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).
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)
Dr. M. L. CRAUS (FLNP)
Dr. A.I. KUKLIN (FLNP)Introduction to the difraction analysis and SANS method
JINR Summer Student Practice 5-25 July 2010
Part 1:Corelations between structure and transport caracteristics ofmanganites with Cr impurities(La0.54Ho0.11Sr0.35)(Mn1-xCrx)O3
Manganite samples with the general structure La0.54Ho0.11Sr0.35Mn1-xCrxO3 have been studiedusing 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.
La0.54Ho0.11Sr0.35Mn1-xCrxO3 manganites were prepared by sol-gel method using oxides and acetates and sintered in air at 1200C 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 reportwas obtained with Hubber-Guinier diffractometer by using Cr Kα1 radiation and was handled using FullProf Suite code.
The program has been mainly developed for Rietveld analysis (structure profile refinement) of neutron (nuclear and magnetic scattering) or X-ray 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/
• 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.
Work done within the Project
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).
-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.
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,
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.
Commons: - elastic
- magnetic scattering
Differences : SAXS - big scattering angle
- q range = 0.8 ÷1 Å-1
SANS - small scattering angle
- q range= 0.001 ÷1 Å-1
Thank you for attention!!