ED-XRF: Principles and Applications · PDF fileED-XRF: Principles and Applications Justin...

ED-XRF: Principles and Applications

Justin Masone

Shimadzu Scientific Instruments

7 June 2016

AMC 2016 - UIUC

What is XRF?

• Analytical method to determine the elemental

composition of many types of materials

What is XRF?

• Analytical method to determine the elemental

composition of many types of materials

Fe 81.289%

Cr 17.0%

Mn 0.5%

Si 0.5%

Mo 0.3750

P 0.02%

440C

Stainless

What is XRF?

• Can be used to determine the thickness and

composition of layers, coatings, and platings.

Layer 1

15.156 μm

100% Cu

Base

100% Zn

What is XRF?

• Fast

• Accurate

• Non-destructive

What is XRF?

• Requires minimal sample prep

What is XRF?

• Sample form can be:

Powder Filter Paper

Solid Liquid

Types of XRF

First, some clarification…

X-Ray Fluorescence Spectrometry

Energy-Dispersive XRF

(EDXRF)

Wavelength-Dispersive XRF

(WDXRF)

Non-Dispersive XRF

(NDXRF)

What is ED-XRF?

Energy-Dispersive X-Ray Fluorescence

Energy-dispersive: Ability to discern the energies of x-rays

X-Ray: Form of energy; source of ionizing radiation

Fluorescence: Phenomenon of absorbing energy (short λ)

and subsequently emitting energy (longer λ)

Basis of EDX

Fluorescent

X-rays

1

2 3

4

5

6

Data Processing Unit

Pre-amp/DPP

Irradiating

X-rays

What are X-Rays?

X-rays are a kind of electromagnetic energy:

0.01 – 10 nm

0.125 – 125 keV

12 / 9

How Do X-Rays Interact with Matter?

When X-rays strike matter, some of them are absorbed and some

pass through

A consequence of absorption is that secondary X-rays are

generated, which are characteristic of that matter:

13 / 9

How Do X-Rays Interact with Matter?

14 / 9

How Do X-Rays Interact with Matter?

Degree of fluorescence

depends on:

• Thickness

• Density

• Sample material

X-ray penetration depth (Rh source):

Pb 25 μm

Fe 200 μm

H2O 3 cm Irradiating X-ray

Transmitted X-ray

ρd

Fluorescent X-ray

15 / 9

How Do X-Rays Interact with Atoms?

++++++

-

-

-

-

- -

-

-

++

-

-

-

-

-

-Irradiating

X-ray

Ejected

Electron

Fluorescent

X-ray

16 / 9

Types of Transitions

Ratios of fluorescent X-rays:

Kα : Kβ = 100:20

Lα : Lβ = 100:70-100

These are “Characteristic X-rays”

17 / 9

Energy of X-Rays

X-rays exhibit wave-particle duality. The wave characteristics are

expressed in wavelength (λ, nm), and the particle characteristics are

expressed in the form of a photon with a specific energy (E, keV).

λ

E

18 / 9

Energy of X-Rays: Example

++++++

-

-

-

-

- -

-

-

++-

Fe atom

Kα

=

(4.14 × 10−18𝑘𝑒𝑉 ∙ 𝑠) ×

(3.00 × 1017𝑛𝑚 ∙ 𝑠)

0.194 𝑛𝑚

19 / 9

Energy of X-Rays: Example

20 / 9

EDX Spectrum

21 / 9

EDX Data Output

List of elements

present, including

carbon as a balance

Amount present in

sample; can be

reported in various

units Type of analysis

Transition used for

quantitative

calculation

22 / 9

Analytical Range

23 / 9

Types of X-Rays

Characteristic X-rays• Discrete energies

• Energy out

Continuous X-rays• Variety of energies

• Energy in

• “Background”

24 / 9

Continuous X-Rays

In addition to fluorescence, an irradiating electron can be influenced by the attractive forces

of the nucleus and repulsive forces of the surrounding electrons without any actual collision.

In this case, the course of the electron is altered, which causes it to slow down and release

energy (an X-ray). This is called bremsstrahlung (braking radiation).

25 / 9

X-Ray Tube

X-ray tubes are <1% efficient

W

Rh over Cu

26 / 9

EDX System

X-ray tube

Filters

Collimator

C-MOS

camera

Detector

(SDD)

Sample

27 / 9

X-Ray Tube: Why Rhodium?

Why is rhodium used as the X-ray target?

• Rh K-rays are efficient at generating

fluorescent X-rays from heavy elements,

and the L-rays are efficient at generating

fluorescent X-rays from light elements

• Rh is rarely the subject of analysis

(however, Rh analysis is still possible)

28 / 9

X-Ray Tube: Scattered Radiation

Some of the X-rays from the tube do not generate fluorescent X-

rays when they strike the sample. Instead, they are scattered

within the sample. There are two types scattering radiation:

Compton Scattering: When the source characteristic X-rays (Rh) that strike the

material suffer from some energy loss (inelastic scattering)

Rayleigh Scattering: When the source characteristic X-rays (Rh) strike the sample

without any change in energy (elastic scattering)

29 / 9

X-Ray Tube: Scattered Radiation

Rayleigh

scattering

Compton

scattering

The intensity of the Compton scattering is

influenced by the material/density of the sample

30 / 9

X-Ray Tube: Scattered Radiation

• Samples with light elements give rise to high Compton scatter and low Rayleigh

scatter

• This is because they have more loosely bound electrons

• With very heavy elements, the Compton scattering disappears completely

Lead Plastic

31 / 9

Filters

We have learned that Rh X-rays contribute to the EDX spectrum, in terms of

characteristic X-rays, as well as continuous X-rays (background).

Sensitivity is low in these areas, so we introduce a filter to minimize the

source Rh and increase sensitivity:

32 / 9

Primary Filters

Filter #2 Filter #4 Filter #1

RhL line

Background from

continuous X-rays

RhK line

33 / 9

EDX Detector: SDD

Amptek XR-100FAST SDD is used in the EDX-7000/8000.

It is a High Performance Silicon Drift Detector.

X-rays from sample Be/C1 window ionize semiconductor material (high-purity

silicon) charge converted to voltage by FET (pre-amp) voltage converted to

digital count by DPP

34 / 9

EDX Detector: Si(Li) and Si-PIN

• Prior to high-performance SDDs, EDX utilized Si-PIN or Si(Li)

• These detectors are still common, but not in newer, “high end”

benchtop models

• High resolution• Must be LN2-cooled (-150 °C) to obtain

sufficiently low conductivity (e.g. best

resolution)

Si(Li)Si-PIN

• Moderate resolution and low count

rates (10 kcps), but is Peltier-cooled

35 / 9

EDX Detector: Si-PIN

• ~200 eV resolution (Mn-Ka)

• 32 μs peaking time

• P/B: 4000:1

36 / 9

EDX Detector: SDD

• 125 eV resolution (Mn-Ka)

• 4 μs peaking time

• P/B: 22,000:1

37 / 9

Optional Hardware

Analysis can be done in air, He atmosphere, or under vacuum.

Atmospheric Control

Solid - Air, Vacuum, or Helium

Liquid - Air, Helium

Powder - Air, Vacuum*, Helium

For elements lighter than Cl, analysis must be done under atmospheric control O2

and CO2 in the atmosphere absorbs the fluorescent X-rays

Sensitivity will increase for light elements

38 / 9

Optional Hardware: Vacuum Pump

— Vacuum

— Air

-Na

Ka

-Mg

Ka

-AlK

a

-SK

a

-RhL

a

-RhL

b1

-KK

a

-Ca

Ka

-SiK

a

-Ca

Ka

39 / 9

Optional Hardware: Helium Purge

Helium Purge

Analysis is done in a helium atmosphere. The instrument purges the detector window

and X-ray tube window.

40 / 9

Example Applications

Electrical/electronic materials RoHS and halogen screening

Thin-film analysis for semiconductors, discs,

liquid crystals, and solar cells

Automobiles and machinery ELV hazardous element screening

Composition analysis, plating thickness

measurement, and chemical conversion

coating film weight measurement for

machine parts

Ferrous/non-ferrous metals Main component analysis and impurity

analysis of raw materials, alloys, solder, and

precious metals

Composition analysis of slag

Mining Grade analysis for mineral processing

Ceramics Analysis of ceramics, cement, glass, bricks,

and clay

Oil and petrochemicals Analysis of sulfur in oil Analysis of additive elements and mixed elements

in lubricating oil

Chemicals Analysis of products and organic/inorganic raw

materials Analysis of catalysts, pigments, paints, rubber, and

plastics

Environment Analysis of soil, effluent, combustion ash, filters,

and fine particulate matter

Pharmaceuticals Analysis of residual catalyst during synthesis Analysis of impurities and foreign matter in active

pharmaceutical ingredients

Agriculture and foods Analysis of soil, fertilizer, and plants Analysis of raw ingredients, control of added

elements, and analysis of foreign matter in foods

Others Composition analysis of archeological samples and

precious stones, analysis of toxic heavy metals in toys and everyday goods

41 / 9

Application Notes

Screening Analysis with EDX-7000 Navi Software

Quantitative Analysis of Elements in Small Quantity

of Organic Matter by EDXRF

- New Feature of Background FP Method -

Quantitative Analysis of Cement by EDX-8000

Quantitative Analysis of Waste Oil by EDX-7000

TC Measurement and Elemental Composition

Analysis of Fly Ash

- Quantitation by TOC and XRF -

Quantitative Analysis of Tin (Sn) in Plastics by

EDXRF

Analysis of Aqueous Solution by EDX-LE

- Performance in Air Atmosphere -

Quantitative Analysis of Fluorine (9F) by EDXRF

Quantitative Analysis of Antimony (Sb) in Plastics by

EDXRF

Qualitative and Quantitative Analysis of Seafood by

EDXRF

EDXRF Analysis of Arsenic and Lead in Dietary

Supplement

QC Analysis of Magnesium Alloy Die Castings by

EDXRF

EDXRF Analysis of PM2.5 (Particle Matter)

EDXRF Analysis of Sulfur and Other Elements in Oil

EDXRF Analysis of Lead, Cadmium, Silver, Copper in

Lead-Free Solder Materials

Determination of Arsenic and Lead in Earth and Sand

Using EDXRF [JIS K 0470]

Comparison of Calibration Curves of Lead, Cadmium

and Chromium in Zinc Alloy and Copper Alloy

EDXRF Analysis of Lead, Cadmium, Mercury and

Chromium in Zinc Alloy

EDXRF Analysis of Chlorine in Irregularly Shaped

Plastic Samples

Analysis of Foreign Matter in Food Using EDX

EDXRF Analysis of Heavy Elements in a Toy and a

Cup

EDXRF Analysis of Chlorine in Plastic (PE) Materials

Analysis of Sulfur in Oil Using Energy Dispersive X-

Ray Fluorescence Spectrometer

Analysis of Foreign Matter Using CCD

EDXRF Analysis of Arsenic in Foods

42 / 9

Quantitative Analysis Results for Foreign

Matter by FP Method

(Ti and Zn are excluded from the

quantitative calculations.)

Analysis Example: Foreign Matter Adhering to a Plastic Extruded Part

—F

e K

b

—N

i K

a

—C

r K

a

—C

r K

a M

n K

b

—T

i K

a

—T

i K

b

—N

i K

b

—Z

n K

a

—Z

n K

b

—M

o K

a

Foreign matter

Clean area

—F

e K

a

Sample

Appearance

Red circle: Foreign matter

Blue circle: Clean area

Application: Foreign Matter Identification

43 / 9

MRL Application: Film Thickness

Results from XRD: 26 nm

44 / 9

MRL Application: Brick from

Annealing Furnace

45 / 9

MRL Application: Carrot-Orange

Juice

01/01MTS-50C-60s-1-He Thermal-1-72C-15s-He Control-1-He MTS-60C-30s-2-He

Al-U

3.0 4.0

[keV]

0.00

0.50

1.00

1.50

2.00

[cps/uA]

S Ka

RhLa

RhLb1

K Ka

K Kb BaLa

Na-Sc

2.0

[keV]

0.00

0.50

1.00

1.50

2.00

[cps/uA]

RhLa ESC

RhLb1 ESC

P Ka

S Ka

RhLa

RhLb1

AgLa

AgLb1 K Ka

K Kb

46 / 9

MRL Application: Strontium

Contamination

• MRL XRD system was

unable differentiate

what seemed like

Strontium from other

peaks in the material

• Confirmation by EDX

allowed the user to

pursue this

contaminant.

47 / 9

MRL Application: Hafnium

Contamination

• Hafnium was unexpected, but the contaminant was tracked down to

the chamber in which the sample was made

48 / 9

Additional Information

Additional Information:

http://www.ssi.shimadzu.com

Tom Wilhite

tjwilhite@Shimadzu.com

Ray Kern

rmkern@Shimadzu.com