Home
Department of Earth Science

X-RAY LAB

Laboratory equipped for X-ray fluorescence spectrometry (XRF) and X-ray diffraction (XRD)

Main content

Instruments

X-ray fluorescence spectrometer Philips PW1404
X-ray fluorescence spectrometer Philips PW1404 was installed at the institute in 1989.

The instrument is a sequentiel spectrometer whit LIF200, LIF220, PE, GE, PX1 and PX5 crystals and a sample changer with 12 positions. The X-ray tube has a SC-W double anode.


X-ray diffraction instrument Philips PW 1700

X-ray diffraction instrument Philips PW 1700, have a sample changer with 40 positions, automatic divergensslitt, Cu X-ray tube and monochromator

 

Techniques


X-ray fluorescence spectrometry - XRF

Wavelength-dispersive x-ray fluorescence spectrometry - XRF - is a non-destructive analytical technique used to identify and determine the concentrations of the elements present in solids, powders and liquids. XRF is capable of measuring all elements from beryllium (atomic number 4) to uranium (atomic number 92). When a specimen is irradiated using a beam of sufficiently short-wavelength X-ray radiation, a characteristic X-ray spectra can be observed from the excited sample. Utilizing high intensity X-ray tubes, sensitive detectors, and suitable X-ray optics the XRF is fast, low cost quantitative analytical method. It might be noted that the detection limit is dependent on the peak-to-ground ratio of the spectral lines but the method has a detection limit for most of the elements at approximately 5 ppm.

X-ray diffraction (XRD)
X-ray diffraction is a versatile, non-destructive analytical technique for identification and quantitative determination of the various crystalline compounds, known as 'phases', present in solid materials and powders.

Identification is achieved by comparing the x-ray diffraction pattern - or 'diffractogram' - obtained from an unknown sample with an internationally recognised database containing reference patterns for more than 70,000 phases.

Modern computer-controlled diffractometer systems use automatic routines to measure, record and interpret the unique diffractograms produced by individual constituents in even highly complex mixtures.

Crystal lattice
xrd_ht2A crystal lattice is a regular three-dimensional distribution (cubic, rhombic, etc.) of atoms in space. These are arranged so that they form a series of parallel planes separated from one another by a distance d, which varies according to the nature of the material. For any crystal, planes exist in a number of different orientations - each with its own specific d-spacing. When illuminated by an x-ray source, crystalline material will generate x-ray diffraction peaks. The peak positions are described by the crystal unit cell parameters, and the peak intensities are given by the placement of the atoms in the unit cell. The peak widths are a result of two parameters, finite crystallite sizes and micro-stress within the crystallites. As such, the parameters that define different a crystal structure can be simply accessed from an x-ray diffraction pattern. Each mineral type is defined by a characteristic crystal structure, which will give a unique x-ray diffraction pattern, allowing rapid identification of minerals present within rock or soil sample.

When a monochromatic x-ray beam with wavelength lambda is projected onto a crystalline material at an angle theta, diffraction occurs only when the distance travelled by the rays reflected from successive planes differs by a complete number n of wavelengths.

Diffraction - Bragg's Law
By varying the angle theta, the Bragg's Law conditions are satisfied by different d-spacings in polycrystalline materials. Plotting the angular positions and intensities of the resultant diffracted peaks of radiation produces a pattern which is characteristic of the sample. Where a mixture of different phases is present, the resultant diffractogram is formed by addition of the individual patterns.

 

Scientific responsible:

 office , 3. floor

Technical responsible/contact:

Ole Tumyr office 3115, 3. floor


The X-ray lab is located in the second floor of the Department of Science building (Realfagbygget), the door number 2156