Vinayak M Adimule; Debdas Bhowmik; Adarsha Haramballi Jagadeesha
Abstract
Gadolinium (Gd) doped titanate nanostructures (NS) with a new set of 10-50 wt. % of Gd were synthesized by microwave-assisted hydrothermal and reduction using hydrazine hydrate. The crystal structure has been evaluated with SEM (scanning electron microscopy) analysis exhibited rod like geometry of nanoparticles ...
Read More
Gadolinium (Gd) doped titanate nanostructures (NS) with a new set of 10-50 wt. % of Gd were synthesized by microwave-assisted hydrothermal and reduction using hydrazine hydrate. The crystal structure has been evaluated with SEM (scanning electron microscopy) analysis exhibited rod like geometry of nanoparticles (NPs). XRD (X-ray diffraction spectroscopy) analysis of GdTiO3 and undoped titanate nanostructure (NS) intense peak exhibited crystal tetragonal structure. CV (cyclic voltammetry) exhibited an oxidation potential of 50 wt. % of GdTiO3 was found to be - 0.54 eV. UV-Visible spectroscopic revealed absorptivity of 50 wt. % of GdTiO3 was found to be 650 nm (visible region) and undoped titanate absorptivity at 320 nm (UV region). The pelletized nanostructures of GdTiO3 were investigated for current-voltage (I-V), capacitance-voltage (C-V), resistance-voltage (R-V) measurements, which showed frequency range in between 1 kHz to 2 MHz and 50 wt. % GdTiO3 NS showed a decreasing trend in admittance value with an increase in frequency. However, an increase in the conductance, power dissipation values with a decrease in resistivity, and increase in the frequency has been noticed which embark considerable variation in conductivity and power dissipation in GdTiO3 NS. The results from the plots of current-voltage (I-V), capacitance-voltage (C-V), and bias voltage with an applied frequency of the GdTiO3 NS has been discussed.
M. R. Eraky; Mohamed Th. S. Heikal
Abstract
We address a vesicular basalt sample from Jabel Isbil Volcano that is located in Dhamar-Rada'a Volcanic Field (DRVF), SE Sana'a, Yemen. The studied vesicular basalt represents the main rock type at the top-hill volcano, whereas olivine basalt and mugearite represent the foot-hill and middle-hill volcano, ...
Read More
We address a vesicular basalt sample from Jabel Isbil Volcano that is located in Dhamar-Rada'a Volcanic Field (DRVF), SE Sana'a, Yemen. The studied vesicular basalt represents the main rock type at the top-hill volcano, whereas olivine basalt and mugearite represent the foot-hill and middle-hill volcano, respectively. Therefore, the present investigation stresses on vesicular basalt after thermal treatment processes. Our measurements revealed that the samples have semiconducting behavior with high electrical resistivity. Moreover, the dielectric constant has low/constant values. Electrical resistivity reached 1.2 G.ohm.m at room temperature. The authors strongly recommend that the vesicular basalts elsewhere give rise to high economic and strategic potential of high technologies.
Robiul Islam Rubel; Md. Hasan Ali; Md. Abu Jafor; Sk. Suzauddin Yusuf
Abstract
The modern manufacturing technology tends to innovate different materials with simultaneous low density in weight, porosity, high toughness, corrosion resistance, thermal and electrical properties etc. Metallic matrix-based carbon nanotubes composites (CNTs) are a relatively new material concept. The ...
Read More
The modern manufacturing technology tends to innovate different materials with simultaneous low density in weight, porosity, high toughness, corrosion resistance, thermal and electrical properties etc. Metallic matrix-based carbon nanotubes composites (CNTs) are a relatively new material concept. The CNT reinforced composite materials harvest the dual benefit of alloying metals with high mechanical properties of CNTs. Besides, the materials being innovated must have good forming or machining characteristics. However, no machining data or machining model are yet available for these newly developed composites. In this work, the mechanical machining of metal-matrix/CNTs composites has studied to review the available data and better understanding the material removal behaviour. The work also concludes on the suggestive machining techniques adopted that will not affect the structural deformation, mechanical, thermal, electrical properties as well as must not alter the mechanical characteristics of the machined surface. The present study will assist in optimizing the manufacturing composites with desirable mechanical properties in future CNT reinforced composite developments. Copyright © VBRI Press.
Pallavi S.G; Vishnumurthy K.A.; K. Natarajan
Abstract
In this paper, ammonia sensor operating at room temperature based on diphenylamine conjugated polymer has been designed and developed. The structure of the polymer was established by UV-Visible, FT-IR and NMR characterization techniques. The polymer was doped with silver nanoparticles by ex-situ method ...
Read More
In this paper, ammonia sensor operating at room temperature based on diphenylamine conjugated polymer has been designed and developed. The structure of the polymer was established by UV-Visible, FT-IR and NMR characterization techniques. The polymer was doped with silver nanoparticles by ex-situ method in 0.6 wt%, 1.2wt% and 1.8wt% to form silver nano-composites. The thin films of the polymer and its composites were cast by spin coating on the glass plate. The response of the polymer and its composite with silver nanoparticles has been studied for gas sensor applications. The polymer showed selectivity towards ammonia gas, whereas the polymer composite with silver nanoparticles exhibited selectivity towards ammonia gas and also to ethanol vapors. The response towards ammonia gas was found to increase with the increase in loading of silver nanoparticles. Reproducibility of the polymer and its composite is studied and is found to improve with the loading of silver nanoparticles.
Shweta Thakur; Seema Sharma;Ashutosh Tiwari; Radheshyam Rai
Abstract
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have ...
Read More
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have pure pervoskite phase with tetragonal structure at room temperature and have maximum value of dielectric constant at x = 0.9. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz–1MHz) and temperatures (30 – 500 o C) showed that properties are strongly temperature and frequency dependent. The plots of Zʹʹ and Mʹʹ versus frequency at various temperatures show peaks in the higher temperature range (>300 o C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.
Rakesh Kumar; Seema Joon; Avanish P. Singh; Brij P. Singh; S. K. Dhawan
Abstract
In response to the striking research activity and publications in fabrication of multifunctional materials, the present work is an attempt to fabricate processible composite sheets of poly (o-anisidine)-carbon fiber (PoACF) by a facile, low cost method and find their use in electromagnetic interference ...
Read More
In response to the striking research activity and publications in fabrication of multifunctional materials, the present work is an attempt to fabricate processible composite sheets of poly (o-anisidine)-carbon fiber (PoACF) by a facile, low cost method and find their use in electromagnetic interference (EMI) shielding in X-band (8.2-12.4 GHz). PoACF composite is synthesized by in-Situ oxidative emulsion polymerization and transformed into thin sheets by compression molding technique using different ratio of phenolic novolac resin as a binder. The prepared PoACF composites and sheets are characterized by SEM, TGA, UV-vis, & FT-IR techniques. PoACF sheets have conductivity of the order of 10 -3 to 10 -1 S/cm and maximum shielding effectiveness of 32.57 dB at 4 mm thickness. These sheets have flexural strength between 18.82 to 41.28 MPa. The sheets of PoACF composite have sufficient thermal as well as mechanical stability and may be accepted as an economical material for EMI shielding application.
Sonika Thakur; Anupinder Singh; Lakhwant Singh
Abstract
Self-standing polyaniline (Pani) films modified with gold nanoparticles (Au NP’s), where Au NP’s are added in different successive weight percents, have been synthesized by conventional chemical polymerization technique. An in-depth investigation of the structural and electrical characteristics ...
Read More
Self-standing polyaniline (Pani) films modified with gold nanoparticles (Au NP’s), where Au NP’s are added in different successive weight percents, have been synthesized by conventional chemical polymerization technique. An in-depth investigation of the structural and electrical characteristics of prepared films has been conducted using various characterizations. The X-ray diffraction (XRD) validates the presence of Au NP’s in Pani and the results are supported well by energy dispersive X-ray analyzer (EDX). The field emission scanning electron microscopy (FESEM) clearly shows thorough dispersion of Au NP’s in the amorphous host matrix with minor aggregation. The Fourier transform infrared red (FTIR) studies give the information of possible chemical interaction between the nanoparticles and polymer which is in good agreement with charge transfer mechanism proposed in the manuscript. The temperature dependent dc electrical conductivity has been observed to depend strongly on the nanoparticle loading and follows Mott’s three-dimensional variable range hopping (3D VRH) conduction mechanism. Parameters obtained from Hall Effect measurements are of same order as is calculated by dc measurements which indicates a very good corroboration of results. Higher ac conductivity, dielectric constant and dielectric loss of nanocomposites have also been observed as compared to that of pure Pani.
R. K. Goyal; R. Sulakhe
Abstract
The preparation, electrical and thermal properties of nickel (Ni) particles filled poly(vinylidene fluoride) (PVDF) composites were discussed in this paper. The experimental density of the composites was close to that of theoretical density. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy ...
Read More
The preparation, electrical and thermal properties of nickel (Ni) particles filled poly(vinylidene fluoride) (PVDF) composites were discussed in this paper. The experimental density of the composites was close to that of theoretical density. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that PVDF has primarily α-phase. The coefficient of thermal expansion of the composites decreased approximately 30 % compared to pure PVDF. The percolation threshold of the composite is about 5 vol% Ni, which is less than one-third of the value reported for metal filled polymer composites in the literature. The significantly lower percolation was attributed to the increased crystallinity and the better processing method which results in an easy formation of 3-dimensional network of Ni particles in the matrix, as confirmed by scanning electron microscopy (SEM). The electrical conductivity of these composites increased from 6.3×10 -13 S/cm to 2.6×10 -1 S/cm which is better and comparable than those of required for antistatic (10 -4 -10 -8 S/cm) and electromagnetic interference (EMI) shielding applications. The significant increase in electrical and thermal properties showed that these composites might be potential candidates for the EMI shielding and antistatic devices.
N. Bouazizi; R. Bargougui; A. Oueslati; R. Benslama
Abstract
CuO nanopowder oxide was synthesized by reflux condensation method without any surfactants or templates, using copper nitrate in deionized water and aqueous ammonia solution. The structural, optical and electrical properties of the sample were investigated using X-ray diffraction (XRD), FT-IR, UV–visible ...
Read More
CuO nanopowder oxide was synthesized by reflux condensation method without any surfactants or templates, using copper nitrate in deionized water and aqueous ammonia solution. The structural, optical and electrical properties of the sample were investigated using X-ray diffraction (XRD), FT-IR, UV–visible spectroscopy and impedance spectroscopy measurements. The X-ray diffraction patterns revealed that CuO nanoparticles (NPs) was formed in pure monoclinic phase and good crystalline quality, whose NPs sizes were of the order 25 nm which an average size can be tailored by the synthesis time. FT-IR spectra of CuO NPs used to detect the possible adsorbed species on the CuO materials. In addition, the peaks at 529 and 604 cm-1 correspond to the characteristic stretching vibrations of Cu-O bond in the monoclinic CuO. The optical absorption property has been determined by UV–visible Spectroscopy in the wavelength range of 200–800 nm which indicate the energy gap (Eg). As result, Eg increases with increasing the synthesis time from 2.72 to 1.87 eV. The complex measurement has been investigated at room temperature, and in the frequency range 40 Hz–100 kHz, showing that Nyquist plots (Z' versus Z'') are well fitted to an equivalent circuit model which consists of a parallel combination of a bulk resistance Rb and constant phase elements CPE. On the other hand, the capacitance and the conductance of CuO NPs have a proportional relationship to the charge transfer and the surface electrode-pallet. These properties make these materials very promising electrode.
Sunita Rattan; Prachi Singhal; Devesh Kumar Avasthi; Ambuj Tripathi
Abstract
Ion implantation is a surface treatment process in which the surface of a sample is bombarded with a beam of energetic dopant ions to implant ions into the matrix of the substrate. In the present work, nanocomposites of poly(3,4-ethylenedioxy thiophene) /poly(4-styrene sulphonate) (PEDOT: PSS) and nanographite ...
Read More
Ion implantation is a surface treatment process in which the surface of a sample is bombarded with a beam of energetic dopant ions to implant ions into the matrix of the substrate. In the present work, nanocomposites of poly(3,4-ethylenedioxy thiophene) /poly(4-styrene sulphonate) (PEDOT: PSS) and nanographite are prepared and subjected to swift heavy ion implantation using the same ion as that of the filler in the nanocomposites. PEDOT: PSS/ nanographite nanocomposites have been synthesized by solution blending method. The prepared PEDOT: PSS/ nanographite nanocomposite films were irradiated with carbon ions (C ion beam, 50 MeV) in fluence range of 3 × 10 10 to 3 × 10 12 ions/cm 2 . The nanocomposite films were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) before and after C ion implantation and were evaluated for their electrical and sensor properties. SEM and XRD studies clearly depict the homogeneous dispersion of nanograhite in polymer matrix along with densification of the polymer nanocomposite. The implanted nanocomposites exhibit better electrical and sensor properties for the detection of nitroaromatics.
Virender P. Singh; Gagan Kumar; Pooja Dhiman; R. K. Kotnala; Jyoti Shah; Khalid M. Batoo; M. Singh
Abstract
In the present work BaFe12O19 nano-hexaferrite had been synthesized by sol-gel method and then characterized for its structural, electric, dielectric and magnetic properties. X-ray diffraction studies confirmed the hexagonal structure of the prepared nanohexaferrite with no secondary phase and the particle ...
Read More
In the present work BaFe12O19 nano-hexaferrite had been synthesized by sol-gel method and then characterized for its structural, electric, dielectric and magnetic properties. X-ray diffraction studies confirmed the hexagonal structure of the prepared nanohexaferrite with no secondary phase and the particle size was found to be of the order of 49 nm. Further, the morphology of the sample has been studied by using transmission electron microscopy (TEM). A high value of the DC resistivity (5.5 × 106 Ω cm), has been obtained at room temperature. The dielectric properties such as dielectric constant (ε′), dielectric loss tangent (tan δ) and ac electrical conductivity (σac) are investigated as a function of frequency. The dielectric constant and loss tangent are found to be decreasing with the increase in frequency while ac electrical conductivity is observed to be increasing with the increase in frequency. The dielectric properties have been explained on the basis of Maxwell-Wagner’s two-layer model and hopping of the charge. The magnetic properties such as initial permeability (µi) and relative loss factor (RLF) have been investigated as a function of frequency in the range 75 kHz to 30 MHz .Fairly constant value of initial permeability and low values of RLF of the order of 10-4 over a wide frequency range are the cardinal achievements of the present work. The room temperature M-H study shows that present nanohexaferrite has high value of coercivity (2151.3 Oe) and high saturation magnetization (32.5 emu/gm), which make present nanohexaferrite very suitable for magnetic applications. The M-T study shows that prepared nano-hexaferrite has high Tc (746 K).
S. Kumari; A. Kumar; P. R. Sengupta; P. K. Dutta; R. B. Mathur
Abstract
Multiwalled carbon nanotubes (MWCNT)- reinforced carbon/copper (C/Cu) composites were developed by powder metallurgy technique and mixed powders of C and Cu were consolidated into plates without using any extra binder followed by sintering at 1000 o C in inert atmosphere. Samples were characterized for ...
Read More
Multiwalled carbon nanotubes (MWCNT)- reinforced carbon/copper (C/Cu) composites were developed by powder metallurgy technique and mixed powders of C and Cu were consolidated into plates without using any extra binder followed by sintering at 1000 o C in inert atmosphere. Samples were characterized for structural, mechanical, electrical and thermal properties w.r.t. different mass fraction of MWCNT in C-Cu matrix. In comparison to C/Cu composite, addition of minute amount (0.25 wt%) of CNT in C-Cu substantially improved the mechanical, electrical and thermal properties of composites. These composites were mechanically stable and strong and exhibited high bending strength of 162 MPa, indicating a homogeneous dispersion of MWCNTs in the C-Cu matrix. Maximum thermal conductivity of 37.60 W/mK perpendicular to the pressing direction was obtained for 0.50 wt% CNT reinforced C-Cu composite exhibiting an improvement of 45% over pure C-Cu composite processed under identical conditions. High thermal conducting and mechanically strong composites can be used as heat sink for long time.
S. K. Shukla; Aparna Shekhar;Ashutosh Tiwari; Anand Bharadavaja
Abstract
The present work reports the synthesis of nano size zinc oxide encapsulated polyanaline by wet-chemical method at ambient condition. The prepared composite was characterized by XRD, SEM, TGA and UV-Vis spectroscopy. The results revealed the formation of the crystalline homogenous ZnO centered composite ...
Read More
The present work reports the synthesis of nano size zinc oxide encapsulated polyanaline by wet-chemical method at ambient condition. The prepared composite was characterized by XRD, SEM, TGA and UV-Vis spectroscopy. The results revealed the formation of the crystalline homogenous ZnO centered composite with electrical conductance in the range of 10 -2 scm -1 and thermal stability up to 280 0 C. Further, electrical resistance of a ZnO/PANi film of ~200 nm thickness was monitored against humidity to use as humidity sensitive element. The observed sensing parameters were response time, 32 sec; and recovery time, 45 sec; sensor has exhibited better sensing characteristics than pure PANi and other reported humidity sensors.
B. B. Mohanty; M. P. K. Sahoo;R. N. P. Choudhary; P. S. Sahoo
Abstract
The polycrystalline Ba3Sr2GdTi3V7O30 material of tungsten bronze structural family was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction analysis exhibits the formation of single-phase compound with orthorhombic crystal system. Surface micrograph recorded by ...
Read More
The polycrystalline Ba3Sr2GdTi3V7O30 material of tungsten bronze structural family was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray diffraction analysis exhibits the formation of single-phase compound with orthorhombic crystal system. Surface micrograph recorded by scanning electron microscopic (SEM) technique has well defined but non-uniformly distributed grains throughout the surface of the pellet sample. Detailed studies of dielectric properties as a function of temperature (306-773 K) and frequencies (10 2 -10 6 Hz) suggest that the compound has frequency independent diffused dielectric anomaly at a temperature ~620 K which may be related to ferroelectric phase transition which is confirmed from polarization study. The frequency and temperature dependence of impedance property of the material were analyzed using a complex impedance spectroscopy. The Nyquist plots confirmed the presence of grain and grain boundary effect in the material.
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. ...
Read More
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.
N. K. Singh; Pritam Kumar; Chandra Prakash
Abstract
Recently a new wave of interest has risen on complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline ceramics of Ba(Fe0.5Nb0.5)O3 (BFN) and its solid solutions 0.89Ba(Fe0.5Nb0.5)O3-0.11BaTiO3 ...
Read More
Recently a new wave of interest has risen on complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline ceramics of Ba(Fe0.5Nb0.5)O3 (BFN) and its solid solutions 0.89Ba(Fe0.5Nb0.5)O3-0.11BaTiO3 (BFN-BT11) and 0.89Ba(Fe0.5Nb0.5)O3-0.11SrTiO3 (BFN-ST11) were fabricated by a solid-state reaction Method. Processing parameters such as calcination temperature, sintering temperature and sintering durations were optimized to get best dielectric properties. It was found that the above ceramics sintered at 1250°C for 6 hours exhibited maximum density and uniform microstructure. X-ray diffraction studies of the compound showed the formation of single-phase monoclinic crystal structure at room temperature. Surface morphology of the compounds was studied by Scanning electron microscope (SEM). The effects of BaTiO3 and SrTiO3 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 electrical properties of the samples were investigated in a frequency range of 100 Hz - 1 MHz and temperature range of 30-350 °C using complex impedance spectroscopic technique. The frequency-dependent electrical data are also analyzed in the framework of conductivity and impedance formalisms.
Subhadarsani Sahoo; Dhiren K. Pradhan; R. N. P. Choudhary; B. K. Mathur
Abstract
The polycrystalline sample of (K0.5Bi0.5)(Fe0.5Nb0.5)O3 was synthesized by a high- temperature solid-state reaction technique. The material crystallizes in cubic structure at room temperature. The dielectric properties of the material were investigated in a temperature range from 30-200 ºC in the ...
Read More
The polycrystalline sample of (K0.5Bi0.5)(Fe0.5Nb0.5)O3 was synthesized by a high- temperature solid-state reaction technique. The material crystallizes in cubic structure at room temperature. The dielectric properties of the material were investigated in a temperature range from 30-200 ºC in the frequency range (102–107 Hz). Impedance data is well fitted using proper equivalent circuit composed of a parallel resistance and capacitance in series with a parallel resistance, constant phase element and a capacitance. The compound shows a typical negative temperature coefficient of resistance type (NTCR) behavior like that of semiconductors. Modulus spectroscopy and dielectric conductivity formalism were employed to study dielectric relaxation phenomena in the material. The frequency dependence of conductivity is well fitted to Jonscher’s single power law.
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. ...
Read More
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.
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 ...
Read More
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.
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 ...
Read More
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 ...
Read More
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.
)
)
)
)