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Indu Sharma - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis, characterization and structural refinement of Polycrystalline uranium substituted zirconolite CaZr0.9U0.1Ti2O7
    Radiochimica Acta, 2006
    Co-Authors: Omprakash Shrivastava, Narendra Kumar, Indu Sharma
    Abstract:

    Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution on Zr 4+ cationic sites. This makes them a potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a Solid phase of composition CaZr 0.9 U 0.1 Ti 2 O 7 was synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium, respectively. Solid-state synthesis was carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The Polycrystalline Solid phase was characterized by its typical powder diffraction pattern. Step analysis data were used for ab initio calculation of structural parameters. The SEM and EDAX analysis also confirm that the zirconolite acts as a host material for uranium. The powder diffraction data of 3500 points for 20 = 10-80° has been analysed by GSAS (general structure analysis system) software to obtain the best fit of the observed data points. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (#15). The following unit cell parameters have been calculated: a = 12.5615(13), b= 7.2743(8), c = 11.5103(33) and β 8= 101.086(14). The calculated and observed values of the intensities, lattice parameters and density measurement show good agreement. The Rietveld analysis and GSAS based calculations for bond distance Ti-O, Ca-O, Zr-O, and O-M-O bond angles were made. The structure was refined to satisfactory completion. The Rp and Rwp were found to be 0.1583 and 0.2097 respectively. The crystal data of the title compound show that increase in U content results in expansion of the zirconolite unit cell.

  • Synthesis, characterization and structural refinement of Polycrystalline uranium substituted zirconolite
    Journal of Materials Science, 2005
    Co-Authors: O P Shrivastava, Narendra Kumar, Indu Sharma
    Abstract:

    Ceramic precursors of Zirconolite (CaZrTi2O7) family have a remarkable property of substitution on Zr4 + cationic sites. This makes them potential material for nuclear waste management in ‘synroc’ technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a Solid phase of composition CaZr0.95U0.05Ti2O7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The Polycrystalline Solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The SEM and EDAX analysis also confirm that zirconolite acts as a host material for uranium. The powder diffraction data of 3500 points between 2θ = 10–80° has been analysed by GSAS (general structure analysis system) software to obtain the best fit of the observed data points. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (#15). The following unit cell parameters have been calculated: a = 12.4883(15), b = 7.2448(5), c = 11.3973(10) and β = 100.615(9)°. The calculated and observed values of the intensities, lattice parameters and density measurement shows good agreement. The Rietveld analysis and GSAS based calculations for bond distance Ti—O, Ca—O, Zr—O, and O—M—O bond angles have been made. The structure was refined to satisfactory completion.The and Rp and Rwp are found to be 7.48 and 9.74 % respectively.

V. V. Marchenkov - One of the best experts on this subject based on the ideXlab platform.

  • precursor synthesis and magnetic properties of cd1 xfexo 0 x 0 07 Polycrystalline Solid solutions
    Journal of Alloys and Compounds, 2017
    Co-Authors: V.n. Krasilnikov, V.p. Zhukov, О.i. Gyrdasova, А.p. Tyutyunnik, Yu.А. Perevozchikova, H. W. Weber, A. Zaleski, т V Dyachkova, V. V. Marchenkov
    Abstract:

    Abstract Polycrystalline Solid solutions Cd 1- x Fe x O (0  x  ≤ 0.07) have been synthesized by the precursor method using formate of the composition Cd 1- x Fe x (HCOO) 2 ·2H 2 O as a precursor. For the production of Cd 1- x Fe x O, the precursor was annealed in air at a maximal temperature of 400 °C. At x  ≥ 0.075, an impurity CdFe 2 O 4 ferrite phase with cubic spinel structure was detected in the samples. The examination of the magnetic properties of Cd 1- x Fe x O at 5 and 300 K revealed that they are ferromagnets, whose magnetization increases with the concentration of iron both at low and room temperature reaching the maximal values in samples with х  = 0.07. In order to determine the degree of oxidation and the spin state of iron atoms, the main interatomic interactions giving rise to ferromagnetism as well as to estimate the Curie temperatures, we also performed first-principle calculations of the electronic band structure. They showed the existence of chemical bonding between adjacent iron atoms leading to the appearance of ferromagnetism by direct exchange. The value of the Curie temperature calculated by the mean field method on the basis of the first-principle calculations is 507 K, which is in reasonable agreement with the experimental value of 560 K.

  • peculiarities of epr in Polycrystalline Solid solutions zn 0 95 fe 0 05 o with different particles morphology the role of intrinsic defects in formation of magnetic properties
    Physics of the Solid State, 2017
    Co-Authors: M. A. Melkozerova, V. V. Marchenkov, O. I. Gyrdasova, A. P. Tyutyunnik, V. V. Bannikov, E. V. Zabolotskaya, Yu. A. Perevozchikova, T V Dyachkova, F. Sauerzopf
    Abstract:

    Single-phase Polycrystalline samples of Zn0.95Fe0.05O having the wurtzite structure and different morphology of particles were obtained using precursor technologies. It was found by electron spin resonance that iron enters the ZnO crystal lattice in the Fe3+ charge state. Magnetic studies revealed that the obtained samples show weak ferromagnetic properties at 300 K. A correlation between the number of oxygen vacancies and the degree of ferromagnetic ordering was found.

  • Peculiarities of EPR in Polycrystalline Solid solutions Zn_0.95Fe_0.05O with different particles morphology: The role of intrinsic defects in formation of magnetic properties
    Physics of the Solid State, 2017
    Co-Authors: M. A. Melkozerova, V. V. Marchenkov, O. I. Gyrdasova, T. V. D’yachkova, A. P. Tyutyunnik, V. V. Bannikov, E. V. Zabolotskaya, Yu. A. Perevozchikova, F. Sauerzopf, V. N. Krasil’nikov
    Abstract:

    Single-phase Polycrystalline samples of Zn_0.95Fe_0.05O having the wurtzite structure and different morphology of particles were obtained using precursor technologies. It was found by electron spin resonance that iron enters the ZnO crystal lattice in the Fe^3+ charge state. Magnetic studies revealed that the obtained samples show weak ferromagnetic properties at 300 K. A correlation between the number of oxygen vacancies and the degree of ferromagnetic ordering was found.

  • Precursor synthesis and magnetic properties of Cd1-xFexO (0 ≤ x ≤ 0.07) Polycrystalline Solid solutions
    Journal of Alloys and Compounds, 2017
    Co-Authors: V.n. Krasilnikov, V.p. Zhukov, О.i. Gyrdasova, Т.v. Dyachkova, А.p. Tyutyunnik, Yu.А. Perevozchikova, H. W. Weber, A. Zaleski, V. V. Marchenkov
    Abstract:

    Abstract Polycrystalline Solid solutions Cd 1- x Fe x O (0  x  ≤ 0.07) have been synthesized by the precursor method using formate of the composition Cd 1- x Fe x (HCOO) 2 ·2H 2 O as a precursor. For the production of Cd 1- x Fe x O, the precursor was annealed in air at a maximal temperature of 400 °C. At x  ≥ 0.075, an impurity CdFe 2 O 4 ferrite phase with cubic spinel structure was detected in the samples. The examination of the magnetic properties of Cd 1- x Fe x O at 5 and 300 K revealed that they are ferromagnets, whose magnetization increases with the concentration of iron both at low and room temperature reaching the maximal values in samples with х  = 0.07. In order to determine the degree of oxidation and the spin state of iron atoms, the main interatomic interactions giving rise to ferromagnetism as well as to estimate the Curie temperatures, we also performed first-principle calculations of the electronic band structure. They showed the existence of chemical bonding between adjacent iron atoms leading to the appearance of ferromagnetism by direct exchange. The value of the Curie temperature calculated by the mean field method on the basis of the first-principle calculations is 507 K, which is in reasonable agreement with the experimental value of 560 K.

O P Shrivastava - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis and Structure Refinement of Polycrystalline Solid Solution: Na1 + xZr2 − xSbxP3O12 (x = 0.1)
    Journal of Chemical Crystallography, 2007
    Co-Authors: O P Shrivastava, Rashmi Chourasia
    Abstract:

    The Solid solution of Na1 + x Zr2 − x Sb x P3O12 (x = 0.1) was prepared at 1,000 °C by ceramic route. The ceramic material belonging to sodium zirconium phosphate (hereafter NZP) family crystallizes in space group R-3c with unit cell parameters: a = b = 8.77283(16) A, c = 22.8375(7) A, α = β = 90.0° γ = 120.0° and Z = 6. The structure of the title phase has been determined by Rietveld refinement of the powder diffraction data on GSAS software. The refinement converges to a satisfactory structure fit with R p = 0.0764, R wp = 0.1099 and RF 2 = 0.0450. The interatomic distances and bond angles are in good agreement with their standard values. The particle size along prominent reflecting planes ranges between 13 and 50 nm. The polyhedral (ZrO6 and PO4 and NaO8) distortions and valence calculations from bond strength data are also reported. The investigations show that the Sb+3 cation occupies the zirconium (AVI) site of NZP structural framework and resultant charge compensation takes place through partial occupation of M2 site by Na+ ions. Synthesis and Structure Refinement of Polycrystalline Solid Solution: Na1 + x Zr 2 −  x Sb x P 3 O 12 ( x  = 0.1) O. P. Shrivastava and Rashmi Chourasia Antimony enters crystallochemically in the framework of nano ceramic sodium zirconium phosphate at the Zr site of the ZrO6 octahedra which are inter linked by PO4 tetrahedra through corner sharing of the vertical columns.

  • Synthesis, characterization and structural refinement of Polycrystalline uranium substituted zirconolite
    Journal of Materials Science, 2005
    Co-Authors: O P Shrivastava, Narendra Kumar, Indu Sharma
    Abstract:

    Ceramic precursors of Zirconolite (CaZrTi2O7) family have a remarkable property of substitution on Zr4 + cationic sites. This makes them potential material for nuclear waste management in ‘synroc’ technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a Solid phase of composition CaZr0.95U0.05Ti2O7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The Polycrystalline Solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The SEM and EDAX analysis also confirm that zirconolite acts as a host material for uranium. The powder diffraction data of 3500 points between 2θ = 10–80° has been analysed by GSAS (general structure analysis system) software to obtain the best fit of the observed data points. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (#15). The following unit cell parameters have been calculated: a = 12.4883(15), b = 7.2448(5), c = 11.3973(10) and β = 100.615(9)°. The calculated and observed values of the intensities, lattice parameters and density measurement shows good agreement. The Rietveld analysis and GSAS based calculations for bond distance Ti—O, Ca—O, Zr—O, and O—M—O bond angles have been made. The structure was refined to satisfactory completion.The and Rp and Rwp are found to be 7.48 and 9.74 % respectively.

Narendra Kumar - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis, characterization and structural refinement of Polycrystalline uranium substituted zirconolite CaZr0.9U0.1Ti2O7
    Radiochimica Acta, 2006
    Co-Authors: Omprakash Shrivastava, Narendra Kumar, Indu Sharma
    Abstract:

    Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution on Zr 4+ cationic sites. This makes them a potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a Solid phase of composition CaZr 0.9 U 0.1 Ti 2 O 7 was synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium, respectively. Solid-state synthesis was carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The Polycrystalline Solid phase was characterized by its typical powder diffraction pattern. Step analysis data were used for ab initio calculation of structural parameters. The SEM and EDAX analysis also confirm that the zirconolite acts as a host material for uranium. The powder diffraction data of 3500 points for 20 = 10-80° has been analysed by GSAS (general structure analysis system) software to obtain the best fit of the observed data points. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (#15). The following unit cell parameters have been calculated: a = 12.5615(13), b= 7.2743(8), c = 11.5103(33) and β 8= 101.086(14). The calculated and observed values of the intensities, lattice parameters and density measurement show good agreement. The Rietveld analysis and GSAS based calculations for bond distance Ti-O, Ca-O, Zr-O, and O-M-O bond angles were made. The structure was refined to satisfactory completion. The Rp and Rwp were found to be 0.1583 and 0.2097 respectively. The crystal data of the title compound show that increase in U content results in expansion of the zirconolite unit cell.

  • Synthesis, characterization and structural refinement of Polycrystalline uranium substituted zirconolite
    Journal of Materials Science, 2005
    Co-Authors: O P Shrivastava, Narendra Kumar, Indu Sharma
    Abstract:

    Ceramic precursors of Zirconolite (CaZrTi2O7) family have a remarkable property of substitution on Zr4 + cationic sites. This makes them potential material for nuclear waste management in ‘synroc’ technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a Solid phase of composition CaZr0.95U0.05Ti2O7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The Polycrystalline Solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The SEM and EDAX analysis also confirm that zirconolite acts as a host material for uranium. The powder diffraction data of 3500 points between 2θ = 10–80° has been analysed by GSAS (general structure analysis system) software to obtain the best fit of the observed data points. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (#15). The following unit cell parameters have been calculated: a = 12.4883(15), b = 7.2448(5), c = 11.3973(10) and β = 100.615(9)°. The calculated and observed values of the intensities, lattice parameters and density measurement shows good agreement. The Rietveld analysis and GSAS based calculations for bond distance Ti—O, Ca—O, Zr—O, and O—M—O bond angles have been made. The structure was refined to satisfactory completion.The and Rp and Rwp are found to be 7.48 and 9.74 % respectively.

V.n. Krasilnikov - One of the best experts on this subject based on the ideXlab platform.

  • precursor synthesis and magnetic properties of cd1 xfexo 0 x 0 07 Polycrystalline Solid solutions
    Journal of Alloys and Compounds, 2017
    Co-Authors: V.n. Krasilnikov, V.p. Zhukov, О.i. Gyrdasova, А.p. Tyutyunnik, Yu.А. Perevozchikova, H. W. Weber, A. Zaleski, т V Dyachkova, V. V. Marchenkov
    Abstract:

    Abstract Polycrystalline Solid solutions Cd 1- x Fe x O (0  x  ≤ 0.07) have been synthesized by the precursor method using formate of the composition Cd 1- x Fe x (HCOO) 2 ·2H 2 O as a precursor. For the production of Cd 1- x Fe x O, the precursor was annealed in air at a maximal temperature of 400 °C. At x  ≥ 0.075, an impurity CdFe 2 O 4 ferrite phase with cubic spinel structure was detected in the samples. The examination of the magnetic properties of Cd 1- x Fe x O at 5 and 300 K revealed that they are ferromagnets, whose magnetization increases with the concentration of iron both at low and room temperature reaching the maximal values in samples with х  = 0.07. In order to determine the degree of oxidation and the spin state of iron atoms, the main interatomic interactions giving rise to ferromagnetism as well as to estimate the Curie temperatures, we also performed first-principle calculations of the electronic band structure. They showed the existence of chemical bonding between adjacent iron atoms leading to the appearance of ferromagnetism by direct exchange. The value of the Curie temperature calculated by the mean field method on the basis of the first-principle calculations is 507 K, which is in reasonable agreement with the experimental value of 560 K.

  • Precursor synthesis and magnetic properties of Cd1-xFexO (0 ≤ x ≤ 0.07) Polycrystalline Solid solutions
    Journal of Alloys and Compounds, 2017
    Co-Authors: V.n. Krasilnikov, V.p. Zhukov, О.i. Gyrdasova, Т.v. Dyachkova, А.p. Tyutyunnik, Yu.А. Perevozchikova, H. W. Weber, A. Zaleski, V. V. Marchenkov
    Abstract:

    Abstract Polycrystalline Solid solutions Cd 1- x Fe x O (0  x  ≤ 0.07) have been synthesized by the precursor method using formate of the composition Cd 1- x Fe x (HCOO) 2 ·2H 2 O as a precursor. For the production of Cd 1- x Fe x O, the precursor was annealed in air at a maximal temperature of 400 °C. At x  ≥ 0.075, an impurity CdFe 2 O 4 ferrite phase with cubic spinel structure was detected in the samples. The examination of the magnetic properties of Cd 1- x Fe x O at 5 and 300 K revealed that they are ferromagnets, whose magnetization increases with the concentration of iron both at low and room temperature reaching the maximal values in samples with х  = 0.07. In order to determine the degree of oxidation and the spin state of iron atoms, the main interatomic interactions giving rise to ferromagnetism as well as to estimate the Curie temperatures, we also performed first-principle calculations of the electronic band structure. They showed the existence of chemical bonding between adjacent iron atoms leading to the appearance of ferromagnetism by direct exchange. The value of the Curie temperature calculated by the mean field method on the basis of the first-principle calculations is 507 K, which is in reasonable agreement with the experimental value of 560 K.