Electron Microprobe Laboratory
Rhodes University’s Electron Probe Micro Analyzer (EPMA) Laboratory has a tradition in microanalysis since 1972, when a second-hand Camscan of Cambridge Instruments was installed. Our current 2011 model JEOL JXA-8230 EPMA is the third instrument, replacing a JEOL JXA-733 that had been purchased in 1985.
Electron microprobe analysis, as EPMA is commonly known, provides precise quantitative chemical analysis of elements in small volumes (~1 to 10 cubic micrometers or more) of solid specimens. Samples are polished sections of inorganic solids (e.g. natural rocks, mineral concentrates, gems, synthetic products, glasses, alloys, bones, fossils, etc.).
Our EPMA is setup to quantify all elements from Be to U using four automated wavelength-dispersive spectrometers (WDS) in point, line or grid analysis. In scanning mode medium- to small-scale element mappings can be produced. Microfabrics and zonation patterns of luminescent minerals can be investigated using a cathodo-luminescence detector.
We provide two analytical and three imaging modes of operation:
(i) Full quantitative mode: All detectable major and minor elements are quantified on a spot of
ca. 1 ?m diameter or larger. Trace elements are usually analysed with larger spot size.
(ii) Elemental distribution maps: Lateral variations of element concentrations are analysed at
high resolution in a two-dimensional maps.
(iii) Backscattered electron (BSE) imaging (compositional image).
(iv) Secondary Electron (SE) imaging (particle geometry and topography).
(v) Cathodo-luminescence imaging (variations in luminescence; quartz, zircon, carbonate, etc.).
JEOL JXA-8230 Superprobe
Purchased in late 2011 the instrument was commissioned in March 2012. NRF's National Equipment Programme and Rhodes University provided the funding for the new equipment.
Our EPMA has the following technical configuration:
- W electron gun.
- Computer automation operating through PC compatible JEOL software on a Windows XP platform.
- Four wavelength-dispersive spectrometers (WDS);
- One FCS type spectrometer with 4 crystals: LDE1, LDE2, TAP and PETJ.
- Two L type spectrometers with 2 crystals each: TAP, LiF (gas-flow counter) and LiFL, PETL (xenon counter), respectively.
- One XCE type spectrometer with 2 crystals: PETL, TAPL.
- Secondary-electron (SE) and backscattered-electron (BSE) detectors:
- Matrix corrections include ZAF and other methods
- “MiniCL” Gatan CL imaging system (visible range - 185 nm to 850 nm)
- Accelerating voltage: 0.2 to 30 kV
- Integrated visible-light microscopy: reflected, transmitted and cross-polarised light at 400 x magnification
- Auto-focus system for optimal sample positioning
Analytical services
- Carbon coating: Q150T E High Vacuum Evaporator
- Quantitative analysis of elements from F to U in inorganic solid materials as point or area analysis, line scans or grids.
- Quantitative element mapping
- Qualitative element analysis (WDS scan)
- High resolution (1-10 microns scale) BSE/SE imaging
- WDS scans to identify potential presence of elements down to trace amounts of tens of ppm
- Virtual WDS for testing various unusual calibrations
- EDS analysis is available via an Oxford Instruments Si(Li) detector system operating at Rhodes University’s Electron Microscopy Unit.
Analytical Costs
Please contact the Lab Manager.
Contact information
The laboratory is operated and managed by Dr. Deon van Niekerk.
Office: +27 (0)46 603 8316
e-mail: EPMA(at)ru.ac.za
Sample specifications
Standard size (46x26 mm) polished thin sections or polished cylindrical specimens (22 or 25 mm diameter) can be routinely analyzed. Large sample holders can accommodate custom sample sizes (maximum sample size: L100 x W100 x H50 mm).
Standards
- SPI 53 Mineral mount (serial XS)
- SPI 44 metal mount (serial NE)
- SPI 15 Rare Earth Pentaphosphates mount (serial GJ)
- SPI 23 mineral Custom mount (serial OG)
- JEOL 15 metal mount
Last Modified: Wed, 15 Jan 2020 11:14:49 SAST