Geology and Geophysics
YALE ELECTRON MICROPROBE & SEM LABORATORY
Kline Geology Laboratory Room 327, P.O. Box 208109, New Haven, CT 06520-8109 203-432-3181
NSF Instrument Upgrade (IF/EAR-0744154) and Yale University Fund Installation of JEOL JXA-8530F
The JEOL JXA-8530F (FEG) "Hyperprobe" now is installed; testing toward appropriate behavior and consistency continues. This electron probe microanalyzer (EPMA; aka electron microprobe analyzer, EMPA) permits imaging of features as small as 5-10 nanometers and quantitative analytical (chemical) resolution of features perhaps as small as 200 nm (~800 nm @10 kV). This analytical resolution applies to both quantitative analysis and extremely high-resolution chemical mapping. UPDATE: At present, our capabilities for microprobe analysis are complete, though some sporadic stability problems remain with software, communications, and beam current. We are accomplishing numerous sessions as time is available, including WDS quantitative work, electron imaging, EDS qualitative inspections, qualitative WDS scans, and sample chemical mapping (including WDS). Schedule updates and current constraints can be found here. Thanks for your interest, and please stay tuned for details...
|Information Contact, Jim Eckert||Current hourly usage rates|
|Current Microprobe Status||Vendors of Equipment in our Lab:|
|Yale Microprobe Training Course||JEOL JXA-8530F Electron Microprobe|
|Instrument Configuration||Emitech Carbon Evaporator||Upcoming SCHEDULE, Yale-Microprobe Calendar|
|Internal Links on this Page:||Quantitative Analysis||Links to Other Microprobe Information:|
|Appropriate specimens||Page of Other Microprobe Resources|
|Yale Microprobe Access|
Qualitative and semi-quantitative microscale chemistry can be assessed rapidly using EDS spectrometry. This can benefit phase identification and recognition of compositional variability in a sample. This allows rapid imaging and compositional mapping, as well as storage of images and data in readily transferable formats. With either the native JEOL acquisition software or with Probe for Windows, we also can accommodate integration of EDS data into the quantitative-analysis package.
Quantitative microscale chemical analysis, using wavelength dispersive spectrometry (WDS), requires both a stable, well-tuned instrument and standards for comparison that are both well characterized and appropriate for a given specimen. The JXA-8530F is proving to be a stable instrument most of the time, and the Yale suite of available standards is quite diverse and extensive. Typical operating conditions for the electron beam are an accelerating voltage of 15 kV beam currents of 5 to 20 nanoamps, and beam diameter of 5 to 10 microns. However, these parameters can be varied widely (0.5 - 30 kV, ~10 pA to ~1500 nA) to address various questions. Many of the Yale standards, a collection begun by Horace Winchell in the 1960's, are appropriate representatives of their mineral group. These generally high quality standards, which include both synthetic and naturally occurring varieties, have been graciously provided by a wide variety of esteemed scientists over several decades. Nonetheless, alternative standards for less traditional projects also can be applied.
Quantitative analysis can address all elements heavier than beryllium (boron and higher). Each analysis takes several minutes to count the X-rays and perform related calculations. Ultimate WDS detection limits for sodium and heavier elements are about 50 to 100 ppm (0.005 to 0.01 wt%, elemental); for lighter elements, the instrument is somewhat less sensitive. For most major elements, these truly quantitative microscale chemical measurements typically have accuracy and precision on the order of 1%. Comprehensive setups applied heretofore include a 33-element oxide setup, incorporating all REE with overlaps and interferences. Automated analysis allows the operator to assign locations for analysis during a session, then acquire data automatically (unattended) at those stored locations. Thus, the operator may concentrate on other tasks while the time-consuming X-ray counting and data reduction are completed. Data can be transferred via network or USB connections for rapid accommodation into reports and manuscripts.
For the Upcoming Schedule, Yale-Microprobe Calendar, click here