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, ...
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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.
Mohini Mishra; Raju Kumar Gupta
Abstract
The present work demonstrates a simple and efficient route to synthesize a variety of barium titanate (BaTiO3) nanostructures including nanowires, nanoswords, nanostars, nanocubes, and nanoparticles by a facile hydrothermal approach. The experiments showed that different morphologies can easily be tuned ...
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The present work demonstrates a simple and efficient route to synthesize a variety of barium titanate (BaTiO3) nanostructures including nanowires, nanoswords, nanostars, nanocubes, and nanoparticles by a facile hydrothermal approach. The experiments showed that different morphologies can easily be tuned by varying the concentration of precursors, i.e., hydrogen titanate (H2Ti3O7) and barium hydroxide octahydrate (Ba(OH)2.8H2O), while keeping the molar ratio, reaction temperature and time fixed. The structure and morphology of BaTiO3 were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicate that BaTiO3 nanowires are in cubic phase with an average diameter of 80-100 nm. The shape of BaTiO3 changes from nanowires to nanoparticles with an increase in Ba(OH)2.8H2O concentration from 0.08 M to 0.51 M. Two possible mechanisms, in-situ topotactic transformation reaction and dissolution-deposition reaction have been suggested for different morphologies of BaTiO3. The synthesized 0-D and 1-D BaTiO3 nanostructures are promising materials for many applications because of their excellent dielectric, ferroelectric and piezoelectric properties. The present work will open a new route to single reaction parameter dependent synthesis of 0- and 1-D BaTiO3 nanostructures which can find a range of applications including electronics, catalysis, energy harvesting, etc.
Mrinal Kanti Adak; Prasanta Dhak; Atreyee Kundu; Debasis Dhak
Abstract
In this present work, nanocrystalline Co 2+ and Ta 5+ substituted barium bismuth niobate Ba0.5Co0.5Bi2NbTaO9 was synthesized by chemical process. Room temperature single phase, tetragonal structure was confirmed using X-ray diffraction (XRD) study. Average crystallite and particle sizes were found to ...
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In this present work, nanocrystalline Co 2+ and Ta 5+ substituted barium bismuth niobate Ba0.5Co0.5Bi2NbTaO9 was synthesized by chemical process. Room temperature single phase, tetragonal structure was confirmed using X-ray diffraction (XRD) study. Average crystallite and particle sizes were found to be 33 nm and 40 nm, when analyzed through XRD and transmission electron microscopy (TEM) respectively. Field emission scanning electron microscopy (FESEM) was used for micro-structural investigation of samples sintered at 950?C for 4h. The investigation revealed that the material was exhibiting high dielectric constant value of 1017 at Curie temperature (Tc), 500?C when measured at 10 kHz. Impedance spectroscopy analysis showed that above 425?C, the material exhibited both bulk and grain boundary conductivities which were evidenced from FESEM studies. Density of states, minimum hoping distance, binding energy etc. were studied along with other electrical properties from impedance analysis. Hysteresis behavior was also investigated using polarization study.
M. Roy; S. Sahu; S. K. Barbar; S. Jangid
Abstract
Polycrystalline ceramic samples of pure and Cu +2 doped Bi4V2-xCuxO11(x=0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The dielectric constant and dielectric loss and hence ac conductivity as a function of frequency and temperature have been measured. ...
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Polycrystalline ceramic samples of pure and Cu +2 doped Bi4V2-xCuxO11(x=0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The dielectric constant and dielectric loss and hence ac conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy and hence its ac conductivity increases with the increase of temperature. The dc conductivity of material has been measured as a function of temperature from room temperature to 653 K and its activation energy was calculated using the relation σ = σo exp (- Ea/kT). The dc conductivity increases with the substitution of Cu on the vanadium site. The Modulated Differential Scanning Calorimetry (MDSC) has been used to investigate the effect of substitution on the phase transition of the compounds. The results are discussed in detail.
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 ...
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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.
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.
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.
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.
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