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Home , Aerinite, Birnessite, Glauconite, Kutnohorite, Sauconite, Vauxite

Issues in Quantitative Phase Analysis

Arnt Kern & Ian Madsen This document was presented at PPXRD - Pharmaceutical Powder X-ray Diffraction Symposium Sponsored by The International Centre for Diffraction Data

This presentation is provided by the International Centre for Diffraction Data in cooperation with the authors and presenters of the PPXRD symposia for the express purpose of educating the scientific community.

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PPXRD Website – www.icdd.com/ppxrd ICDD Website - www.icdd.com Issues in Quantitative Phase Analysis

Limitations in accuracy and precision are mostly experimental • Mathematical basis and methodology of quantitative phase analysis is well established and work OK • Errors arise during application of methods ("PICNIC")

Sample related errors • The material is not an "ideal powder" • Preferred orientation • Particle statistics • ... • Absorption • ... Issues in Quantitative Phase Analysis

Operator errors • Incomplete / wrong phase identification The Reynolds Cup – what is needed to win?

Mark D Raven and Peter G Self 29 July 2014

CSIRO LAND AND WATER / RESOURCES FLAGSHIPS Non clay minerals (2002-2012)

• (18) • Gypsum (2) • (1)

• K- (13) • Anhydrite (2) • (2) • Plagioclase (14) • Alunite (1) • Zircon (2) • (12) • Hematite (6) • (1) • (10) • (5) • Opal-CT (1) • Magnesite (4) • Magnetite (4) • Amphibole (3) • (3) • Anatase (9) • Zeolite (1) • Huntite (1) • Rutile (3) • Epidote (1) • Halite (6) • Ilmenite (3) • (1) • Pyrite (7) • Gibbsite (3) • Arcanite (1) • Siderite (8) • Bohmite (1) • Amorphous (6) • Barite (5) • (2)

63rd Denver X-ray Conference 28 July – 1 August 2014, Big Sky Resort, Montana, USA | Quantitative 5 | Phase Analysis Workshop Clay minerals (2002-2012)

• 2:1 Dioctahedral Clays (18) • Kaolin (15) • Smectite (, • (well and poorly ordered) ) • • Mixed layered (-smectite, • -smectite)

• /Illite ( 2M , illite 1 • Chlorite (11) 1Md, 1M) • Clinochlore, Ripidolite • 2:1 Trioctahedral Clays (6) • Serpentine (2) • Smectite () • Lizardite • • (3) • Mixed layered (corrensite) • (1) • Mica () • (1)

63rd Denver X-ray Conference 28 July – 1 August 2014, Big Sky Resort, Montana, USA | Quantitative 6 | Phase Analysis Workshop Misidentified phases (2002-2012)

• Actinolite • • Ilmenite • (2M1 ) • Vermiculite • Aegerine • Clinochlore • iIterstratified (tri) • Phlogopite (mica-trioctahedral) • Vermiculite Trioctahedral • Aerinite • Clinoenstate • • hydrate • Vermiculite/illite • Akaganeite • Clinoptilolite • Iron Iron • Plagioclase • Vermiculite-Smectite Trioctahedral • Albite/anorthite • ClinoPyroxene • Jarosite • Portlandite • Vesuvianite • • Clinozoisite • KAlSiO4 • Potarite • Wagnerite • Alluaudite Al -Mg• Cordierite • Kaolinite • • • Almandine • Corrensite • kaolinite/smectite • Pseudobrookite • • Al-Mg • Corundum • Kaolinite-Chlorite • Pumpellyite • Whitmoreite • AlO • Cotunnite • K-feldspar • Pyrite • Wollastonite • Alumina gamma • Cristobalite • Kieserite • • Wroewolfeite • Aluminite AlO • Cryptohalite • K-rich Chlorite • 1T • Wuestite • Alunite • Crysotile • • pyrophyllite 2M • Zeolite • Alunogen • Diaspore • Laueite • Pyroxene • Zeophyllite • Amorphous • Dickite • Laumonite • Pyroxene (Augite) • Zinnwaldite • Amorphous (Allophane) • Dickite/ • Lepidocrocite • Pyroxene (Ferroan Diopside) • Zircon • Amorphous KAlSi3O8 • Diopside • Leucite • Pyrrhotite • Zirconium sulphate hydroxide • Amorphous Si • Dolomite • Lime • Rectorite hydrate • Amorphous SiO2 • Dolomite/ • Lithosite • Reyerite • Zoisite • Amorphous Volcanic Glass • Elpidite • Lizardite • • Amphibole • Enstatite • Magnesioferrite • • Analcime • Epidote • Magnesite • Rodolicoite • Anatase • Euclase • Magnetite • Rutile • Andesine • Faujasite • Malachite • Sanidine • Anhydrite • Fe oxide • • Saponite • Ankerite • Fedorite • Melantenite • • Anorthite • Feldspar (Kspar) • Mg7Zn3 • Schorl • • Ferrihydrite • Mg-calcite Mg7Zn3• Sepiolite • Antlerite • Ferrite magnesian • MgSO4 • Serpentine • Apatite As2O3• • Mica • Siderite • Aragonite • Forsterite • Mica Trioctahedral • Siderite (Mn-rich) • Arcanite • Galeite • Mica-Vermiculite Trioctahedral • Siderite(not Mg) • Arsenolite As2O3 • Garnet • Microcline • Silicon • Augite • Gehlenite • Missing • Silicon dioxide Silicon • Barite • Gibbsite • • Sillimanite • Bazalt • Gismondine • Monohydrocalcite • Smectite trioctahedral • Berthierine • Glass/Obsidian • Montmorillonite (Tri) • • Biotite • Glauberite • Moschellandsbergite • Sodalite • Birnessite • Glauconite • Mullite • Spencerite • Bromcarnallite • Goethite • Nacrite • Sphalerite iron • Brookite • Gypsum • Na-Feldspar • Spinel • Brucite • Halite • Natrolite • Staurolite • Brushite C6H5O3PZn • Halite potassian • Nepheline Nitride• Strontianite • Bytownite • Halloysite • Nitride Silicon • Sylvite 260! • C6H5O3PZn • Hectonite • Nordstrandite • • Calcite • Hedenbergite • Norrishite Silicon• Szomolnokite • CaMg2Al16O27 • Hematite • Oligoclase • Talc • -fluorapatite • Hercynite • Olivine • Thenardite • Carnallite • Heulandite • Opal • Thermonatrite • CaSiO3 • Hexahydrite • Opal CT • Titanite • Celestine • Hornblende • Orthoclase • Titanomagnetite • Chabazite • Hotsonite • OrthoPyroxene • Tobermorite • Chalcosite • Hyalophane • Osumilite • Tourmaline • Chlorargyrite • hydrated Ca-Mg carbonate • Others not precisely identified • Trimerite • Chlorite Dioctahedral • Hydrocalumite • oxide 1 • Trydymite • Chlorite Trioctahedral • Hydrotalcite • oxide 2 • Tungstite • Chlorite-Montmorillonite(Tri) • Hydroxyapophyllite • Palygorskite • Unidentified • Chlorite-Smectite TrioctahedralChromite • Hydroxylapatite • Periclase • Unnamed hydrate • Chlorite-vermiculite • Hypersthene • Perovskite • Vaterite • Chromite • Illite Tri • Phillipsite •

63rd Denver X-ray Conference 28 July – 1 August 2014, Big Sky Resort, Montana, USA | Quantitative 7 | Phase Analysis Workshop Issues in Quantitative Phase Analysis

Operator errors • Incomplete / wrong phase identification • Incorrect crystal structures: , atom coordinates, occupancy factors, temperature factors • Use of poor profile / background models • Failure to refine parameters: Unit cell, profile parameters, ... • Refinement of parameters which are not supported by the data: Background, atom coordinates, occupancy factors, temperature factors, microstructure, ... Issues in Quantitative Phase Analysis

Operator errors, ctd. • Inappropriate use of correction models – just because you CAN doesn’t mean you SHOULD! • Preferred orientation correction • Absorption correction • Non-constant diffraction volume • ... • Acceptance of physically unrealistic parameters (esp. thermal parameters) • Acceptance of incomplete refinements • High values of R-factors • Refined parameters not checked • Visual fit of model not checked

IUCr CPD Round Robin on 0 Quantitative Phase Analysis 100 10 c • Experimental design for Sample 1 90 20 o Eight mixtures of 3 phases 80

– Corundum – -Al2O3 30 70 Z in c ite (w t% ) – Fluorite – CaF2 40 – Zincite – ZnO 60 o Each phase present at a 50 f 50 range of concentrations 60 o ~ 1.5, 5, 15, 30, 55, 95 wt% 40 Corundum (wt%) Corundum g 70 • ‘Simple’ system 30 o Well defined phases d 80 h o Minimal peak overlap e 20 90 o Little absorption contrast 10 b 100 a0 0 10 20 30 40 50 60 70 80 90 100 Fluorite (wt%)

10 | IanIan Madsen Madsen | | CSIRO TOPAS Training Resources Course– Level 1– Flagship 2013Level 1| || Quantitative2013 | Phase Analysis | DXC2014, Big Sky, Montana IUCr CPD Round Robin on QPA 0 1a 100 CPD Supplied Data 1b 1c 1d 10 • Participant’s results 1e 90 1f o CPD-supplied data 1g 20 1h 80 – Everyone analysed the same data sets 30 o 92% of returns used Rietveld method 70 Z in c ite (w t% ) o Note considerable spread in results 40 60

50 50

60 Corundum (wt%) Corundum 40

70 30

80 20

90 10

100 0 0 10 20 30 40 50 60 70 80 90 100 Fluorite (wt%)

11 | IanIan Madsen Madsen | | CSIRO TOPAS Mineral Training Resources Course– Level 1– Flagship 2013Level 1| || Quantitative2013 | Phase Analysis | DXC2014, Big Sky, Montana IUCr CPD Round Robin on QPA 0 1a 100 Participant Collected Data 1b 1c 10 1d 90 • Participant’s results 1e 1f o Participant collected data 1g 20 1h 80 o 75% of returns used a Rietveld method 30 70 o Spread of results is greater than Z in c ite (w t% ) for the CPD-supplied data 40 60 • What are the sources of error ? 50 o Methods ? 50 o Sample preparation ? 60 Corundum (wt%) Corundum 40 o Data collection ? 70 o Data analysis ? 30 80 20

90 10

100 0 0 10 20 30 40 50 60 70 80 90 100 Fluorite (wt%)

12 | IanIan Madsen Madsen | | CSIRO TOPAS Mineral Training Resources Course– Level 1– Flagship 2013Level 1| || Quantitative2013 | Phase Analysis | DXC2014, Big Sky, Montana IUCr CPD Round Robin on QPA 0 Test of Various Methods 1a 100 1b 1c 10 1d 90 • Samples analysed in CSIRO labs 1e 1f 20 o 3x replicates of 8 mixtures 1g 80 1h A range of methods used • 30 70 o 2x Rietveld packages Z in c ite (w t% ) 40 o 2x Single Peak methods 60 o 2x Iterative Least Squares 50 o 1x Mean Normalised Intensity 50 o 60 XRF (wt%) Corundum 40

• Summary 70 o Methods work OK 30 80 o Errors arise during 20 application of methods 90 10 100 0 0 10 20 30 40 50 60 70 80 90 100 Fluorite (wt%)

13 | IanIan Madsen Madsen | | CSIRO TOPAS Mineral Training Resources Course– Level 1– Flagship 2013Level 1| || Quantitative2013 | Phase Analysis | DXC2014, Big Sky, Montana

Sources of Errors

The sample - is it an ideal powder? Preferred orientation Particle statistics data

Sources of Errors The Sample - is it a Ideal Powder?

• Powder: A "solid containing small crystallites or particles that will flow when agitated", or similar, in accordance to the usual sense of the word in colloquial speech Sources of Errors The Sample - is it a Ideal Powder?

• Powder: A "solid containing small crystallites or particles that will flow when agitated", or similar, in accordance to the usual sense of the word in colloquial speech

• Powder: A "large number of crystallites and/or particles (i.e. grains, agglomerates or aggregates; crystalline or non-crystalline) irrespective of any adhesion between them" and thus can be a loose powder (in the sense of common language), a solid block, a thin film or even a liquid" *

• Ideal powder: A "virtually unlimited number of sufficiently sized, randomly orientated, and spherical crystallites" *

* EN-1330-11 (2007) Sources of Errors The Sample - is it a Ideal Powder?

• None of these examples represents an ideal powder • Sample preparation and presentation requires particular consideration

Sources of Errors

The sample - is it an ideal powder? Preferred orientation Particle statistics Crystal structure data

Sources of Error Preferred Orientation

Diffraction of an ideal powder

Diffraction of materials with preferred orientation Sources of Error Preferred Orientation

Example: • Blue: Preferred orientation • Red: No preferred orientation Sources of Error Preferred Orientation

• Most often seen in samples that contain crystallites with a platey or needle-like morphology • Extent of orientation can depend greatly on how the sample is mounted

Remedy? • Avoid software corrections • Try to improve sample preparation (e.g. backloading) and / or presentation (transmission) • Try to grind the sample • Do not destroy the sample (amorphization, phase transitions, ...) • Try different grinding techniques and perform grinding series to verify Sources of Error Preferred Orientation

• Bragg-Brentano geometry • Parallel or focusing beam Debye- Scherrer geometry using capillaries

Rotation parallel to the scattering vector does not minimize preferred orientation effects!

Sources of Errors

The sample - is it an ideal powder? Preferred orientation Particle statistics Crystal structure data

Sources of Error Particle Statistics

Diffraction of an ideal powder

Diffraction of a small number of crystallites ("spotiness effect") Sources of Error Particle Statistics

8 10 Debye cone of • Ideally some 10 - 10 diffracted beam crystallites in the beam • Ideally completely random orientation

Incident beam

Adapted from S. Misture, 2002 Sources of Error Particle Statistics

• Sample contains large crystallite(s) • A single particle can cause problems • Larger particles have a stronger tendency to preferred orientation • Too small number of crystallites • Sample only consists of a few crystallites or irradiated sample volume too small ( micro-diffraction) • Parallel beam geometry: Large irradiated sample volume but too few crystallites diffract Sources of Error Preferred Orientation

Example: • Blue: Particle statistics • Red: No particle statistics

Sources of Error Particle Statistics

Remedy? • Spotiness effects cannot be corrected by software • Spotiness and preferred orientation effects are often confused • Try to grind the sample • Do not destroy the sample (amorphization, phase transitions, ...) • Try different grinding techniques and perform grinding series to verify • If no 2D detector system is available, indexed Phi-scans can help to detect spotiness effects CPD-4 Phi Scans, 30° Steps

Zircon

Corundum

Sources of Errors

The sample - is it an ideal powder? Preferred orientation Particle statistics Crystal structure data

XYZ.3H2O – Calculated Pattern  Structure as read from database

460 Nesquehonite 100.00 % 440 ICDD Pattern ### Structure as read 420 from database: 400 2θ I/Io For S.G. = 14 380 13.65 100 software defaults to 360 14.58 2 P21/c 340 18.05 12 320 300 23.08 75 280 260 240 220

Sqrt(Counts) 200 180 160 140 120 100 80 60 40 20 0 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2Theta (deg) XYZ.3H2O XYZ.3H2O – Calculated Pattern  Space group set to P21/n

460 Nesquehonite 100.00 % 440 ICDD Pattern ### Correct setting for 420 this structure is 400 2θ I/Io P21/n 380 13.65 100 360 14.58 2 340 320 18.05 12 300 23.08 75 280 260 240 220

Sqrt(Counts) 200 180 160 140 120 100 80 60 40 20 0 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2Theta (deg) XYZ.3H2O – Calculated Pattern  Atomic Sites?

Atomic Number W = 74 O = 8

Site Names Atom Type in Site unimportant Critically important

Expected density = 1.84 g/cm3 Calculated density = 8.51 g/cm3 XYZ.3H2O – Calculated Pattern

105 Nesquehonite 100.00 % 100 ICDD Pattern ### Correct space 95 group setting 90 2θ I/Io 85 13.65 100 Correct site 80 14.58 2 scattering factors 75 18.05 12 70 23.08 75 65 60 55 50

Sqrt(Counts) 45 40 35 30 25 20 15 10 5 0 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2Theta (deg) XYZ.3H2O Database Entry

str space_group 14 ' Space group (HMS): P 1 21/n 1

a 7.7053 b 5.3673 c 12.1212 be 90.451

site mg1 x 0.25174 y 0.08872 z 0.15050 occ Mg 1.0 beq 1.0 site x 0.24393 y 0.13607 z 0.40940 occ C 1.0 beq 1.0 site x 0.26062 y 0.40719 z 0.06257 occ O 1.0 beq 1.0 site x 0.24408 y 0.20582 z 0.30895 occ O 1.0 beq 1.0 site x 0.25134 y 0.81598 z 0.02076 occ O 1.0 beq 1.0 site w1 x 0.52473 y 0.09140 z 0.15257 occ O 1.0 beq 1.0 site w2 x 0.98257 y 0.09667 z 0.14691 occ O 1.0 beq 1.0 site w3 x 0.27989 y 0.34792 z 0.83847 occ O 1.0 beq 1.0 Effect of Atomic Displacement Parameters  Yet more traps for the unwary

• ADPs correlate strongly with the Rietveld scale factor • Hence, ADPs used during analysis will impact on the final QPA • Many, many crystal structure database entries have arbitrary ADP values entered • 0.0, 0.5, 1.0 Å2 for all atoms – view with great suspicion

Intensity Variation with ADP Parameter

B = 0.0 Å2 1.0

0.8 B = 0.5 Å2

0.6

0.4 B = 1.5 Å2

Thermal Vibration Correction Vibration Thermal 0.2 B = 3.0 Å2

0.0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 2q

38 | IanIan Madsen Madsen | | CSIRO TOPAS Mineral Training Resources Course– Level 1– Flagship 2013Level 1| || Quantitative2013 | Phase Analysis | DXC2014, Big Sky, Montana Effect of Incorrect ADPs on Phase Abundances Sample 1G* – QPA vs Corundum ADP – ZMV method

42

40

38

‘Correct’ values for Al & O Beq 36 in corundum Δ wt% = 2.9wt% ≈ 9% relative Correlation of corundum 34 scale factor with:- Al Beq = 71% O Beq = 56%

Analysed Concentration (wt%) Concentration Analysed 32 Corundum Fluorite Zincite 30 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Beq (Å2)

* IUCr Round Robin on QPA – Sample 1G ≈ mixture of corundum (Al2O3), fluorite (CaF2) & zincite (ZnO)

39 | IanIan Madsen Madsen | | CSIRO TOPAS Mineral Training Resources Course– Level 1– Flagship 2013Level 1| || Quantitative2013 | Phase Analysis | DXC2014, Big Sky, Montana Summary

• Verify, verify, verify • Generate calculated patterns of individual phases • Check against • Data from pure sample of phase • ICDD database 7.© JuniCopyright 2016 Bruker Corporation. All rights reserved 41