Basics of XRD part IV

Transcription

1 Basics of XRD part IV Dr. Peter G. Weidler Institute of Functional Interfaces IFG 1 10/31/17 KIT The Research University in the Helmholtz Association Name of Institute, Faculty, Department

2 Overview Instrumentation X-ray source Slits,... Detectors Measurement Data evaluation positions, phase identification lattice parameters quantitative XRD November 2017

3 crystallite and scattered x-ray: powder trace of detector circle November 2017

4 X-ray tube November 2017

5 selection of wavelength high absorption fluorescence --> Fe-bearing minerals (edge at 7.1keV (K β ) --> Cu K α at 8.0 kev --> λ = 1.24/keV --> nm November 2017

6 fluorescence Elements which fluoresce with Cu, Co or Cr radiation November 2017

7 increased background November 2017

8 Focusing elements: slits Soller slit Soller slit November 2017

9 slit setting and illuminated area Slits [mm ] Slits [ ] θ = θ = θ = θ = θ = θ = θ = θ = θ = θ = goniometer radius = 200. L = R * tan(α) / sin(θ) L irradiated sample length [cm] R diffractometer radius [cm] α angular opening of slit variable slit November 2017

10 Focusing elements: mirrors bend single crystal with defined face beam widening sample with irregular shape monochromatic beam removal of K β -part + line shape - intensity (70% loss) November 2017

11 Focusing elements: monochromator Quartz (101) 1 divergence slit 0.15 receiving slit with... after: November 2017

12 sample position detector X-ray tube horizontal 9-fold......and X fold... transmission capillary tube November 2017

13 detectors solid-state single channel counter time saving! scan θ, θ, 5 sec per step: SCC: LynxEye : 16 hrs 40' 0'' 5' 13'' 192-stripe counter November 2017

14 accessories heating stages for temperatures from below 0 C up to over 2000 C in-situ measurements in different atmospheres (air, N 2, He, CO 2 etc...)... and much more different set-ups, e.g. grazing incident, reflectometry... more examples and explanations: November 2017

15 Measurement What is important? Is XRD the right method for your problem?!?!?!? If YES --> sample material: e.g. stable at air, dry, moist etc.. amount available --> what do you want to know from the sample? --> composition or type of material (single phase) what is it? --> lattice parameters --> e.g. substitutions --> composition (mixture) how much of what? IF convincing answers --> THEN measurement parameters November 2017

16 Measurement parameters 4 important measurement parameters: start end step width counting time per step --> measurement time compromise between measurement time and number of samples = total time and availability of XRD machine... but do not forget: grabby data, grabby results November 2017

17 data evaluation Hematite Lin (Counts) Theta - Scale spheric hematite aggregate - File: hem_sphere.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 20. s - Temp.: 25 C (Room) - Time Started: 17 s - 2-Theta: Theta: Phi: November 2017

18 data evaluation - peak position Hematite d=2,69 hand-picking of peak positions, or... Lin (Counts) d=2, d=1, d=3,68 d=1, d=2, Theta - Scale spheric hematite aggregate - File: hem_sphere.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 20. s - Temp.: 25 C (Room) - Time Started: 17 s - 2-Theta: Theta: Phi: automatic peak picking November 2017

19 data evaluation - phase identification Angle d value Intensity Intensity % 2-Theta Å Count 24,202 3, ,6 33,202 2, ,0 35,685 2, ,8 39,316 2, ,6 40,921 2, ,7 43,585 2,07 54,0 1,9 49,517 1, ,0 54,082 1, ,0 57,588 1, ,4 62,452 1, ,1 64,035 1, ,0 68,391 1,37 23,0 0,8 69,576 1,35 64,0 2,3 71,918 1, ,4 72,150 1, ,2 74,833 1,27 22,0 0,8 75,486 1, ,3 77,762 1,23 59,0 2,1 77,953 1,22 48,0 1,7 78,818 1,21 32,0 1,1 79,976 1,20 29,0 1,0 80,727 1,19 86,0 3,1 identify peaks positions with positions of known materials November 2017

20 data evaluation - automatic search November 2017

21 data evaluation Hematite Lin (Counts) Theta - Scale spheric hematite aggregate - File: hem_sphere.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 20. s - Temp.: 25 C (Room) - Time Started: 17 s - 2-Theta: Theta: Phi: (C) - Hematite - Fe2O3 - Y: % - d x by: 1. - WL: Rhombo.H.axes - a b c alpha beta gamma Primitive - R-3c (167) I/Ic PDF November 2017

22 quantitative work 4000 top soil; dust particles 3000 Lin (Counts) Theta - Scale ED sample M2 - File: ED_M2.raw - Type: Locked Coupled - Start: End: Step: Step time: s - Temp.: 25 C - Time Started: 14 s - 2-Theta: Theta: Chi: Phi: X: November 2017

23 quantitative work - data bank 4000 top soil; dust particles 3000 Lin (Counts) ED sample M2 - File: ED_M2.raw - Type: Locked Coupled - Start: End: Step: Ste (C) - Quartz low - SiO2 - Y: % - d x by: 1. - WL: Hexagonal - a b (C) - Calcite - Ca(CO3) - Y: % - d x by: 1. - WL: Rhombo.H.axes - a b (C) - Kaolinite - Al2(Si2O5)(OH)4 - Y: % - d x by: 1. - WL: Triclinic - a b (C) - Muscovite 2M1 - K0.86Al1.94(Al0.965Si2.895O10)((OH)1.744F0.256) - Y: 9.39 % - d x by: (C) - Hematite, syn - Fe2O3 - Y: 3.13 % - d x by: 1. - WL: Rhombo.H.axes - a (C) - Sanidine - K0.42Na0.58Ca0.03AlSi3O8 - Y: 2.35 % - d x by: 1. - WL: Monoclinic (C) - Chabazite, syn - H3.1Ca0.25Al3.60Si8.40O24 - Y: 5.47 % - d x by: 1. - WL: Rhom 2-Theta - Scale (I) - Gibbsite, syn - Al(OH)3 - Y: 3.13 % - d x by: 1. - WL: Monoclinic - a b November 2017

24 quantitative work - additives addition of -- standard material -- same material mixtures: absorption coefficient of additive close to samples example: top soil / dust particles how much quartz is present? addition of known amounts of quartz to sample XRD at exactly the same conditions November 2017

25 quantitative work - additives intensity of phase a I a = K a X a / ρ a (μ/ρ) matrix with (μ/ρ) matrix mass absorption coefficient K a set-up constant X a rel. amount of phase a <--> CuKα 11% reduction in 10cm air!! addition of standard or same material I a / I std = (C a K a )/ (ρ a (μ/ρ) matrix )/( C std K std )/ (ρ std (μ/ρ) matrix ) I a / I std = (C a / C std ) K' with K' = (K a ρ std ) / (K std ρ a ) C a = (I a C std ) / ( I std K' ) = concentration of interesting material I a measured C std known I std measured K' calculated with standard November 2017

26 quantitative work - K' determination Lin (Counts) Theta - Scale November 2017

27 quantitative work addition of -- standard material -- same material satellite peaks!! avoid peak overlap <--> intensity determination check for particles orientation effects Lin (Counts) top soil; dust particles top soil; dust particles Lin (Counts) Theta - Scale 2-Theta - Scale November 2017

28 quantitative work more advanced and appropriate techniques: --> Lev S. Zevin & Giora Kimmel Quantitative X-ray Diffractometry Springer pp. more possibilities --> Rietveld Method November 2017

29 quantitative work Rietveld method: whole pattern approach what does it need: 1. space group 2. lattice parameter 3. fractional coordinates } structure file... good data November 2017

30 quantitative work Lin (Counts) Example: estimation from with peak height fit 4 oxides Result: XRD XRF Corundum Fluorite Zincite Brucite Zincite too high and underestimation of Brucite --> preferred orientation!! Theta - Scale File: CPD-2.RAW - Type: 2Th/Th locked - Start: End: Step: Step time: 3. s - Temp.: 25 C (Room) - Time Started: 0 s - 2-Theta: Theta: Aux1: Aux2: Aux3: Display p (*) - Corundum, syn - Al2O3 - Y: 8.92 % - d x by: 1. - WL: Rhombo.H.axes - a b c alpha beta gamma Primitive - R-3c (167) I/Ic P (C) - Fluorite - CaF2 - Y: % - d x by: 1. - WL: Cubic - a b c alpha beta gamma Face-centered - Fm-3m (225) I/Ic PDF S-Q (*) - Zincite, syn - ZnO - Y: % - d x by: 1. - WL: Hexagonal - a b c alpha beta gamma Primitive - P63mc (186) I/Ic PDF 1. - S (I) - Brucite, syn - Mg(OH)2 - Y: % - d x by: 1. - WL: Hexagonal - a b c alpha beta gamma Primitive - P-3m1 (164) I/Ic PDF November 2017

31 quantitative work Rietveld approach: with PO for Brucite GOF 1.35 R exp 8.56 R wp Result: XRF XRD Δ Corundum Fluorite Zincite Brucite November 2017

32 but getting to Rietveld, it needs the basics for Rietveld... next lecture November 2017

33 Literature F. Donald Bloss Crystallography and Crystal Chemistry Mineralogical Society of America, 1994, pp BRL D.L. Bish & J.E. Post (Eds) Modern Powder Diffraction Reviews in Mineralogy Vol 20 Mineralogical Society of America, 1989, pp BRL H.P. Klug & L.E. Alexander X-ray Diffraction Procedures Wiley, 1954, pp.716 (second hand bookstores BRL) B.E. Warren X-ray Diffraction Dover Publications, 1969, 1990, pp BRL D.M. Moore &R.C. Reynolds X-ray Diffraction and the Identification and Analysis of Clay Minerals Oxford University Press, 1997, pp BRL November 2017

34 Acknowledgment Bruker AXS Germany, Knielingen CEFET UMFG INCT-Acqua November 2017