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Papers by Manimuthu Periyasamy
Transactions of the Indian Institute of Metals, 2011
Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis ... more Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to
Solid State Sciences, 2011
CrO2 requires non-ambient conditions to stabilize Cr in 4+ state. Usually it is prepared by the h... more CrO2 requires non-ambient conditions to stabilize Cr in 4+ state. Usually it is prepared by the hydrothermal method which requires high pressure and super criticality of water. For more than a sesqui century there are no reports on the preparation CrO2 by a simple single step rapid synthesis method at ambient condition. The self ignition exothermic combustion reaction between CrO3
Physica B: Condensed Matter, 2014
ceramics (LFO) with garnet structure were prepared by solid-state reaction method and a part of t... more ceramics (LFO) with garnet structure were prepared by solid-state reaction method and a part of the sample was ball milled for 15 h (LFO15h) using a high energy ball mill to study the grain size effect. The cubic garnet phase was confirmed for both LFO and LFO15h samples by X-ray diffraction analysis. The magnetic behavior was studied using a Vibrating Sample Magnetometer and it shows a clear hysteresis loop with ferrimagnetic ordering at room temperature for both LFO and LFO15h samples. X-ray photoelectron spectra reveal the presence of single valence state of Fe ions (Fe 3 þ) in the unmilled sample and mixed valence state of Fe ions (i.e., Fe 2 þ and Fe 3 þ) in the 15 h ball milled sample. Magneto-dielectric (MD) studies that have been carried out using an indigenous magneto-impedance setup show large MD coupling at room temperature for the LFO15 h in comparison to the LFO sample, making it a candidate explorable for applications in magneto dielectric devices.
Applied Surface Science, 2011
The effect of Li (0-5 wt%) doping on the properties of WO 3 thin films deposited using an automat... more The effect of Li (0-5 wt%) doping on the properties of WO 3 thin films deposited using an automated homemade spray pyrolysis unit is studied. Change in structural and optical properties is observed on doping with Li. The XRD patterns shows that undoped WO 3 film has an orthorhombic phase while the Li (1-5 wt%) doped WO 3 films have tetragonal phase. The SEM and AFM images confirm relatively smooth surface of Li doped WO 3 films compared to undoped WO 3 film. Transmission spectra reveal that the transparency of the Li-doped films is much greater than that of undoped film. From the transmission data, the direct, indirect bandgap and phonon energies were calculated. Room temperature photoluminescence spectra showed pronounced blue emission on doping with Li.
Applied Surface Science, 2013
Undoped and lithium (Li) (1-5 wt%) doped MoO 3 thin films were deposited over ITO coated glass su... more Undoped and lithium (Li) (1-5 wt%) doped MoO 3 thin films were deposited over ITO coated glass substrates by spray pyrolysis at a substrate temperature of 325 ˚C. Undoped film was oriented along the <0k0> direction. The texture coefficient value of the undoped film was higher for the (020) plane compared to other planes of undoped and 'Li' doped films. The 100% peak (021) plane of orthorhombic MoO 3 and hexagonal phase were induced upon doping with 'Li'. The crystallite size of the undoped film is less compared to the 'Li' doped films. The intense Raman peak at 996 cm-1 is due to the terminal oxygen (Mo 6+ =O stretching mode) in the orthorhombic α-MoO 3 phase. The characteristic Mo 3d 5/2 and 3d 3/2 doublet caused by spin-orbit coupling are clearly resolved with a splitting of 3.1 eV in the XPS spectra. Scanning electron microscope (SEM) image shows a change in the microstructure, consistent with the change from α-MoO 3 to mixed α and hexagonal phases. Sprout like features were observed in SEM image and rod like features in atomic force microscope (AFM) images. Both direct and indirect band gap showed red shift upon doping with 'Li' compared to undoped film as estimated from the transmittance spectra. Intensity of the green photoluminescence (PL) emission spectra was found to quench with 'Li' concentration.
Applied Physics A, 2014
ABSTRACT
Journal of Physics D: Applied Physics, 2011
ABSTRACT Perovskite SrFeO3−δ belongs to the Ruddlesden–Popper class of system exhibiting interest... more ABSTRACT Perovskite SrFeO3−δ belongs to the Ruddlesden–Popper class of system exhibiting interesting electronic and magnetic properties. Nanocrystalline SrFeO3−δ synthesized successfully by the thermal decomposition method has the cubic phase as confirmed from x-ray diffraction. The non-stoichiometric nature is confirmed from the selected area electron diffraction pattern. Oxygen stoichiometry, which plays an important role in determining the physical properties, was found to be 2.91 from the iodometric titration. Mössbauer measurement reveals paramagnetic behaviour and suggests mixed valence state of Fe. Relaxor type ferroelectricity is evident from the dielectric plots, which is also reflected in the thermal study. Relaxor ferroelectric behaviour is reported for the first time in SrFeO2.91, arising due to mixed valency of Fe ion.
AIP Conference Proceedings, 2011
MoO3 thin films were deposited at 325 °C on ITO coated glass substrates by spray pyrolysis. The f... more MoO3 thin films were deposited at 325 °C on ITO coated glass substrates by spray pyrolysis. The film was more textured along (102) plane. The bandgaps were estimated (Tauc relation) from absorption coefficient and film thickness (405 nm). The film had a reticulated fibrous surface morphology with 25 to 35% transparency. Photoluminescence (PL) emission is also observed. Cyclic voltametric measurement was also performed. The efficiency of the dye sensitized solar cell (DSSC) fabricated using the MoO3 film as a counter electrode is measured from the I-V curve. The results are discussed.
Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpile... more Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpiles of unique optical and microwave devices that will also avoid complex geometries. We report the observation of temperature dependent negative dielectric constant (NDC) above 503 K in the perovskite PrMnO3, confirmed through impedance spectroscopy, obeying classical Drude theory. The principle behind the associated negative dielectric loss is explained using the Axelrod mechanism.
Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal to insulator transitio... more Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal to insulator transition (MIT) at 600 K, due to the empty 3d orbitals of Ti4+ along with the interactions of O2- and Tb3+ ions. Electric modulus plot, Nyquist plot and variations in relaxation time confirm the transition which is of second order. A broad change in magnetic moment, evident from the first-order derivative graph of M vs T without any magnetic phase transition is a behaviour typical in this family of compounds. Heat capacity measurements and their mechanism were discussed which supports MIT observed in Tb2Ti2O7, a phenomenon which is seldom observed in an empty d orbital pyrochlores.
Iron based compounds have drawn much attention for their potential as counter electrode in Li-ion... more Iron based compounds have drawn much attention for their potential as counter electrode in Li-ion batteries because of their low cost and low toxicity. Nanocrystalline transition metal CuFe2O4 thin film was deposited using an automated homemade spray pyrolysis unit over Antimony doped Tin Oxide (ATO) substrate. The ATO layer was deposited over the quartz substrate prior to deposition of ferrite film. X-ray diffraction (XRD) measurement shows that the film is of single phase, with tetragonal structure for CuFe2O4. Magnetization studies reveal that the film is ferrimagnetic in nature. Electrochemical measurement indicates porous CuFe2O4 film as promising electrodes for Li-ion batteries.
arXiv: Materials Science, 2018
Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpile... more Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpiles of unique optical and microwave devices that will also avoid complex geometries. We report the observation of temperature dependent negative dielectric constant in the perovskite PrMnO3 obeying the classical Drude theory and with an associated capacitive-inductive transition confirmed from impedance analysis.
Tb2Ti2O7: The cubic pyrochlore Quantum spin liquid reveals a sharp metal like to semiconductor tr... more Tb2Ti2O7: The cubic pyrochlore Quantum spin liquid reveals a sharp metal like to semiconductor transition (MIT) at 600 K, due to the empty 3d orbitals of Ti along with the interactions of O and Tb ions. Electric modulus plot, Nyquist plot and variations in relaxation time confirm the transition which is of second order. A broad change in magnetic moment, evident from the first-order derivative graph of M vs T without any magnetic phase transition is a behaviour typical in this family of compounds. Heat capacity measurements and their mechanism were discussed which supports MIT observed in Tb2Ti2O7, a phenomenon which is seldom observed in an empty d orbital pyrochlores. Metal Insulator Transition in vacant 3d orbital Quantum Spin Liquid: Tb2Ti2O7
Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal like to semiconductor ... more Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal like to semiconductor transition (MIT) at 600 K, due to the empty 3d orbitals of Ti4+ along with the interactions of O2- and Tb3+ ions. Electric modulus plot, Nyquist plot and variations in relaxation time confirm the transition which is of second order. A broad change in magnetic moment, evident from the first-order derivative graph of M vs T without any magnetic phase transition is a behaviour typical in this family of compounds. Heat capacity measurements and their mechanism were discussed which supports MIT observed in Tb2Ti2O7, a phenomenon which is seldom observed in an empty d orbital pyrochlores.
Lithium 5 wt% doped V2O5 thin film was deposited onto ITO substrate by spray pyrolysis technique.... more Lithium 5 wt% doped V2O5 thin film was deposited onto ITO substrate by spray pyrolysis technique. The substrate temperature was kept at 450 °C. 200 MeV Ag15+ ion beams at a fluence of 5×1012 ions/cm2 was irradiated on 5 wt% ‘Li’ doped V2O5 film of thickness 1367 nm. The XRD pattern confirms that the pristine film is non stoichiometry with orthorhombic structure and upon irradiation the crystallinity decreased and an obvious textured growth along (020) plane is induced. Raman peak observed at 917 cm−1 is due to oxygen deficiency. Upon irradiation, the optical transparency and band gap of the film decreased. Electrical transport property study shows that the resistivity increased by one order for the irradiated film.
ABSTRACT Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass sub... more ABSTRACT Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass substrate at 350 °C is irradiated with 100 MeV O7+ ion at a fluence of 5×1012 ions/cm2. X-ray diffraction shows that the pristine and irradiated films are polycrystalline with a tetragonal phase. Raman peaks suppressed upon irradiation imply large surface degradation which is also seen as a decrement in transparency in visible region to one half of the pristine film. Large red shift is observed in direct and indirect band gaps upon irradiation. Hall effect reveals slight increase in carrier concentration due to irradiation induced defects.
Applied Physics A, 2015
Abstract Perovskite SrFeO3−δ, a Ruddlesden–Popper class of system exhibits interesting electronic... more Abstract Perovskite SrFeO3−δ, a Ruddlesden–Popper class of system exhibits interesting electronic and magnetic properties. Influence of oxygen vacancies on the electrical response of nanocrystalline SrFeO2.91 as a function of temperature is investigated using impedance spectroscopy technique. A change observed in the Nyquist plot at 383 K has been analyzed in terms of localized and delocalized eg electrons. An unusual and interesting temperature-induced semiconductor to metal-like transition is observed in the frequency-dependent real part of dielectric permittivity. Dependence of frequency on the real and imaginary parts of impedance with respect to temperature supports the presence of semiconductor to metal-like transition in SrFeO2.91.
Transactions of the Indian Institute of Metals, 2011
Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis ... more Nb2O5 thin film electrodes have been deposited on indium tin oxide substrates by spray pyrolysis technique. XRD analysis reveals tetragonal phase of the film. Reticulated micro-fibrous surface morphology has been observed by scanning electron microscopy and atomic force microscopy indicates closely packed crystallites. Film thickness found using a stylus profilometer is around 26 nm. Transmittance spectra show the film to
Solid State Sciences, 2011
CrO2 requires non-ambient conditions to stabilize Cr in 4+ state. Usually it is prepared by the h... more CrO2 requires non-ambient conditions to stabilize Cr in 4+ state. Usually it is prepared by the hydrothermal method which requires high pressure and super criticality of water. For more than a sesqui century there are no reports on the preparation CrO2 by a simple single step rapid synthesis method at ambient condition. The self ignition exothermic combustion reaction between CrO3
Physica B: Condensed Matter, 2014
ceramics (LFO) with garnet structure were prepared by solid-state reaction method and a part of t... more ceramics (LFO) with garnet structure were prepared by solid-state reaction method and a part of the sample was ball milled for 15 h (LFO15h) using a high energy ball mill to study the grain size effect. The cubic garnet phase was confirmed for both LFO and LFO15h samples by X-ray diffraction analysis. The magnetic behavior was studied using a Vibrating Sample Magnetometer and it shows a clear hysteresis loop with ferrimagnetic ordering at room temperature for both LFO and LFO15h samples. X-ray photoelectron spectra reveal the presence of single valence state of Fe ions (Fe 3 þ) in the unmilled sample and mixed valence state of Fe ions (i.e., Fe 2 þ and Fe 3 þ) in the 15 h ball milled sample. Magneto-dielectric (MD) studies that have been carried out using an indigenous magneto-impedance setup show large MD coupling at room temperature for the LFO15 h in comparison to the LFO sample, making it a candidate explorable for applications in magneto dielectric devices.
Applied Surface Science, 2011
The effect of Li (0-5 wt%) doping on the properties of WO 3 thin films deposited using an automat... more The effect of Li (0-5 wt%) doping on the properties of WO 3 thin films deposited using an automated homemade spray pyrolysis unit is studied. Change in structural and optical properties is observed on doping with Li. The XRD patterns shows that undoped WO 3 film has an orthorhombic phase while the Li (1-5 wt%) doped WO 3 films have tetragonal phase. The SEM and AFM images confirm relatively smooth surface of Li doped WO 3 films compared to undoped WO 3 film. Transmission spectra reveal that the transparency of the Li-doped films is much greater than that of undoped film. From the transmission data, the direct, indirect bandgap and phonon energies were calculated. Room temperature photoluminescence spectra showed pronounced blue emission on doping with Li.
Applied Surface Science, 2013
Undoped and lithium (Li) (1-5 wt%) doped MoO 3 thin films were deposited over ITO coated glass su... more Undoped and lithium (Li) (1-5 wt%) doped MoO 3 thin films were deposited over ITO coated glass substrates by spray pyrolysis at a substrate temperature of 325 ˚C. Undoped film was oriented along the <0k0> direction. The texture coefficient value of the undoped film was higher for the (020) plane compared to other planes of undoped and 'Li' doped films. The 100% peak (021) plane of orthorhombic MoO 3 and hexagonal phase were induced upon doping with 'Li'. The crystallite size of the undoped film is less compared to the 'Li' doped films. The intense Raman peak at 996 cm-1 is due to the terminal oxygen (Mo 6+ =O stretching mode) in the orthorhombic α-MoO 3 phase. The characteristic Mo 3d 5/2 and 3d 3/2 doublet caused by spin-orbit coupling are clearly resolved with a splitting of 3.1 eV in the XPS spectra. Scanning electron microscope (SEM) image shows a change in the microstructure, consistent with the change from α-MoO 3 to mixed α and hexagonal phases. Sprout like features were observed in SEM image and rod like features in atomic force microscope (AFM) images. Both direct and indirect band gap showed red shift upon doping with 'Li' compared to undoped film as estimated from the transmittance spectra. Intensity of the green photoluminescence (PL) emission spectra was found to quench with 'Li' concentration.
Applied Physics A, 2014
ABSTRACT
Journal of Physics D: Applied Physics, 2011
ABSTRACT Perovskite SrFeO3−δ belongs to the Ruddlesden–Popper class of system exhibiting interest... more ABSTRACT Perovskite SrFeO3−δ belongs to the Ruddlesden–Popper class of system exhibiting interesting electronic and magnetic properties. Nanocrystalline SrFeO3−δ synthesized successfully by the thermal decomposition method has the cubic phase as confirmed from x-ray diffraction. The non-stoichiometric nature is confirmed from the selected area electron diffraction pattern. Oxygen stoichiometry, which plays an important role in determining the physical properties, was found to be 2.91 from the iodometric titration. Mössbauer measurement reveals paramagnetic behaviour and suggests mixed valence state of Fe. Relaxor type ferroelectricity is evident from the dielectric plots, which is also reflected in the thermal study. Relaxor ferroelectric behaviour is reported for the first time in SrFeO2.91, arising due to mixed valency of Fe ion.
AIP Conference Proceedings, 2011
MoO3 thin films were deposited at 325 °C on ITO coated glass substrates by spray pyrolysis. The f... more MoO3 thin films were deposited at 325 °C on ITO coated glass substrates by spray pyrolysis. The film was more textured along (102) plane. The bandgaps were estimated (Tauc relation) from absorption coefficient and film thickness (405 nm). The film had a reticulated fibrous surface morphology with 25 to 35% transparency. Photoluminescence (PL) emission is also observed. Cyclic voltametric measurement was also performed. The efficiency of the dye sensitized solar cell (DSSC) fabricated using the MoO3 film as a counter electrode is measured from the I-V curve. The results are discussed.
Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpile... more Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpiles of unique optical and microwave devices that will also avoid complex geometries. We report the observation of temperature dependent negative dielectric constant (NDC) above 503 K in the perovskite PrMnO3, confirmed through impedance spectroscopy, obeying classical Drude theory. The principle behind the associated negative dielectric loss is explained using the Axelrod mechanism.
Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal to insulator transitio... more Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal to insulator transition (MIT) at 600 K, due to the empty 3d orbitals of Ti4+ along with the interactions of O2- and Tb3+ ions. Electric modulus plot, Nyquist plot and variations in relaxation time confirm the transition which is of second order. A broad change in magnetic moment, evident from the first-order derivative graph of M vs T without any magnetic phase transition is a behaviour typical in this family of compounds. Heat capacity measurements and their mechanism were discussed which supports MIT observed in Tb2Ti2O7, a phenomenon which is seldom observed in an empty d orbital pyrochlores.
Iron based compounds have drawn much attention for their potential as counter electrode in Li-ion... more Iron based compounds have drawn much attention for their potential as counter electrode in Li-ion batteries because of their low cost and low toxicity. Nanocrystalline transition metal CuFe2O4 thin film was deposited using an automated homemade spray pyrolysis unit over Antimony doped Tin Oxide (ATO) substrate. The ATO layer was deposited over the quartz substrate prior to deposition of ferrite film. X-ray diffraction (XRD) measurement shows that the film is of single phase, with tetragonal structure for CuFe2O4. Magnetization studies reveal that the film is ferrimagnetic in nature. Electrochemical measurement indicates porous CuFe2O4 film as promising electrodes for Li-ion batteries.
arXiv: Materials Science, 2018
Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpile... more Negative dielectric constant materials, once an incumbrance for physicists, are now the stockpiles of unique optical and microwave devices that will also avoid complex geometries. We report the observation of temperature dependent negative dielectric constant in the perovskite PrMnO3 obeying the classical Drude theory and with an associated capacitive-inductive transition confirmed from impedance analysis.
Tb2Ti2O7: The cubic pyrochlore Quantum spin liquid reveals a sharp metal like to semiconductor tr... more Tb2Ti2O7: The cubic pyrochlore Quantum spin liquid reveals a sharp metal like to semiconductor transition (MIT) at 600 K, due to the empty 3d orbitals of Ti along with the interactions of O and Tb ions. Electric modulus plot, Nyquist plot and variations in relaxation time confirm the transition which is of second order. A broad change in magnetic moment, evident from the first-order derivative graph of M vs T without any magnetic phase transition is a behaviour typical in this family of compounds. Heat capacity measurements and their mechanism were discussed which supports MIT observed in Tb2Ti2O7, a phenomenon which is seldom observed in an empty d orbital pyrochlores. Metal Insulator Transition in vacant 3d orbital Quantum Spin Liquid: Tb2Ti2O7
Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal like to semiconductor ... more Tb2Ti2O7: The cubic pyrochlore - Quantum spin liquid reveals a sharp metal like to semiconductor transition (MIT) at 600 K, due to the empty 3d orbitals of Ti4+ along with the interactions of O2- and Tb3+ ions. Electric modulus plot, Nyquist plot and variations in relaxation time confirm the transition which is of second order. A broad change in magnetic moment, evident from the first-order derivative graph of M vs T without any magnetic phase transition is a behaviour typical in this family of compounds. Heat capacity measurements and their mechanism were discussed which supports MIT observed in Tb2Ti2O7, a phenomenon which is seldom observed in an empty d orbital pyrochlores.
Lithium 5 wt% doped V2O5 thin film was deposited onto ITO substrate by spray pyrolysis technique.... more Lithium 5 wt% doped V2O5 thin film was deposited onto ITO substrate by spray pyrolysis technique. The substrate temperature was kept at 450 °C. 200 MeV Ag15+ ion beams at a fluence of 5×1012 ions/cm2 was irradiated on 5 wt% ‘Li’ doped V2O5 film of thickness 1367 nm. The XRD pattern confirms that the pristine film is non stoichiometry with orthorhombic structure and upon irradiation the crystallinity decreased and an obvious textured growth along (020) plane is induced. Raman peak observed at 917 cm−1 is due to oxygen deficiency. Upon irradiation, the optical transparency and band gap of the film decreased. Electrical transport property study shows that the resistivity increased by one order for the irradiated film.
ABSTRACT Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass sub... more ABSTRACT Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass substrate at 350 °C is irradiated with 100 MeV O7+ ion at a fluence of 5×1012 ions/cm2. X-ray diffraction shows that the pristine and irradiated films are polycrystalline with a tetragonal phase. Raman peaks suppressed upon irradiation imply large surface degradation which is also seen as a decrement in transparency in visible region to one half of the pristine film. Large red shift is observed in direct and indirect band gaps upon irradiation. Hall effect reveals slight increase in carrier concentration due to irradiation induced defects.
Applied Physics A, 2015
Abstract Perovskite SrFeO3−δ, a Ruddlesden–Popper class of system exhibits interesting electronic... more Abstract Perovskite SrFeO3−δ, a Ruddlesden–Popper class of system exhibits interesting electronic and magnetic properties. Influence of oxygen vacancies on the electrical response of nanocrystalline SrFeO2.91 as a function of temperature is investigated using impedance spectroscopy technique. A change observed in the Nyquist plot at 383 K has been analyzed in terms of localized and delocalized eg electrons. An unusual and interesting temperature-induced semiconductor to metal-like transition is observed in the frequency-dependent real part of dielectric permittivity. Dependence of frequency on the real and imaginary parts of impedance with respect to temperature supports the presence of semiconductor to metal-like transition in SrFeO2.91.