qpa withpartial ornoknowncrystal structures (ponkcs)secure site...

QPA with Partial or No Known Crystal Structures(PONKCS)

Innovation with Integrity

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, 467-474.

Classic Rietveld method

14-15/12/2011 Advanced XRD Workshop 2

• 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

( )( )∑

=

= n

kkk VMZS

VMZSW

1

ααα

W = weight %

S = Rietveld scale factor

Z = No. of formula units in unit cell

M = molecular mass of formula unit

V = unit cell volume

Classic Rietveld methodZMV calibration constant


• 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:

where Corr(Wα) is the corrected weight percent, STDknown the weighted concentration of the standard in the sample and STDmeasured the analyzed concentration

• The amount of amorphous material Wamorphous can then be derived from:

• 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!

Classic Rietveld methodinternal standard


measured

known

STD

STDWWCorr αα =)(

∑=

−=n

jjamorphous WCorrW

1

)(1

• 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

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 keepingpeak 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

PONKCS method


• Calibration through the preparation of a mixture containing knownamounts of unknown (α) and standard material (s)

• (ZMV)α has NO physical meaning

PONKCS method

( )( )sss VMZS

VMZS

W

W ααα =

or

( ) ( )ss

s

VMZS

S

W

WVMZ ⋅⋅=

α

αα

all known


Advanced XRD Workshop

• "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

PONKCS Applications in Industry

14-15/12/2011 8

Nontronite


10

#1: Literature

Diffraction pattern of nontronite (Co Kαααα)

1401351301251201151101051009590858075706560555045403530252015105

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

11

#1: Refinement of standard mixture

2Th Degrees9088868482807876747270686664626058565452504846444240383634323028262422201816141210864

Sqr

t(C

ount

s)

115

110

105

100

95

90

85

80

75

70

65

60

55

50

45

40

35

30

25

20

15

10

Corundum 49.78 %Nontronite_hkl 50.22 %

12

#1: Results

The resultant phase model has been applied to a series of mixtures of known composition

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60 70 80 90 100

Weighed (wt%)

Bia

s (w

t%)

Nontronite Corundum

Cement


• Nishi & Takeuchi (1985) C3S structure - misfits due to structuraldeficiencies

• Only a "cosmetic" issue for Clinker quantification

PONKCSExample: Quantitative Analysis of Cement

2Th Degrees656055504540353025201510

Cou

nts

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

500

0

-500

-1,000

-1,500

-2,000

-2,500

-3,000

C3S monoclinic (NISHI) 70.69 %C2S beta (MUMME) 8.02 %C3A Na orthorhombic 5.02 %C3A cubic 2.76 %C4AF Colville 10.20 %Periclase 0.63 %Lime 1.24 %Arcanite K2SO4 1.44 %


• Nishi & Takeuchi (1985) C3S structural deficiencies (intensity misfit) adversly affectsBassanite (CaSO4 · ½H2O) quantification due to unevitable peak overlap

• Degree of overlap depends on Alite chemical composition

PONKCSExample: Quantitative Analysis of Cement

2Th Degrees40383634323028262422201816141210

Cou

nts

3,000

2,500

2,000

1,500

1,000

500

0

-500

-1,000

-1,500

-2,000

-2,500

-3,000

-3,500

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 K2SO4 0.00 %Gypsum 0.00 %Bassanite Bezou 0.00 %Anhydrite 0.00 %Calcite 0.00 %Portlandite 0.00 %C3S monoclinic (NISHI) 0.00 %

Bassanite

Alite (402) & (310)


• Classic Rietveld Refinementusing the Nishi & Takeuchi (1985) C3S structure

• PONKCS refinement2Th Degrees

2019181716151413121110

Cou

nts

1,000

900

800

700

600

500

400

300

200

100

0

PONKCSStructureless Modelling of Alite

Substitution of calculated intensities

phase_name C3S_hkl_Phasescale @ 0.1MVW( 0, 4331.778506, 0)space_group 8CS_L(cs_c3smonni, 1000 min =50; max =1000;)a a_c3smonni 33.18748b b_c3smonni 7.05051c c_c3smonni 18.56319be be_c3smonni 94.22338r_bragg 0.006728277788

hkl_Ishkl_m_d_th2 0 0 2 2 9.25639439 9.54711437 I 2.05270142e-010hkl_m_d_th2 2 0 -2 2 8.34458351 10.5931587 I 0.01858485616hkl_m_d_th2 4 0 0 2 8.27434444 10.683341 I 0.01406196859hkl_m_d_th2 2 0 2 2 7.8363862 11.2822943 I 0.01484194695hkl_m_d_th2 4 0 -1 2 7.77032948 11.3785229 I 0.0251988569hkl_m_d_th2 4 0 1 2 7.35505056 12.0232773 I 0.03432590883hkl_m_d_th2 1 1 0 4 6.89578199 12.8272991 I 0.01149107085hkl_m_d_th2 1 -1 -1 4 6.49472332 13.6230459 I 0.04729996279hkl_m_d_th2 1 1 1 4 6.42985344 13.7611485 I 0.01753635023hkl_m_d_th2 4 0 -2 2 6.40786076 13.8086081 I 0.03122114305hkl_m_d_th2 0 0 3 2 6.17092943 14.3415194 I 0.003343324237hkl_m_d_th2 4 0 2 2 5.9548769 14.8647385 I @ 0.27078hkl_m_d_th2 3 1 0 4 5.94094992 14.8997831 I @ 1.2198hkl_m_d_th2 2 0 -3 2 5.92666531 14.9358988 I 0.007612890057hkl_m_d_th2 3 -1 -1 4 5.72322845 15.4700003 I 0.003767987738hkl_m_d_th2 2 0 3 2 5.64745855 15.6788511 I 0.01085298472…..

2Th Degrees2019181716151413121110

Cou

nts

1,000

900

800

700

600

500

400

300

200

100

0


PONKCSQuantitative Analysis of Bassanite

• Classic Rietveld Refinementusing the Nishi & Takeuchi (1985) C3S structure

• PONKCS refinement

• Bassanite:Estimated accuracy ~0.2%Estimated precision <0.1%


Slag in Cement


PONKCSQuantitative Analysis of BFSlag

BFSlag can be describedvia Pawley / Le Bail orsingle peak fitting


PONKCSQuantitative Analysis of BFSlag

14-15/12/2011 20Advanced XRD Workshop

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 PONKCSmodel for BFSlag

Round Robin VDZ 2006/7Quantitative Analysis of BFSlag

• Preliminary results PONKCS:

(5 repeated analyses)

25.1 (2)

67.2 (2)

71.7 (2)


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.%

Round Robin VDZ 2006/7Quantitative Analysis of BFSlag

BFSlagSample 1

BFSlagSample 2

BFSlagSample 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 0,2


C3S Polymorphs


The missing link for quality and process control

• In Cement Clinkers two monoclinic polymorphs of the main Phase Alite(C3S) 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

PONCKSAlite Polymorphism


The monoclinic polymorphs M1 and M3

• Very similar patterns

• Available structural data do not accurately describe the technical product

M1 and M3 can be distinguished using currently available structure data!


Alite polymorph M3

Lin

(Cou

nts)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

50 51 52 53 54

Alite polymorph M1

Lin

(Cou

nts)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

50 51 52 53 54


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 Alitepolymorphs showed a correlated decrease of the M1 polymorph


• PCA: 630 PXRD + M1/M3 alite

Alite PolymorphsPOLYSNAP + TOPAS QA Results

HS clinkerM1 high

HS clinkerM1 low

normal clinkerM1 high

normal clinkerM1 low


The missing link for quality and process control

• By using the TOPAS PONKCS capabilities we are able to distinguish the Alitepolymorphs 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



PONKCSReference

Scarlett, N.V.Y. & Madsen, I.C. (2006)

Quantification of phases with partial or no known crystal structure

Powder Diffraction, 21(4), 278-284

Note:

The paper includes an example walk-throughon a TOPAS keyword level


• 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)

Conclusions


qpa withpartial ornoknowncrystal structures (ponkcs)secure site...

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