JEOL JXA 8230 Electron Microprobe
The electron microprobe (electron probe microanalyzer, EPMA) is an instrument that enables quantitative chemical analysis of solid samples at the micrometre scale. With an electron microprobe, it is possible to determine the concentration of elements from B to U, with precisions on the order of 2% and detection limits of several hundred parts per million (ppm). It also allows line profiles and two‑dimensional concentration distribution maps to be obtained.
The electron microprobe uses a monoenergetic electron beam focused on the region of interest of the sample; as a result of electron–matter interaction, characteristic X‑rays are emitted. X‑ray intensities are recorded by wavelength‑dispersive spectrometers (WDS) and converted into concentrations through the combined use of reference standards and matrix‑effect corrections.
Equipment Features
• 5 WDS spectrometers:
- CH1: FCS type, 4 crystals: TAP, PETJ, LDE1, LDE2; gas‑flow proportional counter
- CH2: XCE type, 2 crystals: PETJ, TAP; gas‑flow proportional counter
- CH3: H type, 2 crystals: TAPH, LDE5H; gas‑flow proportional counter
- CH4: H type, 2 crystals: LiFH, PETH; sealed Xe proportional counter
- CH5: L type, 2 crystals: LiFL, PETL; sealed Xe proportional counter
• 1 SDD‑type EDS spectrometer, UTW window with variable aperture
• 1 EVACTRON plasma cleaner coupled to the pre‑camera
• Liquid‑nitrogen trap (LNT) anti‑contamination system
• Optical microscope with transmitted light
Technology Applications
• Determination of mineral chemistry and natural glass chemistry for rock classification, identification of alteration processes and mineral deposit genesis, and establishment of rock‑forming conditions (geobarometers, geothermometers).
• Identification and study of compositional variations in minerals, especially those associated with very slow diffusion processes. Analysis of fine mineral intergrowths (e.g., small exsolution lamellae) that reveal the thermal history and origin of crystals.
• Determination of the composition of experimentally produced minerals and glasses, and their application to phase‑diagram construction, thermodynamic model calibration, and determination of kinetic constants (e.g., diffusion coefficients).
• Acquisition of two‑dimensional distribution maps to locate economically relevant elements or to understand mechanisms and episodes of crystal growth and dissolution.
• Study of micro‑zoning in minerals such as zircon or monazite for geochronological applications.
• Identification of rare and/or new mineral phases of strategic interest.
• Study of glassy microinclusions in essential rock‑forming magmatic minerals (olivine, pyroxene, feldspars, and quartz).
• Study of inhomogeneous and/or zoned glassy or amorphous matrices and their application in volcanic hazard assessment.
• Characterization of microstructural phases and precipitates (at the micrometre scale) in alloys, metals, steels, ceramics, and advanced materials.
• Characterization of metallic phases and carbides in coatings produced by thermal spraying.
• Analysis of the composition and thickness of thin films and multilayers.
• Characterization of crystalline laser and nonlinear materials for photonic applications.
• Study of ageing in metallic alloys (solid‑state reactions) and failure analysis (early microstructural changes in materials).
Location
The JEOL JXA 8230 microprobe is managed by the Electron Microscopy and Related Techniques Unit and is located on the Diagonal Campus, in the main building of the CCiTUB.