Transcript Introduction to the difraction analysis and SANS method

Introduction to the
difraction analysis and
SANS method
Students:
Dana-Maria GHITA (Univ. of Craiova, Romania)
Nicoleta-Madalina GIURGEA (Univ. of Bucharest, Romania)
Andreea OPREA (Univ. of Bucharest, Romania)
Claudia-Teodora TEODORESCU-SOARE (Univ. of Jassy, Romania)
Project Coordinators:
Dr. M. L. CRAUS (FLNP)
Dr. A. I. KUKLIN (FLNP)
JINR Summer Student Practice 5-25 July 2010
Part 1:
Corelations between structure
and transport caracteristics
of manganites with Cr impurities
(La0.54Ho0.11Sr0.35)(Mn1-xCrx)O3
Outline
Work done within the Project

Overview

Results

Conclusions
Work Done Within the Project
Manganite samples with the general structure
La0.54Ho0.11Sr0.35Mn1-xCrxO3 have been studied
using FullProf Suite code for existing data at
(x = 0.05; 0.10; 0.15; 0.20).
The goal of investigation was to estimate
qualitatively :
(1) the variation of the lattice constant values
in terms of Cr impurity concentration
(2) microstrain and crystallite average size
dependence on the Cr concentration.
Outline

Work done within the Project
Overview

Results

Conclusions
Overview
The samples:
La0.54Ho0.11Sr0.35Mn1-xCrxO3 manganites were prepared by sol-gel
method using oxides and acetates and sintered in air at 1200 C for
15 h.
It is known:
The samples show perovskite phases, with orthorhombic structure
(Space Group – P n m a). ABO3 perovskito-manganites determine
the charge transport behavior and complex magnetic and
crystalline structures.
X-ray data for samples (with different Cr concentrations) mentioned
in our report was obtained with Hubber-Guinier diffractometer by
using Cr Kα1 radiation and was handled using FullProf Suite code.
Unit cell of manganite
La0.54Ho0.11Sr0.35Mn1-xCrxO3
Features:
- Distorted Perovskite
- Orthorhombic space
group: Pnma #62
- Primitive lattice (P)
- Glide plane (n)
perpendicular to a axis
- Mirror plane (m)
perpendicular to b axis
- Glide plane (a)
perpendicular to c axis
FullProf Main Features
The program has been mainly developed for Rietveld analysis (structure
profile refinement) of neutron (nuclear and magnetic scattering) or Xray powder diffraction data collected at constant or variable step in
scattering angle 2θ
• X-ray diffraction data: laboratory and synchrotron sources.
• Neutron diffraction data: Constant Wavelength (CW) and Time of Flight (TOF).
• The scattering variable may be 2θ in degrees, TOF in microseconds and Energy in
KeV.
• Background: fixed, refinable, adaptable, or with Fourier filtering.
• Choice of peak shape for each phase: Gaussian, Lorentzian, modified Lorentzians,
pseudo-Voigt, Pearson-VII, Thompson-Cox-Hastings (TCH) pseudo-Voigt,
numerical, split pseudo-Voigt, convolution of a double exponential with a TCH
pseudo-Voigt for TOF.
• Multi-phase (up to 16 phases).
• Absorption correction for a different geometries. Micro-absorption correction
for Bragg-Brentano set-up.
free program http://www.ill.eu/sites/fullprof/
FullProf Main Features
• Choice between automatic generation of hkl and/or symmetry operators and file
given by user.
• Magnetic structure refinement (crystallographic and spherical representation of
the magnetic moments).
• hkl-dependence of the position shifts of Bragg reflections for special kind of
defects.
• Profile Matching. The full profile can be adjusted without prior knowledge of the
structure (needs only good starting cell and profile parameters).
• Quantitative analysis without need of structure factor calculations.
• Chemical (distances and angles) and magnetic (magnetic moments) slack
constraints. They can be generated automatically by the program.
• The instrumental resolution function (Voigt function) may be supplied in a file. A
microstructural analysis is then performed.
• Neutron (or X-rays) powder patterns can be mixed with integrated intensities of
X-rays (or neutron) from single crystal or powder data.
• Full Multi-pattern capabilities. The user may mix several powder diffraction
patterns (eventually heterogeneous: X-rays, TOF neutrons, etc.) with total control
of the weighting scheme.
Outline

Work done within the Project

Overview
Results

Conclusions
Observed and calculated difractograms of
La0.54Ho0.11Sr0.35Mn0.95Cr0.05O3 (FullProf method)
Observed and calculated difractograms of
La0.54Ho0.11Sr0.35Mn0.90Cr0.10O3 (FullProf method)
Observed and calculated difractograms of
La0.54Ho0.11Sr0.35Mn0.85Cr0.15O3 (FullProf method)
Observed and calculated difractograms of
La0.54Ho0.11Sr0.35Mn0.80Cr0.20O3 (FullProf method)
Variation of the lattice constants and the unit
cell volume (a,b,c,V) vs. Cr concentration x
x
a(Å)
b(Å)
c(Å)
V(Å3)
0.05
5.4229
7.6628
5.4038
224.553
0.10
5.3786
7.5831
5.3924
219.937
0.15
5.3793
7.5922
5.3865
219.989
0.20
5.3767
7.5946
5.3823
219.780
Variation of the microstrain Ɛ and of the
apparent size of the crystallite vs. Cr
concentration x
x
Ɛ
D (Å)
0.05
0.0289579
467.86
0.10
0.0317542
423.55
0.15
0.0265669
712.69
0.20
0.0222624
601.97
Outline

Work done within the Project

Overview

Results
Conclusions
Conclusions to Part 1


Lattice constants a and c decrease
monotonically, while b and unit cell volume V
vary non-monotonically with the Cr (chrome)
concentration.
The microstrain shows a maximum, while the
average size of crystallites shows nonmonotonic variation with Cr concentration .
Part 2 : SANS - Introduction
•Small angle neuton scattering is a method of analisys used in
research for the determination of the structures and parameters
of different solid samples.
•The measured magnitude in a small angle scattering experiment
is the intensity as a function of the momentum transfer
Q=4π/λ sinΘ (scattering vector).
• SANS techniques:
-The pin-hole SANS covers the conventional range of 1 to 100nm.
This range is exptended by the focusing SANS with either
mirrors or lenses up to 1000nm.
-The double crystal (Bonse Hart) diffractometer reaches length
scales in the μm range.
Information which can be
obtained by SANS
• Sizes, spatial correlations and shapes of particles, aglomerates, pores
and fractals in crystalline and amorphous states, as well as in solutions
on a length scale ranging from 1 nm up to several hundred nanometers
• Phase transitions
• Degree of polydispersity
• Aggregation numbers
• Molecular weight
• Geometric peculiarities
Special methods
Contrast Variation Method
– Determination of object density
– Investigation of system homogeneity
Label Method
– Analysis of density distribution inside the
object under study
YUMO-Frank Laboratory of Neutron Physics, Joint Institute of Nuclear Physics,
Dubna, Russia
1 – two reflectors;
2 – zone of reactor with
moderator;
3 – chopper;
4 – first collimator;
5 – vacuum tube;
6 – second collimator;
7 – thermostate;
8 – samples table;
9 – Vn-standard;
10 – ring-wire detector;
11 – position-sensitive
detector "Volga";
12 – direct beam
detector.
SAXS and SANS comparison
Commons: - elastic
- coherent
- magnetic
scattering
- nuclear
Differences : SAXS
- big scattering angle
- q range = 0.8 ÷1 Å-1
SANS
- small scattering angle
- q range= 0.001 ÷1 Å-1
Conclusions to Part 2
• SANS is a powerful method for the investigation of sizes,
shapes and density of particles in the range of: 20 ÷ 10 000Å.
• The neutron measurements also enable the determination of
magnetic correlations inside samples.
• Contrast variation methods in the SANS framework allow
nuclear and magnetic density estimates.
• Etc.
References
• “Transport phenomena in La0.54Ho0.11Sr0.35Mn1-xCuxO3 manganites”
Mihail-Liviu Craus1,2, Nicoleta Cornei 3, Ahmed Islamov2 and Vasyl M.
Garamus4
• http://www.ill.eu/sites/fullprof/
• www.flnr.jinr.ru
• Neutron Scattering, Thomas Brϋckel, Gernot Heger, Dieter Richter
and Reiner Zorn, RWTH Aachen, University of Mϋnster
•
Perovskiti Magnetorezistivi: sinteza, proprietati si aplicatii, MihailLiviu Craus, Nicoleta Cornei, Mihai Lozovan, Viorel Dobrea,
Iassy:Alfa, 2008
•
An introduction to the program FullProf, Juan Rodríguez-Carvajal,
Laboratoire Léon Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif sur
Yvette Cedex, FRANCE
Acknowledgments
• We are indebted to the Project leaders for their guidance &
patience.
• Thanks to the Direction and staff of UC for the nice organization
of the summer student practice
• Thanks to Prof. Dr. Gh. ADAM and Dr. S. ADAM for advice during
the Summer practice
• Thanks to Dr. O. CULICOV for the Reactor tour
• Also thanks to Phd. Student R. ERHAN for good advices during the
Summer practice
Thank you for attention!!
Thank You for Attention!!