Claylab Applied Geology & Mineralogy X-ray diffraction A tool for material characterization and mineral quantification 1 Rieko Adriaens 23/01/2013

X-ray diffraction on mineral powders Divergence slit Detector- slit Tube Antiscatter- slit Sample Mono- chromator

Diffraction pattern Tube measurement circle focusing- circle θ θ 2 Detector Sample

Unique fingerprint for anorganic substances 4 a b c a = b = c === 90 o

crystalline Amorphous

Errors in XRD – analysis: Vendor competition Sample preparation Measurement Identification Quantification 6

Sample preparation: Classical approach Manual grinding using mortar & pestle Back/top loading of holder applying pressure 7

Classical approach: disadvantages Presence of coarse particles and bad loading cause several negative effects: – Extreme preferred orientation – Pattern shifts – Very poor reproducibility  Complex identification & wrong quantification 8

XRD pattern: Ideal case Classical approach: disadvantages – Preferred orientation & pattern shifts 9

Classical approach: disadvantages – Preferred orientation: Cleavage planes & prominent crystal faces 10 Halite Gypsum Mica Quartz

Classical approach: disadvantages – Preferred orientation & pattern shifts – Very poor reproducibility !!! 11

Bulk XRD – analysis Disadvantages impede accurate Q-XRD  Neccessity of standardized preparation procedures We need a procedure which makes sure that: -Particles should be finer than <50µm -Wet grinding instead of dry grinding -Particles are randomly oriented in the measurement holder -Sample surface should be smooth and perfectly flat -Reproducible & representative measurements 12

Standardized procedure after Srodon, 2001 Powder mixed with internal standard (ZnO, Al2O3, TiO2 ) Grinding media (Al2O3, Yttria stabilized Zr) Grinding agent: methanol/ ethanol McCrone micronizing mill (5min.) Side load filling / no pressure top load 13

Standardized procedure after Srodon, 2001  Good random orientation of crystallites obtained BUT can be improved by the making of spherical granules: use of Vertrel XF treatment, spray drying equipment, elvacite treatment,… 14 Kaolinite Portland cement

Standardized procedure: Validation 15 Classic methodology Renewed methodology

Standardized procedure: Validation 16 Much less preferred orientation Classic methodology Renewed methodology

Standardized procedure after Srodon, 2001  Allows accurate Q-XRD analysis 17

Other possibilities 18

[The Rietveld Method] Most powerful method for combined quantification and structure analysis Relies on the refinement of basic theoretical structures Minimize difference between calculated XRD pattern and measured XRD pattern

Rietveld refinement: procedure 1.Measure the diffraction pattern of the sample 3.Compare both patterns 4.Refine parameters and recalculate pattern 5.Draw info from the refined data (crystallite sizes / quantitative phase information / …) 2.Introduce reasonable starting models / values to calculate a diffraction pattern

What can be evaluated with a Rietveld refinement ? Example: Cement Fully amorphous blast furnace slag ZnO as internal standard

What can be evaluated with a Rietveld refinement ? 2.Crystallite Sizes / Strain – Absolute Crystallite sizes Useful for: – Process optimisation – Product characterisation – Product quality assesment Finer crystallites are prone to react faster (or to react better as catalysts, etc.) – Assessment of crystallite shape (in case of anisotropic peak size broadening) <10nm crystallites

What can be evaluated with a Rietveld refinement ? 3.Solid Solution – Example: Fe-rich Dolomite (CaMg(CO3)2) – Ankerite (CaFe(CO3)2) Change in lattice parameters as a function of the Fe-content With a Rietveld refinement; Lattice parameters and hence Fe-contents can be accurately determined Example: Fe-rich Dolomite/Ankerite in Sedimentary rock: Exact average formula: Ca(Fe 0,46 Mg 0,54 )(CO 3 ) 2 Fe-Dolomite

Practical information 24

Practical information 25 1st floor Ground floor XRD rooms Software computers

Practical information 26 Reservations

Practical information 27 Measurements overview list

Practical information 28 Technical support: Dirk Steeno 200C – General support: Rieko Adriaens 200E – Responsible professor: Jan Elsen 200E –

Questions / more information Contact 29