnetic Materials – Synthesis And Local Structural Characterization
Funded ByUGC (University Grants Commission, India)
Duration - 3 Years-Completed
Bulk Growth And X-Ray Characterization Of Local Structure In Silicon And Germanium Based Dilute Magnetic Semiconductors
Funded By CSIR(Council Of Scientific And Industrial Research, India)
Duration - 3 Years-Completed
Thermal Motion Of Core And Valence Electrons, Charge Transfer And MEM [Maximum Entropy Method] Electron Density Distributions In Technologically Important Semiconductors.
Funded By CSIR (Council Of Scientific And Industrial Research, India)
Duration - 3 Years-Completed
Asf88win (Other Info)
IUCr reference; https://www.iucr.org/resources/other-directories/software/asf88win
IUCr reference; https://www.iucr.org/resources/other-directories/software/dataredwin
IUCr reference; https://www.iucr.org/resources/other-directories/software/dremablpwin
IUCr reference https://www.iucr.org/resources/other-directories/software/reducewin
IUCr reference; https://www.iucr.org/resources/other-directories/software/scatt771win
IUCr reference; https://www.iucr.org/resources/other-directories/software/sfac331
IUCr reference; https://www.iucr.org/resources/other-directories/software/sfac332
IUCr reference; https://www.iucr.org/resources/other-directories/software/sfac333
IUCr reference; https://www.iucr.org/resources/other-directories/software/sfac335
IUCr reference; https://www.iucr.org/resources/other-directories/software/grain
IUCr reference; https://www.iucr.org/resources/other-directories/software/fcc
BCC (Similar to FCC)
IUCr reference; https://www.iucr.org/resources/other-directories/software/bcc
KCl ((Similar to NaCl)
IUCr reference; https://www.iucr.org/resources/other-directories/software/kcl
Diamond (For diamond structures)
IUCr reference; https://www.iucr.org/resources/other-directories/software/diamond2
He has contributed to the teaching community by delivering a software program for the consolidation and maintenanc