X-ray Diffraction -Solving Problems with Phase Analysis

Joseph R. Swider, Ph.D.Senior Research Scientist

Uses of X-ray Diffraction

• phase identification of materials- different phases of materials with the same elemental composition can have extremely different properties

• commonly used for inorganics but many organics can be identified

• degree of crystallinity

Elemental and Phase

Identification

Phase: how are the atoms in a sample arranged?

TiO2

brookite

anataserutile

Elemental: What is the amount of each element in a sample?

TiO2

Mass Percent:60% Ti40% O

Phase IdentificationCalcium carbonate

CaCO3

calcitearagonite

XRD Theory

• X-rays acting as waves interfere with each other, constructively or destructively

• A bright reflection occurs when the path length difference is an integral number, or

nl = 2d sin q

q q

d

Powder XRD

single crystal

powder sample

XRD Instrumentation

X-ray source

sample

detection

CCD

film

XRD Data

International Centre for Diffraction

Data (ICDD)

Rigaku Micro-XRD

• Rotating anode

• Image plate detection

• Particles in the 100 -10µm size range

• 100µm beam size

Extraction and Mounting Particles

for micro-XRD

Other XRD Sample Mounting

Sample Submission

• What form is the sample?

– Bulk

– Powder

– Particle(s) to be extracted

• Will elemental analysis (EDS) be required?

• What data analysis will be needed?

– Comparison to ICDD

– Relative crystallinity

– Comparison to standards

Common Requests

Pharmaceutical verification

USP method <941>

Contamination identification

Corrosion products

Paint and pigments

Organics

Crystallinity

Limitations

**Quantitative XRD

**Percent crystallinity

Indexing

Single crystal analysis

Cryo or low temperature

In situ samples larger than ~1cm

Pigments and Paint

Phthalocyanine Blue

Synthetic Ultramarine Blue

Prussian Blue

Crystallinity

crystalline

semi-crystalline

amorphous

20 µm particle

10 µm mineral

Corrosion

Identification

Fresco Deterioration

• Several frescoes in a university hall were cracking with numerous accretions or spall

• Architectural conservators wanted to identify the spall-this would indicate what materials were underneath the painted layer and source the problem

• Samples of spall and from an intact fresco tested for the presence of gypsum

Sample 1 with spall

Sample 2 intact

Surface Contamination

Particles Removed from

Cross-Section Layers

High-Resolution Imaging and ElementalScanning Electron Microscopy with

Energy Dispersive X-ray Spectrometry (SEM/EDS)

Optical Properties and ImagingLight Microscopy (LM)

Organic ClassificationFourier-Transform Infrared Spectroscopy (FTIR)

Phase IdentificationX-ray Diffraction (XRD)

Organic QuantificationGas, Liquid Chromatography

Raman Microscopy

Raman Microscopy

Polarized Light Microscopy (PLM)

Cross-Section Evaluation

1

3

2

Test Painting

• Simple primed canvas with three layers of known pigment and media or commercial paint

• Sections taken and the layers analyzed for pigment and media by particle

• Not embedded in epoxy

Test Painting Area 1

Titanium white

Zincite

Barite

Rutile

Prussian Blue

1 23

Cadmium Yellow Light

Test Painting Area 3

3

2

1

Burnt Sienna in oilHematite, quartz, barite

Prussian Blue Hue watercolor

copper and iron phthalocyanines

indigo in linseed oil

barite

Architectural Lead Paint Identification

• Elemental (EDS or XRF) will identify Pb in paint structures or layers from samples but will not determine if it is white lead carbonate, the white pigment discontinued from industrial paints and known to be a health hazard

• Received samples as polished mounts with EDS map and Pb-rich layers to sample for identification of white lead carbonate

• Particles removed from chips or dust wipes can confirm the presence of white lead carbonate

Polished Mounts

8

10

1816

15th

century Spanish panel

painting

Painting

Sample

4

5

3

2

1

Sample 1, Layer 2

Layer 2 , blue

Particle from Layer 4

Joseph R. Swider, Ph.D.Senior Research Scientist

jswider@mccrone.com• (630) 887-7100

Thank you for joining us.

Layer 2, red

Sample 2, Layer 2