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Papers by Pritam Kumar
Advanced Materials Letters, 2011
Dielectric properties of (1-x)Ba(Fe 0.5 Nb 0.5)O 3-xBaTiO 3 (where x = 0.00, 0.05 and 0.10) solid... more Dielectric properties of (1-x)Ba(Fe 0.5 Nb 0.5)O 3-xBaTiO 3 (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 BaTiO 3 substitution on the structure and on the electrical and ferroelectric properties of Ba(Fe 0.5 Nb 0.5)O 3 samples have been studied by performing x-ray diffraction and dielectric measurements. The dielectric properties ( and tan) 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 () and tangent loss (tan) 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) 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 BaTiO 3. 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 (T c) of this system was 250-270 °C with the dielectric constant peak of 72500 at 1.09 kHz for x = 0.05.
Journal of Advanced Dielectrics, 2011
Polycrystalline samples of samarium barium tungstate [ Sm2(Ba0.5W0.5)2O7 : (SBW)] pyrochlore stru... more Polycrystalline samples of samarium barium tungstate [ Sm2(Ba0.5W0.5)2O7 : (SBW)] pyrochlore structure type oxides have been prepared by a solid-state reaction technique. X-ray diffraction (XRD) patterns of this compound at room temperature suggest the formation of a single phase compound with orthorhombic structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (4 kHz–1 MHz) at room temperature, and as a function of temperature (23–350°C) at 20 and 50 kHz frequencies suggest that the compound does not have dielectric anomaly. The variation of dc resistivity suggests the semiconductor characteristics of the material. The value of activation energy (E a ~ 0.43 at 20 kHz and E a ~ 0.29 at 50 kHz) of the above mentioned compound has been calculated from the slope of the ln σac versus 1/T graph in the high temperature region (> 240°C). The low value of activation energy supports the superionic nature of the compounds in the high tempera...
Advanced Materials Letters, 2010
The polycrystalline samples of the pyrochlore-type Dy 2 (Ba 0.5 R 0.5) 2 O 7 (R = W, Mo) compound... more The polycrystalline samples of the pyrochlore-type Dy 2 (Ba 0.5 R 0.5) 2 O 7 (R = W, Mo) compounds have been prepared by a hightemperature 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 (´) 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.
Solid State Sciences, 2011
Perovskite types Sr(Sm0.5Nb0.5)O3, (SSN) ceramics have been prepared through solid state reaction... more Perovskite types Sr(Sm0.5Nb0.5)O3, (SSN) ceramics have been prepared through solid state reaction route. The scanning electron microscopy provides information on the quality of the samples and uniform grain distribution over the surface of the samples. The field dependence of the dielectric response was measured in a frequency range from 50 Hz to 1 MHz and in a temperature range from 60 °C to 420 °C indicates polydispersive nature of the materials. An analysis of the dielectric constant (ɛ′) and tangent loss (tanδ) with frequency is performed assuming a distribution of relaxation times as confirmed by the scaling behavior of electric modulus spectra. The frequency dependence of the electric modulus peak is found to obey Arrhenius law with activation energy of ∼0.026 eV. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region. 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 imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures in SSN.
Physica B: Condensed Matter, 2011
... 1 Ac conductivity and dielectric relaxation in Ba(Sm 1/2 Nb 1/2 )O 3 ceramic Pritam Kumar a ,... more ... 1 Ac conductivity and dielectric relaxation in Ba(Sm 1/2 Nb 1/2 )O 3 ceramic Pritam Kumar a , BP Singh b , NK Singh a* a Department of Physics, VKS University, Ara-802301, India b University Department of Physics, TM Bhagalpur University, Bhagalpur ... [7]A. Dutta and TP Sinha ...
Journal of Alloys and Compounds, 2011
Polycrystalline samples of BaFe 0.5 Nb 0.5 O 3 and (1 − x)Ba(Fe 0.5 Nb 0.5)O 3-xSrTiO 3 [referred... more Polycrystalline samples of BaFe 0.5 Nb 0.5 O 3 and (1 − x)Ba(Fe 0.5 Nb 0.5)O 3-xSrTiO 3 [referred as BFN and BFN-ST respectively] (x = 0.00, 0.15 and 0.20) have been synthesized by a high-temperature solid-state reaction technique. The XRD patterns of the BFN and BFN-ST at room temperature show a monoclinic phase. The microstructure of the ceramics was examined by the scanning electron microscopy (SEM) and shows the polycrystalline nature of the samples with different grain sizes, which are inhomogeneously distributed through the sample surface. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz-5 MHz) and temperatures (30-270 • C) showed that properties are strongly temperature and frequency dependent. Complex Argand plane plot of ε against ε , usually called Cole-Cole plots is used to check the polydispersive nature of relaxation phenomena in above mentioned compounds. Relaxation phenomena of non-Debye type have been observed in the BFN and BFN-ST ceramics, as confirmed by the Cole-Cole plots.
Journal of Alloys and Compounds, 2010
... Page 1 of 19 Accepted Manuscript 1 Investigation of structural and dielectric behavior of Eu ... more ... Page 1 of 19 Accepted Manuscript 1 Investigation of structural and dielectric behavior of Eu 2 (B 0.5 B 0.5 ) 2 O 7 (B = Ba; B = W, Mo) Ceramics NK Singh a , Pritam Kumar a , OP Roy b and Radheshyam Rai c* a University Department of Physics, VKS ... 28] T. Kar, RNP Choudhary ...
Journal of Alloys and Compounds, 2014
ABSTRACT The frequency-dependent dielectric relaxation of [Pb0.94Sr0.06][(Mn1/3Sb2/3)0.05 (Zr0.52... more ABSTRACT The frequency-dependent dielectric relaxation of [Pb0.94Sr0.06][(Mn1/3Sb2/3)0.05 (Zr0.52Ti0.48)0.95] O3 ceramics, synthesized in pure perovskite phase by a solid-state reaction technique is investigated in the temperature range from 303 to773K by alternating-current impedance spectroscopy. Using Cole-Cole model, an analysis of the imaginary part of the dielectric permittivity with frequency is performed assuming a distribution of relaxation times. The scaling behavior of the imaginary part of the electric modulus (M”) suggests that the relaxation describes the same mechanism at various temperatures. The variation of dielectric constant with temperature is explained considering the space-charge polarization. The SEM indicates that the sample has single phase with an average grain size ∼14.2 μm. The material exhibits tetragonal structure. A detailed temperature dependent dielectric study at various frequencies has also been performed.
Advanced Materials Letters, 2011
Dielectric properties of (1-x)Ba(Fe 0.5 Nb 0.5)O 3-xBaTiO 3 (where x = 0.00, 0.05 and 0.10) solid... more Dielectric properties of (1-x)Ba(Fe 0.5 Nb 0.5)O 3-xBaTiO 3 (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 BaTiO 3 substitution on the structure and on the electrical and ferroelectric properties of Ba(Fe 0.5 Nb 0.5)O 3 samples have been studied by performing x-ray diffraction and dielectric measurements. The dielectric properties ( and tan) 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 () and tangent loss (tan) 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) 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 BaTiO 3. 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 (T c) of this system was 250-270 °C with the dielectric constant peak of 72500 at 1.09 kHz for x = 0.05.
Journal of Advanced Dielectrics, 2011
Polycrystalline samples of samarium barium tungstate [ Sm2(Ba0.5W0.5)2O7 : (SBW)] pyrochlore stru... more Polycrystalline samples of samarium barium tungstate [ Sm2(Ba0.5W0.5)2O7 : (SBW)] pyrochlore structure type oxides have been prepared by a solid-state reaction technique. X-ray diffraction (XRD) patterns of this compound at room temperature suggest the formation of a single phase compound with orthorhombic structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (4 kHz–1 MHz) at room temperature, and as a function of temperature (23–350°C) at 20 and 50 kHz frequencies suggest that the compound does not have dielectric anomaly. The variation of dc resistivity suggests the semiconductor characteristics of the material. The value of activation energy (E a ~ 0.43 at 20 kHz and E a ~ 0.29 at 50 kHz) of the above mentioned compound has been calculated from the slope of the ln σac versus 1/T graph in the high temperature region (> 240°C). The low value of activation energy supports the superionic nature of the compounds in the high tempera...
Advanced Materials Letters, 2010
The polycrystalline samples of the pyrochlore-type Dy 2 (Ba 0.5 R 0.5) 2 O 7 (R = W, Mo) compound... more The polycrystalline samples of the pyrochlore-type Dy 2 (Ba 0.5 R 0.5) 2 O 7 (R = W, Mo) compounds have been prepared by a hightemperature 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 (´) 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.
Solid State Sciences, 2011
Perovskite types Sr(Sm0.5Nb0.5)O3, (SSN) ceramics have been prepared through solid state reaction... more Perovskite types Sr(Sm0.5Nb0.5)O3, (SSN) ceramics have been prepared through solid state reaction route. The scanning electron microscopy provides information on the quality of the samples and uniform grain distribution over the surface of the samples. The field dependence of the dielectric response was measured in a frequency range from 50 Hz to 1 MHz and in a temperature range from 60 °C to 420 °C indicates polydispersive nature of the materials. An analysis of the dielectric constant (ɛ′) and tangent loss (tanδ) with frequency is performed assuming a distribution of relaxation times as confirmed by the scaling behavior of electric modulus spectra. The frequency dependence of the electric modulus peak is found to obey Arrhenius law with activation energy of ∼0.026 eV. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region. 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 imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures in SSN.
Physica B: Condensed Matter, 2011
... 1 Ac conductivity and dielectric relaxation in Ba(Sm 1/2 Nb 1/2 )O 3 ceramic Pritam Kumar a ,... more ... 1 Ac conductivity and dielectric relaxation in Ba(Sm 1/2 Nb 1/2 )O 3 ceramic Pritam Kumar a , BP Singh b , NK Singh a* a Department of Physics, VKS University, Ara-802301, India b University Department of Physics, TM Bhagalpur University, Bhagalpur ... [7]A. Dutta and TP Sinha ...
Journal of Alloys and Compounds, 2011
Polycrystalline samples of BaFe 0.5 Nb 0.5 O 3 and (1 − x)Ba(Fe 0.5 Nb 0.5)O 3-xSrTiO 3 [referred... more Polycrystalline samples of BaFe 0.5 Nb 0.5 O 3 and (1 − x)Ba(Fe 0.5 Nb 0.5)O 3-xSrTiO 3 [referred as BFN and BFN-ST respectively] (x = 0.00, 0.15 and 0.20) have been synthesized by a high-temperature solid-state reaction technique. The XRD patterns of the BFN and BFN-ST at room temperature show a monoclinic phase. The microstructure of the ceramics was examined by the scanning electron microscopy (SEM) and shows the polycrystalline nature of the samples with different grain sizes, which are inhomogeneously distributed through the sample surface. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz-5 MHz) and temperatures (30-270 • C) showed that properties are strongly temperature and frequency dependent. Complex Argand plane plot of ε against ε , usually called Cole-Cole plots is used to check the polydispersive nature of relaxation phenomena in above mentioned compounds. Relaxation phenomena of non-Debye type have been observed in the BFN and BFN-ST ceramics, as confirmed by the Cole-Cole plots.
Journal of Alloys and Compounds, 2010
... Page 1 of 19 Accepted Manuscript 1 Investigation of structural and dielectric behavior of Eu ... more ... Page 1 of 19 Accepted Manuscript 1 Investigation of structural and dielectric behavior of Eu 2 (B 0.5 B 0.5 ) 2 O 7 (B = Ba; B = W, Mo) Ceramics NK Singh a , Pritam Kumar a , OP Roy b and Radheshyam Rai c* a University Department of Physics, VKS ... 28] T. Kar, RNP Choudhary ...
Journal of Alloys and Compounds, 2014
ABSTRACT The frequency-dependent dielectric relaxation of [Pb0.94Sr0.06][(Mn1/3Sb2/3)0.05 (Zr0.52... more ABSTRACT The frequency-dependent dielectric relaxation of [Pb0.94Sr0.06][(Mn1/3Sb2/3)0.05 (Zr0.52Ti0.48)0.95] O3 ceramics, synthesized in pure perovskite phase by a solid-state reaction technique is investigated in the temperature range from 303 to773K by alternating-current impedance spectroscopy. Using Cole-Cole model, an analysis of the imaginary part of the dielectric permittivity with frequency is performed assuming a distribution of relaxation times. The scaling behavior of the imaginary part of the electric modulus (M”) suggests that the relaxation describes the same mechanism at various temperatures. The variation of dielectric constant with temperature is explained considering the space-charge polarization. The SEM indicates that the sample has single phase with an average grain size ∼14.2 μm. The material exhibits tetragonal structure. A detailed temperature dependent dielectric study at various frequencies has also been performed.