QPA with Partial or No Known Crystal Structures (PONKCS) Innovation with Integrity

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1 QPA with Partial or No Known Crystal Structures (PONKCS) Innovation with Integrity

2 Classic Rietveld method IF All phases in the mixture are known All phases are crystalline All crystal structures are known THEN ZMV algorithm (1) can be used to relate the Rietveld scale factor to the phase concentration (1) Hill R.J. and Howard C.J. (1987) J. Appl. Crys. Vol 20, /12/2011 Advanced XRD Workshop 2

3 Classic Rietveld method ZMV calibration constant W α = n S k = 1 α S ( Z MV ) k α ( Z MV ) k W = weight % S = Rietveld scale factor Z = No. of formula units in unit cell M = molecular mass of formula unit V = unit cell volume ZMV is a calibration constant which eliminates the need to measure: instrument calibration constant sample mass absorption If the crystal structure of a phase is not known, then the ZMV calibration constant is unknown 14-15/12/2011 Advanced XRD Workshop 3

4 Classic Rietveld method internal standard The sample is "spiked" with a known mass of standard material and the QPA normalized accordingly The weight fractions of the crystalline phases present in each sample are estimated using the Rietveld methodology Concentrations to be corrected proportionately according to: Corr( W α ) = W STD STD known measured where Corr(W α ) is the corrected weight percent, STD known the weighted concentration of the standard in the sample and STD measured the analyzed concentration α The amount of amorphous material W amorphous can then be derived from: W = 1 If there is more than one phase with an unknown or only partially known structure, these phases will be considered as a single group = no info on individual phases! amorphous W j j= 1 n Corr( 14-15/12/2011 Advanced XRD Workshop 4 )

5 PONKCS method An individual unknown or partially unknown crystalline phase can be quantified through PONKCS method, if: the phase is available as pure specimen (or major phase in specimen known impurities that can be quantified with the internal standard method) a synthetic mixture can be prepared in which the amounts of unknown and an internal standard are known the unknown phase in the experimental mixture does not vary too much from the pure specimen, used to derive the intensities Phases with Partial Or No Known Crystal Structure are characterized by measured rather than calculated structure factors For all phases a using empirically derived structure factors ZMV "calibration constants" must be derived, e.g. via an internal standard s 14-15/12/2011 Advanced XRD Workshop 5

6 PONKCS method crystalline (and even amorphous) phases can be fitted through: (hkl) phase (Pawley or Le Bail) if the phase can be indexed peak phase if the phase cannot be indexed Result: list of peaks described by peak position and intensity This list of peaks replaces str in the Rietveld refinement, while keeping peak position and intensity fixed = group of peaks scaled as a single entity within Rietveld refinement ZMV constant is unknown and has to be provided through calibration 14-15/12/2011 Advanced XRD Workshop 6

7 PONKCS method Calibration through the preparation of a mixture containing known amounts of unknown (α) and standard material (s) W W α = s S S α s ( Z MV ) ( Z MV ) s α or W W ( ) α s Z MV = ( Z MV ) s α s S S α all known (ZMV) α has NO physical meaning 14-15/12/2011 Advanced XRD Workshop 7

8 PONKCS Applications in Industry "Nontronite Unknown structure Cement: QA of Bassanite Structure data of C3S do not accurately describe the technical product Cement: QA of blast furnace slag (BFS) Amorphous material (BFS) Cement: QA of C3S polymorphs (M1, M3) Structure data of C3S do not accurately describe the technical product 14-15/12/2011 Advanced XRD Workshop 8

9 Nontronite 14-15/12/2011 Advanced XRD Workshop 9

10 #1: Literature Diffraction pattern of nontronite (Co Kα)

11 #1: Refinement of standard mixture Sqrt(Counts) Th Degrees Corundum % Nontronite_hkl %

12 #1: Results The resultant phase model has been applied to a series of mixtures of known composition Nontronite Corundum 1.0 Bias (wt%) Weighed (wt%) 12

13 Cement 14-15/12/2011 Advanced XRD Workshop 13

14 PONKCS Example: Quantitative Analysis of Cement Nishi & Takeuchi (1985) C3S structure - misfits due to structural deficiencies Only a "cosmetic" issue for Clinker quantification Counts 8,000 7,500 7,000 6,500 6,000 5,500 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1, ,000-1,500-2,000-2,500-3, Th Degrees C3S monoclinic (NISHI) % C2S beta (MUMME) 8.02 % C3A Na orthorhombic 5.02 % C3A cubic 2.76 % C4AF Colville % Periclase 0.63 % Lime 1.24 % Arcanite K2SO % 14-15/12/2011 Advanced XRD Workshop

15 PONKCS Example: Quantitative Analysis of Cement Nishi & Takeuchi (1985) C3S structural deficiencies (intensity misfit) adversly affects Bassanite (CaSO 4 ½H 2 O) quantification due to unevitable peak overlap Degree of overlap depends on Alite chemical composition Counts 3,000 2,500 2,000 1,500 1, ,000 Alite (402) & (310) Bassanite C2S beta (MUMME) 0.00 % C3A cubic 0.00 % C3A Na orthorhombic 0.00 % C4AF Colville 0.00 % Lime 0.00 % Periclase 0.00 % Quartz 0.00 % Arcanite K2SO % Gypsum 0.00 % Bassanite Bezou 0.00 % Anhydrite 0.00 % Calcite 0.00 % Portlandite 0.00 % C3S monoclinic (NISHI) 0.00 % -1,500-2,000-2,500-3,000-3, Th Degrees /12/2011 Advanced XRD Workshop 15

16 PONKCS Structureless Modelling of Alite Substitution of calculated intensities phase_name C3S_hkl_Phase 0.1 MVW( 0, , 0) space_group 8 CS_L(cs_c3smonni, 1000 min =50; max =1000;) a a_c3smonni b b_c3smonni c c_c3smonni be be_c3smonni r_bragg hkl_is hkl_m_d_th I e- 010 hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I hkl_m_d_th hkl_m_d_th hkl_m_d_th I hkl_m_d_th I hkl_m_d_th I Counts Counts 1, , Classic Rietveld Refinement using the Nishi & Takeuchi (1985) C3S structure Th Degrees Th Degrees PONKCS refinement /12/2011 Advanced XRD Workshop 16

17 PONKCS Quantitative Analysis of Bassanite Classic Rietveld Refinement using the Nishi & Takeuchi (1985) C3S structure PONKCS refinement Bassanite: Estimated accuracy ~0.2% Estimated precision <0.1% 14-15/12/2011 Advanced XRD Workshop 17

18 Slag in Cement 14-15/12/2011 Advanced XRD Workshop 18

19 PONKCS Quantitative Analysis of BFSlag BFSlag can be described via Pawley / Le Bail or single peak fitting 14-15/12/2011 Advanced XRD Workshop 19

20 PONKCS Quantitative Analysis of BFSlag E.g. Pawley fit strategy: Chose arbitrary space group and lattice parameters to allow for a couple of peaks Allow for extreme line broadening Refined PONKCS model for BFSlag 14-15/12/2011 Advanced XRD Workshop 20

21 Round Robin VDZ 2006/7 Quantitative Analysis of BFSlag Preliminary results PONKCS: (5 repeated analyses) 25.1 (2) 67.2 (2) 71.7 (2) 14-15/12/2011 Advanced XRD Workshop 21

22 Round Robin VDZ 2006/7 Quantitative Analysis of BFSlag Accuracy and Precision (values in wt. %, SD in brackets/1σ) Every sample measured 5 times (D4 ENDEAVOR, LynxEye Detector) Reference values: sample 1: 25,0 wt.% sample 2: 67,0 wt.% sample 3: 72,0 wt.% BFSlag Sample 1 BFSlag Sample 2 BFSlag Sample 3 Measurement 1 25,0 67,2 71,7 Measurement 2 25,1 67,3 71,9 Measurement 3 24,7 67,0 71,6 Measurement 4 25,1 67,3 71,9 Measurement 5 25,3 67,0 71,5 Mean 25,1 67,2 71,7 SD 0,2 0,2 0, /12/2011 Advanced XRD Workshop 22

23 C3S Polymorphs 14-15/12/2011 Advanced XRD Workshop 23

24 PONCKS Alite Polymorphism The missing link for quality and process control In Cement Clinkers two monoclinic polymorphs of the main Phase Alite (C 3 S) can be found (M1 and M3) Both polymorphs are different in hydraulic properties, like strength development Although this is well know since decades, nobody was able to distinguish and quantify these polymorphs in the last years by XRD Rietveld analysis 14-15/12/2011 Advanced XRD Workshop 24

25 PONCKS Alite Polymorphism The monoclinic polymorphs M1 and M3 Very similar patterns Available structural data do not accurately describe the technical product Alite polymorph M1 Alite polymorph M3 Lin (Counts) Lin (Counts) M1 and M3 can be distinguished using currently available structure data! 14-15/12/2011 Advanced XRD Workshop 25

26 Alite Polymorphs Monitoring Compressive Strength Observation over months: continuous decrease of the early strength development, although all process control parameters remained unchanged The re-evaluation of the XRD data using TOPAS considering the Alite polymorphs showed a correlated decrease of the M1 polymorph 14-15/12/2011 Advanced XRD Workshop 26

27 Alite Polymorphs POLYSNAP + TOPAS QA Results PCA: 630 PXRD + M1/M3 alite HS clinker M1 high HS clinker M1 low normal clinker M1 high normal clinker M1 low 14-15/12/2011 Advanced XRD Workshop 27

28 PONCKS Alite Polymorphism The missing link for quality and process control By using the TOPAS PONKCS capabilities we are able to distinguish the Alite polymorphs M1 and M3 Provides more detailed information about the process Allows to understand and predict the early strength development Allows to control and improve the quality of the product 14-15/12/2011 Advanced XRD Workshop 28

29 PONKCS Reference Scarlett, N.V.Y. & Madsen, I.C. (2006) Quantification of phases with partial or no known crystal structure Powder Diffraction, 21(4), Note: The paper includes an example walk-through on a TOPAS keyword level 14-15/12/2011 Advanced XRD Workshop 29

30 Conclusions PONKCS allows the quantification of compounds, where the classic Rietveld method fails Materials with partial or no known crystal structure can be quantified with the same accuracy and precision as phases with crystal structure. Often even better, due to the calibration step Crystalline and amorphous phase amounts, accuracy and LLOD < 1% Preferred orientation can be dealt with (if sample is indexed) 14-15/12/2011 Advanced XRD Workshop 30

31 Copyright Bruker Corporation. All rights reserved. Innovation with Integrity