In-situ X-ray Diffraction Instruments & Applications

Transcription

1 In-situ X-ray Diffraction Instruments & Applications Christian Resch Anton Paar GmbH, Graz Contents 1. Short Intro to X-ray Techniques and Laboratory Instrumentation for Structure Analysis Wikipedia 2. Sample Stages for In-situ X-ray Diffraction under Non-ambient Sample Conditions 3. Application Examples 4. Small Angle X-Ray Scattering Intensity [a.u.] q [1/nm] 2 1

2 X-ray Techniques for Structure Analysis Single Crystal (SCD) X-ray diffraction (XRD) Powder diffraction (PXRD) 2D-Diffraction Tomography (3D) Pole figures Reflectivity Grazing incidence Small Angle X-ray Scattering (SAXS) Nano-particles in solution Grazing incidence SAXS (GI-SAXS) 3 Powder and 2D XRD Powder XRD Standard analytical tool at universities and in the industry Simple diffractometers with only two mechanical circles to rotate either source and detector (θ-θ) or sample and detector (θ-2θ) Measurements are quick and data evaluation straight forward Many materials are produced/used as powders or polycrystalline material: pharmaceuticals, ceramics, metals, building materials (cement, ), catalysts, polymers, 2D XRD Mainly for materials preferred orientation of crystals and layered structures o Texture o Internal stress o Layer propertries: thickness, interface roughness, stress, particle orientation, Diffractometers and measurements more complicated: o 2D detectors o More mechanical circles (up to 5) 4 2

3 Typical Laboratory Diffractometers PANalytical Empyrean Bruker D8 Discover Bruker D2 Phaser Benchtop diffractometer no special supplies required very limited variability Rigaku Smartlab Other Suppliers: STOE&Cie GE Inspection Technologies Inel. 5 Why in-situ analysis? PhaseEquilibria Reaction Kinetics Crystal Structure Analysis Fundamental Description of the Material System Oxidation, Reduction, Corrosion Anisotropic Thermal Expansion Crystallization from Glasses /Liquids Optimize Thermal Processing for Improved Material Performance Solid Solution Composition Source: S. Misture; Materials Science & Engineering, Alfred University, NY, USA Denver X-ray Conference 2008 Phase Transformations Quantitative Analysis Polycrystalline Texture Crystallite Growth & Microstrain 6 3

4 Non-ambient Sample Stages - Oberview Commercially available non-ambient sample stages for laboratory X-ray instruments: Heating and cooling 260 to C Relative humidity (climate chambers) 5 95 %rf up to 60 C Variable gas pressure < mbar to 100 bar Reactive and explosive gases Mechanical tension and compression Pressure cells up to several GPa Flow cells to study reactions, crystal growth and agglomeration Battery cells for electrical load 7 Temperature Stages for PXRD Furnace Strip Heater Direct Heating+Cooling Gas Flow Cooler+Heater Oxford Cryosystems 1 temperature controlled housing 2... X-ray window 3 heating/cooling device 4 sample carrier 8 4

5 Sample Stages for 2D-diffraction Temperature stage 2 Tensile stage Diamond Anvil Cell (High pressure) 3 1 Load cells 1. Air-cooled housing 2. Heater = sample carrier 3. X-ray window (dome) ~ 100 GPa Source: Pamela C. Burnley, University of Nevada, Las Vegas 9 Comparison of Temperature Stages Furnace heater + Good temperature homogeneity + most reliable sample temperature measurement + Easy sample exchange + sample sample holder reactions unlikely + Sample spinning possible heating only max K slower heating/cooling than direct heaters temperature control not so good at T < 650 K sample holder expansion residual oxygen Direct heater/cooler + Very high/low temperatures possible + Very fast heating/cooling + Temperature control less dependent on the atmosphere inside the sample stage + Simpler instrument design, cheaper instrument sample preparation difficult (strip heater) sample temperature uniformity not so good sample temperature deviation sample sample holder reactions (strip heater) Gas flow heater/cooler + only option for single crystals and cooling of capillaries + transmission geometry + small background from sample holder (glass) + sample spinning + no sample displacement limited to low and medium high temperatures sample temperature uniformity difficult (capillaries) accurate temperature measurement difficult 10 5

6 Synthesis of Semiconducting Nanoparticles & Particle Growth ZnS and ZnO belong to the group of II-VI semiconductors. Materials for many possible applications (solar cells, infrared windows, lasers, displays, ). Optical and optoelectronic properties of nanoparticles are size-dependent control of the crystallite size required. Various synthesis methods established, but low-cost, time-saving synthesis methods are still under investigation. Established synthesis method [1] for ZnS from cheap precursors, followed by an oxidation in air to ZnO. [1] Lu, H.-Y.; Chu, S.-Y.; Tan, S.-S. Journal of Crystal Growth (2004), 269, Semiconducting Nanoparticles Experimental Formation of ZnS nanoparticles In N 2 at 1 bar rel. Studied Parameters: Sample heating stage for Reactive gases Temperature up to 900 C Oxidation to ZnO nanoparticles Gas pressure up to 10 bar ZnS samples oxidized in air at 600 C. Heating ramp: 100 C/min Sample of ZnS (100 C; 50 C/min) used to evaluate the conversion time Study done by A. Pein Anton Paar GmbH For other ZnO samples: Time for conversion 15 min 12 6

7 Semiconducting Nanoparticles Formation of ZnS Scherrer Equation d particle size K form factor (2θ) peak FWHM θ peak angle Final ZnS particles broader peaks smaller nanoparticles Crystallite sizes depending on formation conditions 13 Semiconducting Nanoparticles Formation of ZnO Oxidation of ZnS to ZnO nanoparticles Resulting ZnO nanoparticles (Scans stacked) 14 7

8 Semiconducting Nanoparticles Results Formation of ZnS Formation of Cubic ZnS (Sphalerite) Size range: nm (Scherrer equation) Influence of temperature: o bigger crystallite size at higher T Influence of reaction time: o bigger particles at prolonged reaction time Influence of heating ramp: o no clear trend concerning the size o relative and absolute growth rate increased at lower ramp speed Formation of ZnO Formation of Hexagonal ZnO (Wurtzite) Size range: nm Conversion time: o after 10 minutes at 600 C no ZnS reflections left o formation of ZnO has nearly finished ZnS particles synthesized at 100 C and 300 C give similar sized ZnO nanocrystallites (20.5 to 23.7 nm) ZnS particles from 200 C give significantly smaller ZnO crystallites (around 13 nm) 15 Hydrogen Storage Materials Hydrogen as energy carrier The ideal solid state H 2 storage material light high H 2 content reversible absorption and desorption T<180 C, p<50 bar rapid kinetics Hydrogen storage Gas tanks bar Liquid H 2 tanks -253 C Solid state matrix Source: M.Sommariva, PANalytical B.V. Almelo, NL Source: Sandia Nat. Labs 16 8

9 H 2 Storage in LaNi 5 LaNi 5 +H 2 as a model system for H 2 storage H 2 Storage capability of LaNi 5 long known Properties of LaNi 5 : o Stable in air o Adsorption/desorption reversible and under moderate conditions o Storage capacity low (1 wt% of H 2 ) Adsoprtion/Desorption mechanism LaNi 5 + 3H 2 LaNi 5 H 6 1 st adsorption and desorption slow Subsequent adsorption and desorption fast 17 H 2 Storage in LaNi 5 - Experimental 1st 100 C and 65 bar H 2 50 C in vacuum 50 C and 5 bars H 2 50 C in vacuum HPC 900 High-Pressure chamber on X Pert Pro diffractometer 18 9

10 H2 Storage in LaNi 5 - Result Data collection quick scans over characteristic peaks for good time resolution 1 st desorption Cycles of adsorption and desorption Data analysis peak area of characteristic peaks M. Sommariva PANalytical B.V. Almelo, NL C. Resch Anton Paar GmbH 19 Small Angle X-ray Scattering A long scientific tradition in Graz 1957 Kratky Small-Angle X-ray Scattering Camera Prof. Otto Kratky, Univ. of Graz first SAXS instrument worldwide first scientific instrument produced by Anton Paar GmbH > 600 systems sold worldwide 2003 SAXSess system jointly developped by Prof. Otto Glatter, successor of Prof. Kratky, and Anton Paar GmbH with X-ray mirror, wide-angle capability, point collimation, Since 2005 sold directly by Anton Paar as a complete X-ray instrument 2012 New SAXSpace system developped by Anton Paar GmbH with large sample chamber, auto-alignment, new instrument control software, 20 10

11 Small Angle X-ray Scattering (SAXS) (1) SAXS informs about: a) Particle Shape and Size OR Particle-Size Distribution b) Surface-To-Volume Ratio c) Molecular weight OR Particle Density Size / size distribution Shape Internal Structure Porosity Degree of Crystallinity Moleculare Weight (2) SAXS investigates structures indirectly (3) SAXS delivers averaged numbers 21 The Purpose of SAXS A method to investigate o Morphologies o Structures o Particle Architectures Microscopy Optical lens Visible image Scattering Reconstruction just as microscopy does BUT. Object Detector Light Source SAXS Fourier transformation Picture Mathematical reconstruction 22 11

12 Microscopy and Scattering Microscopy Scattering Small Details & Local Structure Easily detected. Are lost. Average values Hard to obtain. Are always obtained. Preparation artefacts Results are: Hard to prevent. Unique but with bad statistics. Are rare. Ambiguous but with good statistics. (1) The methods are complementary. (2) You need both methods to get the complete picture! 23 SAXS Ingredients Small-Angle (SAXS): deg Wide-Angle (WAXS, XRD): deg Scattering Angle 2 X-Ray Source Collimation System Sample Beam Stop Detector + Software 24 12

13 Investigating Nano-particles: SAXS Measurement gives scattering pattern Scattered intensity is recorded by a detector and is processed mathematically Scattering Object Reconstruction Detector Software Light Source There are no x-ray lenses in SAXS instruments 25 SAXSess Simultaneous small- and wide angle scattering Crystalline particles, strong interaction WAXS: crystalline peaks Large d-spacing SAXS peaks SAXS WAXS 26 13

14 SAXSess Simultaneous small- and wide angle scattering Crystalline particles, strong interaction WAXS: crystalline peaks Small d-spacing WAXS peaks SAXS WAXS 27 Collimation Systems Point Collimation: Line Collimation: X-Ray Source X-Ray Source 28 14

15 Microfibril angle (MFA) in Natural Fibres The microfibril angle (MFA) of the cellulose fibers is directly proportional to the magnitude of the applied strain 1). 45 Coir fibre mounted on tensile stage X-rays 2D diffraction pattern of coir fibre while straining the sample. 38 Azimuthal integration along the 200 reflections. The position of the maximum is shifted to the center for the strained fiber. 29 1) K. J. Martinschitz, P. Boesecke, C. J. Garvey, W. Gindl, J. Keckes; J. Mater. Sci. 43 (2008) 350. Samples provided by Dr. Jozef Keckes, University of Leoben, Austria Change of MFA upon cyclic straining Non-ambient XRD Summary In-situ X-ray diffraction and scattering provides unique information about important material properties under controllable non-ambient conditions changes in crystal structure / crystal phase transformations transitions from amorphous to crystalline state and vice versa lattice parameters and expansion/contraction of the crystal structure recrystallization and crystallite growth chemical reactions internal stress layer and layer interface properties of layered structures nano-particle size and shape structural properties of nano-porous materials agglomeration and more averaged over a representative amount of material and with little sample preparation