Coexistence of Weak Ferromagnetism and Paramagnetism in T’-Pr2-xCexCuO4+α-δ Nanoparticles

2020 ◽  
Vol 855 ◽  
pp. 134-139
Author(s):  
Putu Eka Dharma Putra ◽  
Resky Irfanita ◽  
Bambang Triono ◽  
Malik Anjelh Baqiya ◽  
Darminto
Keyword(s):  
Normal State ◽  
Maximum Entropy Method ◽  
Weak Ferromagnetism ◽  
Entropy Method ◽  
X Ray Diffraction ◽  
Calcination Process ◽  
Reduction Annealing ◽  
Vibration Sample Magnetometer ◽  
Weak Ferromagnetic ◽  
Paramagnetic Properties

The coexistence of ferromagnetism and paramagnetism of T’-Pr2-xCexCuO4+α-δ (T’-PCCO) nanoparticles with x = 0, and 0.10 have been studied intensively in the normal state. All samples were synthesized by a chemically dissolved method using HNO3 as a dissolving agent. The calcination process was performed at 1000°C for 15 h in air and followed by reduction annealing at 700°C in argon atmosphere for 10 h. All samples were first characterized by an x-ray diffraction (XRD) measureemnts followed by Rietveld and Maximum Entropy Method (MEM) analyseis. The result confirms the Ce-dependence and reduction annealing effect on the electron density at around the Cu site. The magnetic characterization was performed by using vibration sample magnetometer (VSM) indicating weak ferromagnetic properties at x = 0 and dominant paramagnetic properties at x = 0.10 at room temperature. Moreover, the weak ferromagnetic feature seems to remain after the annealing process. This signifies the coexist of weak ferromagnetism and paramagnetism at the normal state due to a number of oxygen vacancies in the crystal structure.

A model-independent maximum-entropy method for the inversion of small-angle X-ray diffraction patterns

1999 ◽  
Vol 32 (6) ◽  
pp. 1069-1083 ◽  
Author(s):  
J. A. Elliott ◽  
S. Hanna
Keyword(s):  
Maximum Entropy ◽  
Small Angle ◽  
Disordered Systems ◽  
Maximum Entropy Method ◽  
Structural Model ◽  
Entropy Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Model Independent ◽  
Diffraction Patterns

A model-independent maximum-entropy method is presented which will produce a structural model from small-angle X-ray diffraction data of disordered systems using no other prior information. In this respect, it differs from conventional maximum-entropy methods which assume the form of scattering entitiesa priori. The method is demonstrated using a number of different simulated diffraction patterns, and applied to real data obtained from perfluorinated ionomer membranes, in particular Nafion™, and a liquid crystalline copolymer of 1,4-oxybenzoate and 2,6-oxynaphthoate (B–N).

An Evaluation of Deconvolution Techniques in X-ray Profile Broadening Analysis and the Application of the Maximum Entropy Method to Alumina Data

1994 ◽  
Vol 38 ◽  
pp. 387-395 ◽  
Author(s):  
Walter Kalceff ◽  
Nicholas Armstrong ◽  
James P. Cline
Keyword(s):  
Maximum Entropy ◽  
Maximum Entropy Method ◽  
Profile Analysis ◽  
Domain Size ◽  
Entropy Method ◽  
X Ray Diffraction ◽  
Profile Function ◽  
Diffraction Profile ◽  
X Ray ◽  
Deconvolution Techniques

Abstract This paper reviews several procedures for the removal of instrumental contributions from measured x-ray diffraction profiles, including: direct convolution, unconstrained and constrained deconvolution, an iterative technique, and a maximum entropy method (MEM) which we have adapted to x-ray diffraction profile analysis. Decorevolutions using the maximum entropy approach were found to be the most robust with simulated profiles which included Poisson-distributed noise and uncertainties in the instrument profile function (IPF). The MEM procedure is illustrated by application to the analysis for domain size and microstrain carried out on the four calcined α-alumina candidate materials for Standard Reference Material (SRM) 676 (a quantitative analysis standard for I/Ic determinations), along with the certified material. Williamson-Hall plots of these data were problematic with respect to interpretation of the microstrain, indicating that the line profile standard, SRM 660 (LaB6), exhibits a small amount of strain broadening, particularly at high 2θ angle. The domain sizes for all but one of the test materials were much smaller than the crystallite (particle) size; indicating the presence of low angle grain boundaries.

Charge density study with the Maximum Entropy Method on model data of silicon. A search for non-nuclear attractors

1996 ◽  
Vol 74 (6) ◽  
pp. 1054-1058 ◽  
Author(s):  
R.Y. de Vries ◽  
W.J. Briels ◽  
D. Fell ◽  
G. te Velde ◽  
E.J. Baerends
Keyword(s):  
Charge Density ◽  
Maximum Entropy ◽  
Density Functional ◽  
Maximum Entropy Method ◽  
Entropy Method ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Structure Factors ◽  
The Density Functional Theory ◽  
Structure Calculations

In 1990 Sakata and Sato applied the maximum entropy method (MEM) to a set of structure factors measured earlier by Saka and Kato with the Pendellösung method. They found the presence of non-nuclear attractors, i.e., maxima in the density between two bonded atoms. We applied the MEM to a limited set of Fourier data calculated from a known electron density distribution (EDD) of silicon. The EDD of silicon was calculated with the program ADF-BAND. This program performs electronic structure calculations, including periodicity, based on the density functional theory of Hohenberg and Kohn. No non-nuclear attractor between two bonded silicon atoms was observed in this density. Structure factors were calculated from this density and the same set of structure factors that was measured by Saka and Kato was used in the MEM analysis. The EDD obtained with the MEM shows the same non-nuclear attractors that were later obtained by Sakata and Sato. This means that the non-nuclear attractors in silicon are really an artefact of the MEM. Key words: Maximum Entropy Method, non-nuclear attractors, charge density. X-ray diffraction.

scholarly journals Structural and Charge Density Properties of Manganese Sulfide

2019 ◽  
Vol 9 (2S2) ◽  
pp. 313-315
Keyword(s):  
Charge Density ◽  
Maximum Entropy Method ◽  
Manganese Sulfide ◽  
Entropy Method ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Structure Factors ◽  
Density Analysis ◽  
Distribution Studies ◽  
Profile Refinement

Single phased Manganese Sulfide was analyzed by powder X-ray diffraction (PXRD) data sets with cubic structure. The simulated XRD data sets were used to analyze the structure of manganese sulfide. The powder profile refinements were done by Rietveld profile refinement technique. The refinement results were subjected to analyze the charge density analysis using structure factors. The chemical bonding nature between Mn and S were analyzed by charge density distribution studies through maximum entropy method. From MEM analsysis, it found that the bonding between Mn and S atoms is ionic in nature.

scholarly journals Location of Cu2+in CHA zeolite investigated by X-ray diffraction using the Rietveld/maximum entropy method

IUCrJ ◽  
2014 ◽  
Vol 1 (6) ◽  
pp. 382-386 ◽  
Author(s):  
Casper Welzel Andersen ◽  
Martin Bremholm ◽  
Peter Nicolai Ravnborg Vennestrøm ◽  
Anders Bank Blichfeld ◽  
Lars Fahl Lundegaard ◽  
...  
Keyword(s):  
Maximum Entropy ◽  
Density Functional ◽  
Maximum Entropy Method ◽  
Entropy Method ◽  
Membered Ring ◽  
Zeolite Catalysts ◽  
Structural Description ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalytically Active

Accurate structural models of reaction centres in zeolite catalysts are a prerequisite for mechanistic studies and further improvements to the catalytic performance. The Rietveld/maximum entropy method is applied to synchrotron powder X-ray diffraction data on fully dehydrated CHA-type zeolites with and without loading of catalytically active Cu2+for the selective catalytic reduction of NOxwith NH3. The method identifies the known Cu2+sites in the six-membered ring and a not previously observed site in the eight-membered ring. The sum of the refined Cu occupancies for these two sites matches the chemical analysis and thus all the Cu is accounted for. It is furthermore shown that approximately 80% of the Cu2+is located in the new 8-ring site for an industrially relevant CHA zeolite with Si/Al = 15.5 and Cu/Al = 0.45. Density functional theory calculations are used to corroborate the positions and identity of the two Cu sites, leading to the most complete structural description of dehydrated silicoaluminate CHA loaded with catalytically active Cu2+cations.

Maximum Entropy Method Charge Density Distributions of Novel Thermoelectric Clathrates

1999 ◽  
Vol 590 ◽  
Author(s):  
B. Iversen ◽  
A. Bentien ◽  
A. Palmqvist ◽  
D. Bryan ◽  
S. Latturner ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Charge Density ◽  
Maximum Entropy ◽  
Maximum Entropy Method ◽  
Mixed Valence ◽  
Entropy Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Distributions ◽  
Positively Charged

ABSTRACTRecently materials with promising thermoelectric properties were discovered among the clathrates. Transport data has indicated that these materials have some of the characteristics of a good thermoelectric, namely a low thermal conductivity and a high electrical conductivity. Based on synchrotron powder and conventional single crystal x-ray diffraction data we have determined the charge density distribution in Sr8Ga16Ge3O using the Maximum Entropy Method. The MEM density shows clear evidence of guest atom rattling, and this contributes to the reduction of the thermal conductivity. Analysis of the charge distribution reveals that Sr8Ga16Ge30 contains mixed valence alkaline earth guest atoms. The Sr atoms in the small cavities are, as expected, doubly positively charged, whereas the Sr atoms in the large cavities appear negatively charged. The MEM density furthermore suggests that the Ga and Ge atoms may not be randomly disordered on the framework sites as found in the conventional leastsquares refinements.

Effect of Pb Substitution on Superconducting and Normal State Electrical Properties of Bi2Sr2CaCu2O8+σ Nanopowders

2015 ◽  
Vol 827 ◽  
pp. 235-239
Author(s):  
Fahmi Astuti ◽  
Malik Anjelh Baqiya ◽  
Darminto
Keyword(s):  
Normal State ◽  
Quantum Interference ◽  
Superconducting Quantum Interference Device ◽  
X Ray Diffraction ◽  
Bulk Superconductor ◽  
Calcination Process ◽  
Free Sample ◽  
Short Period ◽  
Pb Substitution ◽  
Lower Resistivity

Abstract.The powders of Bi2-xPbxSr2CaCu2O8+δ(x=0; 0.4) superconductor have been prepared by using dissolved method followed by short period of sintering and calcination process . The purpose of this research is to study about the Pb doped effect to the properties of BSCCO nanopowders especially in the electric and superconducting properties. Based on the previous result, BSCCO nanopowders have ferromagnetic properties at the room temperature. This characteristic is not appeared in bulk superconductor. The 2212 phase of Bi-based system has been formed and observed by using X-ray diffraction (XRD) measurement. The superconducting quantum interference device (SQUID) observation showed that the Bi2-xPbxSr2CaCu2O8+δ(x=0; 0.4) samples exhibited diamagnetic behaviour at the critical temperature, Tc=76 K and 78 K. The sample with partial Pb substitution exhibited stronger permanency to the external magnetic field indicating presence of flux pinning. The four point probe (FPP) measurement showed that the sample partially doped with Pb has lower resistivity (more metallic) than the Pb-free sample in the normal state.

Sign in / Sign up

Export Citation Format

Share Document