Neutron Diffraction Study on Ce-Doped Nickel Ferrite Nanoparticles

2020 ◽  
Vol 855 ◽  
pp. 22-27
Author(s):  
Engkir Sukirman ◽  
Yunasfi ◽  
Andon Insani ◽  
Wisnu Ari Adi
Keyword(s):  
Neutron Diffraction ◽  
Mole Fraction ◽  
Rietveld Method ◽  
Magnetic Moments ◽  
Site Occupancy ◽  
Neutron Diffraction Pattern ◽  
High Energy ◽  
Neutron Diffraction Study ◽  
Cubic Symmetry ◽  
A Site

The NiCexFe2-xO4 polycrystalline spinel compound with composition x = 0.005, 0.010, 0.015, and 0.02 was synthesized by the solid reaction method using the high energy milling (HEM) apparatus. Measurement of the neutron diffraction patterns is carried out at room temperature using a high resolution powder neutron diffractometer (HRPD), wavelength λ = 1.8213 Å. The measured neutron diffraction data were analyzed by the Rietveld method utilizing the FullProf analysis code. The results of the neutron diffraction pattern refinement revealed that the sample has a cubic symmetry, the Fd-3m space group, mixed inverse spinel structure, A-site occupied by cation Fe3+, Ni2+, dan Ce3+. Whereas the B-site is only occupied by Fe3+ and Ni2+. The mole fraction of Fe3+ at the B-site is greater than the Fe3+ mole fraction at the A-site, whereas the mole fraction of Ni2+ at the B-site is smaller than the mole fraction of Ni2+ at the B-site. As a result of Ce3+ doping, oxygen position parameters increase, magnetic moments on B-site, and the net magnetic moments decrease. Ni2+ concentrations at the A-site and the B-site were not affected by the amount of Ce3+ substitutions. Without substitution and after Ce3+ substitution, the O-site occupancy factor is still oxygen deficient.

Structural Characterization of Ceria–zirconia Powder Catalysts Prepared by High-energy Mechanical Milling: A Neutron Diffraction Study

2000 ◽  
Vol 15 (7) ◽  
pp. 1538-1545 ◽  
Author(s):  
S. Enzo ◽  
F. Delogu ◽  
R. Frattini ◽  
A. Primavera ◽  
A. Trovarelli
Keyword(s):  
Neutron Diffraction ◽  
Mechanical Milling ◽  
Rietveld Method ◽  
Axial Ratio ◽  
High Energy ◽  
Neutron Diffraction Study ◽  
Stable Form ◽  
Cell Parameters ◽  
Internal Deformation

Neutron diffraction measurements were carried out on samples of CeO2–ZrO2 powder catalysts prepared by high-energy mechanical milling. The formation of solid solution was evidenced across the entire composition range examined. Quantitative phase evaluation by the Rietveld method indicated formation of tetragonal structure for low CeO2 content, whereas cubic solid solutions were the stable form at high CeO2 loading. In addition, a pseudocubic or tetragonal t″ cell with axial ratio of unity and with internal deformation of the oxygen sublattice was observed at intermediate composition (50 mol% CeO2). Thermal annealing up to 1000 °C showed expansion of the unit cell parameters; an increase in the degree of tetragonality at the expense of cubic and monoclinic phase was observed for composition CexZr1−xO2 (x < 0.5).

Powder Neutron Diffraction Study of Pyrolusite, β-MnO2

1993 ◽  
Vol 46 (6) ◽  
pp. 939 ◽  
Author(s):  
AA Bolzan ◽  
C Fong ◽  
BJ Kennedy ◽  
CJ Howard
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Diffraction Pattern ◽  
Rietveld Method ◽  
Neutron Diffraction Pattern ◽  
Neutron Diffraction Study ◽  
Thermal Parameters ◽  
Powder Neutron Diffraction ◽  
Position Parameter ◽  
Thermal Vibrations

The powder neutron diffraction pattern of pyrolusite, β-MnO2 [P42/mnm, No. 136, a = 4.4041(1), c = 2.8765(1)Ǻ], has been refined by the Rietveld method to give values for both the oxygen position parameter u=0.3046(1) and the anisotropic thermal parameters. The data confirm the MnO6 octahedra to be elongated with two long [1.894(1)Ǻ] and four short [1.882(2)Ǻ] Mn-O bond distances. The effect of the stereochemistry on the thermal vibrations is discussed.

X-ray powder diffraction study of K2MSiO4, M=Mg, Zn, Co, Cd

1996 ◽  
Vol 11 (1) ◽  
pp. 51-55 ◽  
Author(s):  
W. A. Dollase
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Site Occupancy ◽  
Cubic Phase ◽  
Variable Degree ◽  
Cubic Symmetry ◽  
X Ray ◽  
Constrained Model ◽  
Diffraction Patterns

The title materials are stuffed cristobalites possessing moderate to extreme pseudosymmetry. On the bases of their X-ray powder diffraction patterns, the Mg, Zn, and Cd compounds had been previously reported as cubic and, more recently, the Zn phase as orthorhombic. Newly measured X-ray powder diffraction data demonstrate that all (including the hitherto unknown Co analog) have the Pca21 structure of Na2BeSiO4 at room temperature, but with a widely variable degree of cubic pseudosymmetry. Observed X-ray diffraction data are in good agreement with those calculated by the Rietveld method using a constrained model with Pca21 M2+/Si site occupancy and pseudocentrosymmetric Pcab atom locations. For the most nearly cubic phase, the Cd compound, there is too little deviation in the pattern from cubic symmetry to support atom coordinate refinement even with the constrained model. In these derivatives of the stuffed cristobalite structure family, M2+ and Si atoms form an ordered tetrahedral array which avoids M2+–O–M2+ connections. Potassium atoms fill all of the intervening large cavity sites.

Alternative materials for radiovoltaics

2017 ◽  
Author(s):  
◽  
Bradley R. Nullmeyer
Keyword(s):  
Monte Carlo ◽  
Neutron Diffraction ◽  
Diffraction Study ◽  
Pair Correlation ◽  
High Energy ◽  
Neutron Diffraction Study ◽  
Beta Radiation ◽  
Reverse Monte Carlo ◽  
Tritium Production ◽  
Alternative Materials

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This work explores alternative materials for the improvement of radiovoltaic devices. First, lithium fluoride is explored as an effective material for generating and retaining tritium radionuclides for use in radiovoltaics. This development aims to solve a decades-old problem of inadequate tritium hosts, which have been consistently limited in their ability to retain the radioisotope and effectively deliver energy to transducing semiconductors. This new method of tritium production and retention offers new possibilities for use of what has been deemed the safest radioisotope, and offers a simple, rapid production process, which can greatly reduce cumbersome isotope loading processes associated with existing methods of fabrication for devices reliant on tritium or other radioisotopes. The primary focus of this work is the exploration of molten selenium-sulfur as a radiation-resistant semiconductor for radiovoltaic devices. Radiovoltaics have thus far been unable to utilize high energy alpha and beta radiation due to rapid performance degradation imposed by radiation damage. This work includes the exhibition of long-term power output from an alphavoltaic device fueled by 210Po. The 57+ day lifetime of this device is in great contrast to reports of conventional semiconductors, which have consistently exhibited short lifetimes. Moreover, this report details a neutron diffraction study of irradiated Se-S material, which indicates strong radiation-resistance in the liquid phase. With liquid selenium established as a promising material for radiovoltaics, this work also presents a neutron diffraction study on the material's atomic structure, which has been the subject of dispute in published literature. The neutron diffraction study is accompanied by Reverse Monte Carlo analysis, resulting in reliable conclusions regarding the overall structure near the melting point. The analysis of Reverse Monte Carlo models in comparison to experimental data identifies in the pair correlation function a key indicator of 3-fold coordinated defects which disrupt the liquid selenium structure under extreme conditions.

The crystal structure of phlogopite by neutron diffraction

1974 ◽  
Vol 39 (308) ◽  
pp. 850-856 ◽  
Author(s):  
J. H. Rayner
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Study ◽  
Three Dimensional ◽  
Site Occupancy ◽  
Fluorine Content ◽  
Neutron Diffraction Study ◽  
Hydroxyl Group ◽  
Octahedral Sites

SummaryThe positions of all the atoms including hydrogen have been found by a partial three-dimensional single-crystal neutron-diffraction study in which about one-third of the reflections in the reciprocal sphere to 1·5 Å were measured. The hydroxyl group is perpendicular to the plane of the silicate sheets. The fluorine content of this phlogopite is enough to occupy 25 % of the (OH, F) sites. Site occupancy refinement suggests that there is a small deficiency of hydrogen at the remaining sites and that the two crystallographically different octahedral sites are fully occupied by the same proportions of Mg, Ti, Fe, and Ca.

Anharmonicity and disorder in simple and complex perovskites: a high energy synchrotron and hot neutron diffraction study

2000 ◽  
Vol 12 (39) ◽  
pp. 8411-8425 ◽  
Author(s):  
Jean-Michel Kiat ◽  
Gianguido Baldinozzi ◽  
Muriel Dunlop ◽  
Charlotte Malibert ◽  
Brahim Dkhil ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
High Energy ◽  
Neutron Diffraction Study ◽  
Complex Perovskites

A neutron diffraction study of the deuterium site occupancy in Nd/sub 5/Fe/sub 17/D/sub 15.5/

2001 ◽  
Vol 37 (4) ◽  
pp. 2172-2175 ◽  
Author(s):  
Z. Chu ◽  
W.B. Yelon ◽  
R.K. Murakami ◽  
P.S.M. da Silva ◽  
V. Villas-Boas ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Site Occupancy ◽  
Neutron Diffraction Study

First accurate location of two proton sites in tourmaline: A single-crystal neutron diffraction study of oxy-dravite

2014 ◽  
Vol 78 (3) ◽  
pp. 681-692 ◽  
Author(s):  
G. D. Gatta ◽  
F. Bosi ◽  
G. J. McIntyre ◽  
H. Skogby
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Study ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Bond Distance ◽  
Neutron Diffraction Study ◽  
Fold Axis ◽  
Absorption Bands ◽  
First Time

AbstractA single-crystal neutron diffraction study of oxy-dravite from Osarara (Narok district, Kenya) was performed. Intensity data were collected in Laue geometry at 10 K and anisotropic-structure refinement was undertaken. For the first time, two independent H sites were refined unambiguously for a mineral belonging to the tourmaline supergroup and located at 0.26, 0.13, 0.38 (labelled as H3, site occupancy ∼98%) and at 0, 0, 0.9 (labelled as H1, site occupancy ∼25%). The H-bonding scheme can thus be defined as follows: (1) the O at the O3 site acts as a ‘donor’ and the O at the O5 site as ‘acceptor’, the refined O3–H3 bond distance is 0.972(2) Å (and 0.9946 Å corrected for “riding motion”), H3⋯O5 = 2.263(2) Å, O3⋯O5 = 3.179(1) Å and O3–H3⋯O5 = 156.6(1)°; (2) the oxygen at the O1 site acts as a ‘donor’ and the O atoms at O4 and O5 as ‘acceptors’, the refined O1–H1 bond distance is 0.958(8) Å (and 0.9833 Å corrected for “riding motion”), H1⋯O4 = 2.858(6) Å, O1⋯O4 = 3.378(1) Å and O1–H1⋯O4 = 115.12(1)°, whereas H1⋯O5 = 2.886(6) Å, O1⋯O5 = 3.444(1) Å and O1–H1⋯O5 = 118.23(1)°. A further test refinement was performed with the H1 site out of the three-fold axis (at 0.02, 0.01, 0.90); this leads to O1–H1 = 0.995(8) Å (and 1.0112 Å corrected for “riding motion”), H1⋯O4 = 2.747(6) Å and O1–H1⋯O4 = 121.7(4)°, whereas H1⋯O5 = 2.654(9) Å and O1–H1⋯O5 = 136.5(6)°. Bond-valence analysis shows that the H-bonding strength involving O3 is stronger than that involving O1: ∼0.11 and <0.05 valence units, respectively.The refined angle between the O3–H3 vector and [0001] is 3.40(9)°. Such a small angle is in line with a pleochroic scheme for the OH-stretching absorption bands measured by infrared spectroscopy.

Study of the Sintering of Mixtures Al2O3-Nb2O5 and Y2O3-Nb2O5

2012 ◽  
Vol 727-728 ◽  
pp. 799-803 ◽  
Author(s):  
Ricardo F. Cabral ◽  
Marcelo Henrique Prado da Silva ◽  
Jose B. de Campos ◽  
Eduardo Sousa Lima
Keyword(s):  
Weight Loss ◽  
Mass Loss ◽  
Mole Fraction ◽  
Ball Mill ◽  
Rietveld Method ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
High Energy Milling

Al2O3-Nb2O5 has been widely explored as one of the most used material for sintering mixing in the literature, due to its excellent hardness properties, used in armor. In this study, Al2O3-Nb2O5 and Y2O3-Nb2O5 powders were prepared, with 50% in mole fraction of each oxide. The mixtures were subjected to high energy milling in an eccentric ball mill for 3 h, dried and sieved in a sieve vibrator. The green bodies were compacted at 70 MPa and sintered from 1250 to 1650 °C for 3 h, at 100 °C steps. The materials were characterized by quantitative X-Ray diffraction (XRD) using Rietveld method and by mass loss. The Al2O3-Nb2O5 mixtures experienced a weight loss of 84% at sintering temperatures of 1550 and 1650 °C.

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