Ajay Kumar Behera; Nilaya K. Mohanty; Banarji Behera; Pratibindhya Nayak
Abstract
The polycrystalline sample of 0.7(BiFeO3)-0.3(PbTiO3) [0.7(BFO)-0.3(PT)] was prepared by a high temperature solid state reaction technique. Studies of structural analysis confirm the formation of the compound with rhombohedral structure at room temperature. The electrical properties (impedance, modulus ...
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The polycrystalline sample of 0.7(BiFeO3)-0.3(PbTiO3) [0.7(BFO)-0.3(PT)] was prepared by a high temperature solid state reaction technique. Studies of structural analysis confirm the formation of the compound with rhombohedral structure at room temperature. The electrical properties (impedance, modulus and conductivity) of the material were analyzed using a complex impedance spectroscopy technique in a wide temperature (225-300 o C) and frequency (10 2 -10 6 Hz) range. The studied material exhibits a significant contribution of grain (bulk) effect and non-Debye of relaxation process. The bulk resistance decreases with rise in temperature which exhibits negative temperature coefficient of resistance (NTCR) behavior. Electrical modulus study confirms the presence of bulk effect in the material. This compound also exhibits the temperature dependence of relaxation phenomena. The ac and dc conductivity of the materials were found to be increase with increase in temperature. The activation energy of the compound is found to be less than 1eV and suggests the conduction process is of mixed type (ionic-polaronic and singly-ionized oxygen ion vacancies).
K. J. Patel; M. S. Desai; C. J. Panchal
Abstract
Zirconium dioxide thin films were prepared by e-beam evaporation method to study the effect of substrate temperature on the structural, surface morphology, compositional, and optical properties. X-ray diffraction measurement shows that the films grown at 400 ℃ substrate temperature ...
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Zirconium dioxide thin films were prepared by e-beam evaporation method to study the effect of substrate temperature on the structural, surface morphology, compositional, and optical properties. X-ray diffraction measurement shows that the films grown at 400 ℃ substrate temperature have monoclinic crystal structure. The root mean square surface roughness of the film increases with increase in the substrate temperature. The optical transmittance spectra indicate an average 80% transmittance in the visible region of light. The optical energy band gap of ZrO2 thin film decreases from 5.68 to 5.63 eV as the substrate temperature increases from room temperature to 400 ℃, respectively.
Meera Rawat; K. L. Yadav; Amit Kumar; Piyush Kumar Patel; Nidhi Adhlakha; Jyoti Rani
Abstract
Polycrystalline (Bi0.5Na0.5)1-xBaxTiO3 [here after BNBT], x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1 ceramics have been synthesized by conventional solid state reaction process and were characterized by X-ray diffraction technique, which indicates that on substitution of Ba 2+ in Bi0.5Na0.5TiO3 (BNT) ceramic ...
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Polycrystalline (Bi0.5Na0.5)1-xBaxTiO3 [here after BNBT], x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1 ceramics have been synthesized by conventional solid state reaction process and were characterized by X-ray diffraction technique, which indicates that on substitution of Ba 2+ in Bi0.5Na0.5TiO3 (BNT) ceramic there is splitting of the (2 0 0) peak for x ≥ 0.06. This splitting in the peak position reveals that the composition BNBT-0.06 is well in Morphotropic Phase Boundary (MPB) region where rhombohedral and tetragonal phase co-exist. Scanning electron micrograph shows decrease in grain size from 0.66 to 0.53 μm with increasing concentration of Ba 2+ ; and the dielectric constant of Ba 2+ doped BNT ceramics increased with decreasing grain sizes and a maximum value was attained at size of 0.54 ~ 0.56 μm. Doped BNT ceramic also exhibit diffuse phase transition and are characterised by a strong temperature and frequency dispersion of the permittivity which would be connected with the cation disorder in A-site of perovskite unit cell. Complex impedance spectroscopy is used to analyze the electrical behaviour of BNBT, which indicates the presence of grain effect and the composition exhibits Negative Temperature coefficient of resistance (NTCR) behaviour. The compounds exhibit Arrhenius type of electrical conductivity and the presence of non-Debye type of relaxation has been confirmed from impedance analysis.
N. K. Singh; Radheshyam Rai;Andrei L. Kholkin; Pritam Kumar
Abstract
Polycrystalline samples of BaFe0.5Nb0.5O3 and (1-x)Ba(Fe0.5Nb0.5)O3-xBaTiO3, [referred as BFN and BFN-BT respectively] (x = 0.00, 0.15 and 0.20) have been synthesized by a high-temperature solid-state reaction technique. The formation of the compound was checked by an X-ray diffraction (XRD) technique. ...
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Polycrystalline samples of BaFe0.5Nb0.5O3 and (1-x)Ba(Fe0.5Nb0.5)O3-xBaTiO3, [referred as BFN and BFN-BT respectively] (x = 0.00, 0.15 and 0.20) have been synthesized by a high-temperature solid-state reaction technique. The formation of the compound was checked by an X-ray diffraction (XRD) technique. The microstructure analysis was done by scanning electron micrograph. The spectroscopic data presented in impedance plane show the grain and grain boundary contributions towards electrical processes in the form of semi-circular arcs. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz–5MHz) and temperatures (30-282°C) showed that these properties are strongly temperature and frequency dependent.
Punita Srivastava;Kedar Singh
Abstract
We have developed successfully the synthesis of highly yielded CdSe nanoparticles (NPs) at 60 0C by solvothermal route in which the cadmium and selenium precursors have been dissolved in deionized water, ethylene glycol and hydrazine hydrate. This route is very facile, inexpensive and less hazardous ...
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We have developed successfully the synthesis of highly yielded CdSe nanoparticles (NPs) at 60 0C by solvothermal route in which the cadmium and selenium precursors have been dissolved in deionized water, ethylene glycol and hydrazine hydrate. This route is very facile, inexpensive and less hazardous and ensures almost complete yield of the precursors. The powder product was well characterized by powder X- ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), UV-Vis spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) .It is investigated that as synthesized powder has a hexagonal (Wurtzite) structure of CdSe with diameters of the particles are in the range of 10-15 nm. The formation mechanism is also discussed.
Manauti M. Salunkhe; S. M. Patil; R. M. Mane; S. V. Patil; P. N. Bhosale
Abstract
Molybdenum bismuth telluride thin films have been prepared on clean glass substrate using Arrested Precipitation Technique (APT) which is based on self organized growth process. As deposited MoBi2Te5 thin films were dried in constant temperature oven at 110 o C and further characterized for their optical, ...
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Molybdenum bismuth telluride thin films have been prepared on clean glass substrate using Arrested Precipitation Technique (APT) which is based on self organized growth process. As deposited MoBi2Te5 thin films were dried in constant temperature oven at 110 o C and further characterized for their optical, structural, morphological, compositional and electrical analysis. Optical absorption spectra recorded in the wavelength range 300-800 nm showed band gap (Eg) 1.44 eV. X-ray diffraction pattern and scanning electron microscopic images showed that MoBi2Te5 thin films were nanocrystalline having rhombohedral structure. The energy dispersive spectroscopic analysis of as deposited thin films showed close agreements in theoretical and experimental atomic percentages of Mo 4+ , Bi 3+ and Te 2- and suggest that the chemical formula MoBi2Te5 assigned to molybdenum bismuth telluride thin film material is confirm. The resistivity and thermoelectric power measurement studies showed that the films were semiconducting with n-type conduction. The fill factor and conversion efficiency (η) are determined by fabricating PEC cell using MoBi2Te5 thin film electrode. In this article we report the optostructural, morphological, compositional and thermoelectric characteristics of nanocrystalline MoBi2Te5 thin films to check its suitability as photoelectrode in PEC Cell.
Abstract
Dielectric spectroscopy is applied to investigate the electrical properties of a barium neodymium niobate, Ba(Nd0.5Nb0.5)O3 (BNN) in a temperature range from 323 K to 453 K and in the frequency range from 50 Hz to 1 MHz. The X-ray diffraction of the sample at room temperature shows a tetragonal phase. ...
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Dielectric spectroscopy is applied to investigate the electrical properties of a barium neodymium niobate, Ba(Nd0.5Nb0.5)O3 (BNN) in a temperature range from 323 K to 453 K and in the frequency range from 50 Hz to 1 MHz. The X-ray diffraction of the sample at room temperature shows a tetragonal phase. The scanning electron micrograph of the sample shows the average grain size of BNN ~ 1.92 mm. An analysis of the dielectric constant (e ¢) and loss tangent (tand) with frequency is performed assuming a distribution of relaxation times. The low frequency dielectric dispersion corresponds to DC conductivity. The logarithmic angular frequency dependence of loss peak is found to obey an Arrhenius law with activation energy of 0.55 eV. The frequency dependence of electrical data is also analyzed in the framework of conductivity and electric modulus formalisms. Both these formalisms show qualitative similarities in relaxation times. The scaling behavior of tangent loss (tanδ) suggests that the distribution of relaxation times is temperature independent in BNN.
Subrat K. Barik; R.N.P. Choudhary; A.K. Singh
Abstract
The AC impedance and conductivity properties of Ba0.8Sr0.2TiO3 ceramics in a wide frequency range at different temperatures have been studied. The compound was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis of the compound by X-ray diffraction technique ...
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The AC impedance and conductivity properties of Ba0.8Sr0.2TiO3 ceramics in a wide frequency range at different temperatures have been studied. The compound was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis of the compound by X-ray diffraction technique confirmed its single phase. An ac impedance spectroscopic technique was used to correlate between the microstructure and electrical properties of the compound. The presence of both grain (bulk) and grain boundary effect in the compound was observed. The frequency-dependent electrical data were used to study the conductivity mechanism. An analysis of the electric impedance and modulus with frequency at different temperatures has provided some information to support suggested conduction mechanism.
Komal Bapna; R.J. Choudhary; D.M. Phase
Abstract
We have prepared 4 at.% Fe doped TiO2 thin films on LAO (001) and Si (111) substrates by pulsed laser deposition. X-ray diffraction (XRD) studies suggest different structural properties of the films on the different substrates. Raman measurements corroborate the XRD findings. The thicknesses of the films ...
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We have prepared 4 at.% Fe doped TiO2 thin films on LAO (001) and Si (111) substrates by pulsed laser deposition. X-ray diffraction (XRD) studies suggest different structural properties of the films on the different substrates. Raman measurements corroborate the XRD findings. The thicknesses of the films are also different on the two substrates, suggesting different nucleation process on the two substrates. Interestingly on both the substrates, Fe is not in metal clusters, suggesting their possible incorporation in TiO2 matrix.
N.K. Singh; Pritam Kumar; Radheshyam Rai
Abstract
Dielectric properties of (1-x)Ba(Fe0.5Nb0.5)O3-xBaTiO3 (where x = 0.00, 0.05 and 0.10) solid solution ceramics at high temperature range of RT ~ 270 o C have been characterized in this paper. The above said polycrystalline ceramics with (x = 0.0, 0.05 and 0.10) have been produced via a mixed oxide route. ...
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Dielectric properties of (1-x)Ba(Fe0.5Nb0.5)O3-xBaTiO3 (where x = 0.00, 0.05 and 0.10) solid solution ceramics at high temperature range of RT ~ 270 o C have been characterized in this paper. The above said polycrystalline ceramics with (x = 0.0, 0.05 and 0.10) have been produced via a mixed oxide route. The effects of BaTiO3 substitution on the structure and on the electrical and ferroelectric properties of Ba(Fe0.5Nb0.5)O3 samples have been studied by performing x-ray diffraction and dielectric measurements. The dielectric properties (e¢ and tan d) were investigated in the temperature range of 30-270 °C and in the frequency range of 100 Hz-5 MHz. The variation of relative dielectric permittivity (tan d) and tangent loss (tan d) has suggested a significant role of hopping of trapped charge carriers, which is resulted in an extra dielectric response in addition to the dipole response. It is observed that: (i) the relative dielectric permittivity and tangent loss (tan d) are dependent on frequency, (ii) the temperature of dielectric permittivity maximum shifts toward lower temperature side and (iii) dielectric permittivity and tangent loss rapidly increase by making solid solution of BFN with BaTiO3. X-ray diffraction analysis of the compound suggests the formation of single-phase compound with monoclinic structure. SEM photographs exhibit the uniform distribution of grains. The maximum ferroelectric transition temperature (Tc) of this system was 250-270 °C with the dielectric constant peak of 72500 at 1.09 kHz for x = 0.05.
C. Sekar; K. Suguna
Abstract
Calcium hydrogen phosphate dihydrate (CaHPO4.2H2O, CHPD) or brushite crystal is a well known urinary substance found frequently in urinary stones. The CHPD crystals have been crystallized in sodium metasilicate gel (SMS) at room temperature under pH 6 in the presence of sodium fluoride. Here, H3PO4 and ...
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Calcium hydrogen phosphate dihydrate (CaHPO4.2H2O, CHPD) or brushite crystal is a well known urinary substance found frequently in urinary stones. The CHPD crystals have been crystallized in sodium metasilicate gel (SMS) at room temperature under pH 6 in the presence of sodium fluoride. Here, H3PO4 and CaCl2 were used as reactants which resulted in simultaneous crystallization of mostly dentritic brushite crystals and a small quantity of hydroxyapatite (HA). On the other hand, use of Na2HPO4 and CaCl2 as reactants yielded the large quantity of HA along with platelet brushite crystals. In both the cases, addition of sodium fluoride is found to inhibit the nucleation and subsequent growth of brushite crystals. The crystal morphology, structure and elemental composition of the grown crystals have been analyzed using SEM-EDX and powder XRD studies. Functional groups present in the grown crystals have been confirmed from the vibrational frequencies of the recorded FTIR spectrum.
N.K. Singh; Pritam Kumar
Abstract
Defect pyrochlore-type Y2(Ba0.5R0.5)2O7 (R = W, Mo) oxides ceramics were prepared by using high-temperature solid-state reaction technique. Preliminary studies of X-ray diffraction (XRD) patterns and scanning electron micrographs (SEM) of the compounds at room temperature suggested that compounds have ...
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Defect pyrochlore-type Y2(Ba0.5R0.5)2O7 (R = W, Mo) oxides ceramics were prepared by using high-temperature solid-state reaction technique. Preliminary studies of X-ray diffraction (XRD) patterns and scanning electron micrographs (SEM) of the compounds at room temperature suggested that compounds have single phase orthorhombic structures and uniform grain distribution throughout the surface of the samples. Detailed studies of dielectric and electrical properties of the materials in a wide range of frequency (1 kHz–1MHz) and temperatures (23–344°C) showed that these properties are strongly temperature and frequency dependent. Variation of dielectric constant (ε') and tangent loss (tanδ) as a function temperatures showed the abnormal behavior around 132°C at 10 kHz and 141°C at 30 kHz of Y2(Ba0.5W0.5)2O7 and around 293°C at 10 kHz and 305°C at 30 kHz of Y2(Ba0.5Mo0.5)2O7 ceramics respectively.
Arun Chamola; Hemant Singh; U.C. Naithani; Shubhash Sharma; Uday Prabhat; Pratiksha Devi; Anuradha Malik; Alok Srivastava; R.K. Sharma
Abstract
In the present work, structural, dielectric and electrical properties of lead zirconate titanate and CaCu3Ti4O12 ceramic composite with composition (1-x)Pb(Zr0.65Ti0.35)O3 - xCaCu3Ti4O12 (where x = 0, 0.20, 0.40 and 0.60) has been reported. The sample was prepared by employing a high-temperature solid-state ...
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In the present work, structural, dielectric and electrical properties of lead zirconate titanate and CaCu3Ti4O12 ceramic composite with composition (1-x)Pb(Zr0.65Ti0.35)O3 - xCaCu3Ti4O12 (where x = 0, 0.20, 0.40 and 0.60) has been reported. The sample was prepared by employing a high-temperature solid-state reaction technique. X-ray diffraction studies confirm the formation of pure phase for x = 0.00 concentration and composite phases for the x = 0.40, 0.60 compositions. Doublet of diffraction peaks suggests structural change for x = 0.20 composition. Scanning electron micrographs show a uniform grain distribution and the grain size and shape modified upon CaCu3Ti4O12 addition. Dielectric measurement demonstrates a decrease in the dielectric constant with increase in CaCu3Ti4O12 percentage. The prepared ceramic composites have high dielectric constant and low dielectric loss. The temperature dependence of the ac conductivity indicated that the conduction process is due to singly ionized (in ferroelectric region) and doubly ionized (in paraelectric region).
Abhay D. Deshmukh; S. J. Dhoble; N.S. Dhoble
Abstract
The MAl12O19:Eu (M = Ca, Ba, Sr) phosphor were synthesized by combustion method and systematically characterized by photoluminescence excitation and emission spectra, concentration quenching, morphology and X-ray mapping with scanning electron microscopy. In SrAl12O19:Eu phosphor two PL emission peaks ...
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The MAl12O19:Eu (M = Ca, Ba, Sr) phosphor were synthesized by combustion method and systematically characterized by photoluminescence excitation and emission spectra, concentration quenching, morphology and X-ray mapping with scanning electron microscopy. In SrAl12O19:Eu phosphor two PL emission peaks are observed at about 389 nm and another around 420 nm as well as BaAl12O19:Eu phosphor shows blue emission around 460 nm is observed in the blue region of the spectrum and CaAl12O19:Eu shows only red emission at 592 as well as 615 nm. Both phosphors can be efficiently excited in the wavelength range of 250-425 nm, where the near UV (~320 nm) solid state excitation is matched. By combining MAl12O19:Eu (M = Ca, Ba, Sr) phosphor with near UV chops emitting intense blue green (Ba), yellow-red (Ca) and blue purple (Sr) LEDs white LEDs can be produced.
Pritam Kumar; B.P. Singh; T.P. Sinha; N.K. Singh
Abstract
The complex perovskite oxide barium gadolinium niobate, Ba(Gd0.5Nb0.5)O3 (BGN) is synthesized by a solid-state reaction technique. The X-ray diffraction of the sample at room temperature shows a tetragonal phase. The scanning electron micrograph of the sample shows the average grain size of BGN ...
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The complex perovskite oxide barium gadolinium niobate, Ba(Gd0.5Nb0.5)O3 (BGN) is synthesized by a solid-state reaction technique. The X-ray diffraction of the sample at room temperature shows a tetragonal phase. The scanning electron micrograph of the sample shows the average grain size of BGN ~ 1.92 mm. The frequency-dependent dielectric dispersion of BGN is investigated in the temperature range from 303 K to 463 K and in a frequency range from 50 Hz to 1 MHz by impedance spectroscopy. The logarithmic angular frequency dependence of loss peak is found to obey an Arrhenius law with activation energy of 0.70 eV. It is observed that: (i) the dielectric constant (e¢ ) and loss tangent (tan d) are dependent on frequency, (ii) the temperature of dielectric constant maximum shift toward lower temperature side, (iii) The scaling behavior of dielectric loss spectra suggests that the relaxation describes the same mechanism at various temperatures.
N. K. Singh; Pritam Kumar; Hemchand Kumar; Radheshyam Rai
Abstract
The polycrystalline samples of the pyrochlore-type Dy2(Ba0.5R0.5)2O7 (R = W, Mo) compounds have been prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction (XRD) studies and scanning electron micrographs (SEM) of the compounds at room temperature suggested that compounds ...
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The polycrystalline samples of the pyrochlore-type Dy2(Ba0.5R0.5)2O7 (R = W, Mo) compounds have been prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction (XRD) studies and scanning electron micrographs (SEM) of the compounds at room temperature suggested that compounds have single phase orthorhombic crystal structures and grain distribution throughout the surface of the samples was uniform. Dielectric studies (dielectric constant (e´) and tangent loss (tan δ) obtained both as a function of frequency (4 kHz -1 MHz) at room temperature (RT) and temperature (RT 320 0 C) at 20 kHz and 100 kHz suggest that compounds do not have dielectric anomaly in the said frequency and temperature range.