材料分析方法英文ppt.ppt

Electron Probe Micro AnalyzerKai Chen1EPMA Narrow sense:WDS: wavelength dispersive X-ray spectroscopyEDS: 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 non-destructive, high spatial resolution, for elements from atomic number 5 and higher (best for Z10), works well for metals, alloys, ceramics, and glasses They are similar but different EDS can also be used in TEM2EPMA31-2 mm2-5 mm1. EPMA comes from XRF2. Knowledge of characteristic x-rays3. Need an incident beam of electrons4. Ip needs to be high5. Most suitable for a sample from mm to mm6. WDS and EDS are distinguished by detectorWDS4Known d, measure q, calculate lTheory: Experimental setup: EDS (EDX, XEDS)5Si (Li) detectorSi drift detectorDifference:1. SDD has better counting rate2. Better energy resolution3. Peltier (thermoelectric) coolingCompare 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 6Sensitivity 7EDSWDSEnergy resolution 8WDSYellow peaks: EDSGrey peaks: WDSApplications Spot mode, 1D mode, 2D mode Qualitative vs Quantitative9EDS spectrum10Element maps11Quantitative Not good if Z11 Need to calibrate Z (atomic number), A (absorption), and F (secondary fluorescence) Best precision 5%12Broad sense of EPMA13。