材料分析方法英文ppt
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Electron Probe Micro AnalyzerKai Chen Nhomakorabea1
EPMA
• Narrow sense: WDS: wavelength dispersive X-ray spectroscopy EDS: energy dispersive X-ray spectroscopy • Broad sense: SE, BSE, EBSD (electron backscatter diffraction), CL(cathodoluminescence), WDS, EDS • We will focus on WDS and EDS: both are nondestructive, high spatial resolution, for elements from atomic number 5 and higher (best for Z>10), works well for metals, alloys, ceramics, and glasses • They are similar but different • EDS can also be used in TEM
Difference: 1. SDD has better counting rate 2. Better energy resolution 5 3. Peltier (thermoelectric) cooling
Compare WDS and EDS
• WDS has higher sensitivity • WDS has better energy resolution • If you only care about one element, you can use WDS for 2D scan • EDS is much faster (can acquire a full spectrum of in a few second) • EDS is more suitable for 1D/2D scan
2
EPMA
1. EPMA comes from XRF 2. Knowledge of characteristic x-rays 3. Need an incident beam of electrons 4. Ip needs to be high 5. Most suitable for a sample from mm to mm 6. WDS and EDS are distinguished by detector
12
Broad sense of EPMA
13
6
Sensitivity
EDS
WDS
7
Energy resolution
Yellow peaks: EDS Grey peaks: WDS
WDS
8
Applications
• Spot mode, 1D mode, 2D mode • Qualitative vs Quantitative
9
EDS spectrum
10
Element maps
11
Quantitative
• Not good if Z<11 • Need to calibrate Z (atomic number), A (absorption), and F (secondary fluorescence) • Best precision ±5%
~1-2 mm
~2-5 mm
3
WDS
Experimental setup: Theory:
2d sin q l
2d sin q l
Known d, measure q, calculate l
4
EDS (EDX, XEDS)
Si drift detector
Si (Li) detector
EPMA
• Narrow sense: WDS: wavelength dispersive X-ray spectroscopy EDS: energy dispersive X-ray spectroscopy • Broad sense: SE, BSE, EBSD (electron backscatter diffraction), CL(cathodoluminescence), WDS, EDS • We will focus on WDS and EDS: both are nondestructive, high spatial resolution, for elements from atomic number 5 and higher (best for Z>10), works well for metals, alloys, ceramics, and glasses • They are similar but different • EDS can also be used in TEM
Difference: 1. SDD has better counting rate 2. Better energy resolution 5 3. Peltier (thermoelectric) cooling
Compare WDS and EDS
• WDS has higher sensitivity • WDS has better energy resolution • If you only care about one element, you can use WDS for 2D scan • EDS is much faster (can acquire a full spectrum of in a few second) • EDS is more suitable for 1D/2D scan
2
EPMA
1. EPMA comes from XRF 2. Knowledge of characteristic x-rays 3. Need an incident beam of electrons 4. Ip needs to be high 5. Most suitable for a sample from mm to mm 6. WDS and EDS are distinguished by detector
12
Broad sense of EPMA
13
6
Sensitivity
EDS
WDS
7
Energy resolution
Yellow peaks: EDS Grey peaks: WDS
WDS
8
Applications
• Spot mode, 1D mode, 2D mode • Qualitative vs Quantitative
9
EDS spectrum
10
Element maps
11
Quantitative
• Not good if Z<11 • Need to calibrate Z (atomic number), A (absorption), and F (secondary fluorescence) • Best precision ±5%
~1-2 mm
~2-5 mm
3
WDS
Experimental setup: Theory:
2d sin q l
2d sin q l
Known d, measure q, calculate l
4
EDS (EDX, XEDS)
Si drift detector
Si (Li) detector