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Neutron Diffraction Patterns Measured with a High-Resolution Powder Diffractometer Installed on a Low-Flux Reactor

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Neutron Diffraction Patterns Measured with a High-Resolution Powder Diffractometer Installed on a Low-Flux Reactor Neutron diffraction patterns measured with a high-resolution powder diffractometer installed on a low-flux reactor V. L. Mazzocchi1, C. B. R. Parente1, J. Mestnik-Filho1 and Y. P. Mascarenhas2 1 Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP), CP 11049, 05422-970, São Paulo, SP, Brazil 2 Instituto de Física de São Carlos (IFSCAR-USP), CP 369, 13560-940, São Carlos, SP, Brazil E-mail of corresponding author: [email protected] International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco Research Reactor Center (CRPq) CRPq’s main program - Nuclear and condensed matter physics - Neutron activation analysis - Nuclear metrology - Applied nuclear physics - Graduate and postgraduate teaching - Reactor operators training IEA-R1 Reactor - Swimming pool type, light water moderated with 23 graphite and 9 beryllium reflectors, designed to operate at 5 MW - Current power: 4.5 MW - Neutron in core flux: 7,0 x 1013n/cm2.s - Suitable for the use in: basic and applied research, production of medical radioisotopes, industry and natural sciences applications. International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 1- Characteristics of the old and the new neutron diffractometers The old IPEN-CNEN/SP neutron multipurpose diffractometer . a single BF3 detector . a single wavelength ( =1.137 Å) . a point-to-point scanning data measurement The new IPEN-CNEN/SP neutron powder diffractometer . a Position Sensitive Detector (PSD) array formed by 11 linear proportional 3He detectors, scanning a 2 = 20° interval . 400 intensity points measured in a single 2 step all at once (2 = 0.05°) . 4 different s: 1.111, 1.399, 1.667, 2.191 Å International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 2- Aurora – High Resolution Powder Diffractometer* Neutron monochromator Rotating-Oscillating Sapphire filter (inside the main shield) Collimator (ROC) (inserted into the in-pile collimator) Position Sensitive Detector (PSD) (inside the PSD shield) Beam shutter (inside the main shield) Main neutron shield PSD neutron shield Movable platform Extra shield 2- drive mechanism *Parente, C. B. R., Mazzocchi, V. L., Mestnik-Filho, J., Mascarenhas, Y. P., Berliner, R. Nucl. Instr. and Meth. in Phys. Res. A 622 (2010) 678-684. International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 3- Electronics associated to the HRPD “Aurora” Control and data acquisition PC Beam shutter control PEMs ROC control Pulser + neutron 2/ω angle indicators monitor electronics 2 stepper motor Ambient BG driver electronics Monochromator PC monitor and control modules keyboard (rocking, tilting and translation) PSD HV source Two-pen recorder (neutron monitor + ambient BG) (HRPD = High Resolution Powder Diffractometer) International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 4- Aurora – High Resolution Powder Diffractometer* PSD + focusing Si bent monochromator in comparison to the . powder patterns with higher resolution old diffractometer . rate of data collection higher by an average factor of 600 (per intensity point) . more s available, more different materials can be studied Great interest of the scientific and technological communities for crystallographic studies in new materials. International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 5- Resolution curves for the HRPD “Aurora” 1.3 Al O 2 3 1.2 1.1 Sample holder 0.125" dia. Sample holder 0.250" dia. 1.0 Sample holder 0.375" dia. 0.9 0.8 0.7 FWHM 0.6 0.5 0.4 0.3 0.2 20 40 60 80 100 120 2 (degree) International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 6- The Rietveld Method Fitting of an experimental powder diffraction pattern by the profile of a theoretical pattern, calculated according to a structure model assumed for the material under analysis. Deviation between experimental and theoretical patterns is minimized by the least-squares method. Analysis of multiphase patterns obtained with x-rays or neutrons: - refinement of the structural parameters of the phases; - quantitative phase analysis; - microstructural phase analysis (surface roughness effects, microabsorption and mean grain size). Definition of the numerical criteria of fit Σ yi(obs) yi(calc) RP = R-pattern: R 100 p Σy (obs) i 2 wi[yi(obs) yi(calc)] 1 RWP = R-weighted pattern: R 100 , with wi = wp 2 yi (obs) wiyi (obs) (NP) Re = R-expected: Re 100 2 wiyi (obs) R wp Goodness-of-fit: S = or 2 = S2 Re International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 7- Rietveld profile fit for Fe2O3 Crystalline structure: Space Group R 3 c (trigonal) 3 nuclear indexing Atomic positions Fe (4c) and O (6e) magnetic indexing 2 neutrons) 4 1 Intensity (10 Intensity 0 Fe 20 40 60 80 100 120 O 2 (degree) Magnetic structure: Time of measurement = 48 h Numerical criteria of fit: - RP = 0.047 Reactor power = 4.0 MW Antiferromagnetic - (Fe) = 4.9 - RWP = 0.060 B - Reduced 2 = 3.4 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 8- Rietveld profile fit for NiO Crystalline structure: 50 Space Group Fm3m (cubic) Atomic positions Ni (4a) and O (4b) 40 Nuclear + magnetic indexing 30 neutrons) 3 20 Intensity (10 Intensity Ni 10 O Magnetic structure: 0 2+ Antiferromagnetic - (Ni ) = 2 B 10 20 30 40 50 60 70 80 90 100 110 120 130 2 (degrees) Time of measurement = 48 h Numerical criteria of fit: - RP = 0.041 Reactor power = 4.0 MW - RWP = 0.051 - Reduced 2 = 2.9 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 9- Rietveld profile fit for BaY2F8:Nd Work in cooperation with ‘Laboratório de Crescimento de Cristais do IPEN-CNEN/SP’ Crystalline structure: 2 Space Group C2/m (monoclinic) Atomic positions Ba (2a); Y,Nd(4h) and F(8j) neutrons) 3 Numerical criteria of fit: - RP = 0.040 1 - RWP = 0.051 Intensity (10 Intensity - Reduced 2 = 1.2 Time of measurement = 24 h 0 Reactor power = 2.0 MW 20 40 60 80 100 120 2 (degree) * f for (sen)/ = 0.5 Å-1 Neutrons X Rays Element Z b b2 f * f2 (cm-1) (10-12 cm) (10-24 cm2) (cm-1) (10-12 cm) (10-24 cm2) F 9 ----- 0.565 0.3192 ----- 0.75 0.5625 Y 39 0.031 0.775 0.6006 596 5.4 29.16 Ba 56 0.01 0.507 0.2570 1155 8.3 68.89 Nd 60 0.76 0.769 0.5914 2580 9.0 81.0 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 10- Rietveld profile fit for Pb0.6Ba0.4Zr0.65Ti0.35O3 (PBZT40) Work in cooperation with ‘Laboratório de Cristalografia do IFUSP- São Carlos’ 5 Crystalline structure: Space Group Pm3m (cubic) 4 Atomic positions Pb,Ba (2a); Zr,Ti(4h) and O(8j) 3 neutrons) 3 2 Intensity (10 Intensity 1 Pb, Ba Zr, Ti O 0 10 20 30 40 50 60 70 80 90 100 110 120 130 2 (degree) Numerical criteria of fit: - RP = 0.048 Time of measurement = 30 h - RWP = 0.063 Reactor power = 2.0 MW - Reduced 2 = 1.4 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 11- Rietveld profile fit for ReO2 Work in cooperation with ‘Departamento de Física Aplicada da UFES’ Crystalline structure: Space Group P21/c (monoclinic) Atomic positions Re (4e); O(4e) 10 photons) 3 5 Intensity (10 Intensity 0 Re O 20 40 60 80 100 120 2 (degrees) Numerical criteria of fit: - R = 0.019 Time of measurement = 54 h P Reactor power = 3.5 MW - RWP = 0.025 - Reduced 2 = 2.7 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 12- Rietveld profile fit for Ta2O5 Work in cooperation with ‘Laboratório de Crescimento de Cristais do IFUSP - São Carlos’ 6 Crystalline structure: 5 Space Group Pmm2 (orthorrombic) 4 Ta O 3 neutrons) 3 2 Intensity (10 Intensity 1 0 Numerical criteria of fit: - RP = 0.021 - RWP = 0.027 - Reduced 2 = 1.9 20 40 60 80 100 120 2 (degrees) Time of measurement = 57 h * f for (sen)/ = 0.5 Å-1 Reactor power = 3.5 MW Neutrons X Rays Element Z b b2 f * f2 (cm-1) (10-12 cm) (10-24 cm2) (cm-1) (10-12 cm) (10-24 cm2) O 8 ----- 0.580 0.3364 ----- 0.62 0.3844 Ta 73 0.7 0.692 0.4789 2750 11.3 127.69 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 13- Rietveld profile fit for Be3Al2Si6O18 Work in cooperation with ‘Instituto de Física da USP – São Paulo’ Be3Al1.89Fe0.11Na0.25Si6O18 (beryl) Be3Al1.83Fe0.17Na0.03Si6O18 (aquamarine) 20 20 Be Al Si O Be Al Si O 3 2 6 18 3 2 6 18 SiO SiO 2 2 15 15 Al O Al O 2 3 2 3 neutrons) neutrons) 3 10 3 10 Intensity (10 Intensity Intensity (10 Intensity 5 5 2 Aquamarine: RP= 2.4%; RWP= 3.4%; reduced = 4.7; S= 2.2 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 10 20 30 40 50 60 70 80 90 100 110 120 130 2 (degrees) 2 (degrees) Time of measurement = 54 h Reactor power = 3.5 MW Wt. % (Be3Al1.89Fe0.11Na0.25Si6O18) = 96.94 Be Wt. % (Be3Al1.83Fe0.17Na0.03Si6O18) = 97.87 Wt. % (SiO2) = 2.70 Al Wt. % (SiO2) = 1.75 Wt. % (Al2O3) = 0.36 Si Wt. % (Al2O3) = 0.38 O Numerical criteria of fit: - RP = 0.022 Numerical criteria of fit: - RP = 0.024 - RWP = 0.032 - RWP = 0.034 - Reduced 2 = 4.0 - Reduced 2 = 4.7 International Conference on Research Reactors 14-18 November 2011 Rabat, Morocco 14- Neutron diffractometry at IPEN-CNEN/SP At present: -Rietveld quantitative phase analysis of powder patterns measured at room temperature In the near future: - Measurements at high and low temperatures - Measurements at high pressure (room temperature) - Residual stress measurements Scientific staff: - Dr.
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