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The X-Ray Laboratory onboard the R/V JOIDES Resolution (Foc's'le deck) performs diffraction analyses of minerals and rock powders. The laboratory uses a Bruker AXS D4 Endeavor XRD (a.k.a. Bruker or D4) and a PANalytical Aeris XRD (a.k.a. Aeris) diffractometers (Figure 1).
Bruker-associated softwares. Associated software, EVA, DIFFRACplus and TOPAS, allow for powder diffraction analysis of minerals, including peak-matching and mineral and chemical compound identification. XRD scans from the Bruker can also be analyzed using HighScore (came with Aeris Panalytical XRD) software. The XRD Plus software (used for the Aeris measurements). The X-Ray lab provides scientists with a quick and reliable tool for mineral identification; particularly useful for identifying bulk mineralogy, clays, fine-grained minerals or mixtures of secondary minerals. In addition, XRD can be used to determine mineral proportion.
Figure 1. A. Bruker D4 Endeavor XRD. B. PANalytical Aeris XRD in the X-Ray lab
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Principle of X-Ray Diffraction
A mineral is a three-dimensional structure that forms a crystal lattice. When a focused X-ray beam is directed onto the crystal structure of a mineral, part of the beam is diffracted. X-rays are diffracted differently depending on the atomic composition and arrangement within the crystal lattice. Each mineral has a unique fingerprint that is determined based on a characteristic set of d-spacings (space between adjacent planes of atoms in the crystal lattice). This is a fundamental characteristic of minerals that allow mineral identification through X-ray diffraction. X-rays are generated in a vacuum tube and directed to a powdered sample, when the X-rays hit the powdered sample, they are diffracted onto a detector. The X-ray detector then converts the signal to a count rate. The angle between the X-ray tube, sample, and detector are varied during measurement to produce an X-ray scan . Using the angle between the X-ray tube, sample, and detector (2θ, which can be measured) and the wavelength of a generated X-ray beam (λ, which is known based on the material generating the X-rays), the scientist can determine the d-spacings by using Bragg's law (Figure 2):
nλ =
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2dsinθ
n = order of the diffracted beam
λ = wavelength of the incident X-ray beam
d = distance between adjacent planes of atoms (d-spacings)
θ = angle of incidence of the X-ray beamThe d-spacings generated by an X-ray scan provide the unique fingerprint of the mineral or minerals present in the sample.
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Figure 2. Bragg's law
References - Further reading
Cullity, B.D., 1978. Elements of X-Ray Diffraction, Second Edition. Addison-Wesley Publishing Company, Inc., Massachusetts.
Bish, D.L., and Post, J.E. (Editors), 1989. Reviews in Mineralogy Volume 20, Modern Powder Diffraction. The Mineralogical Society of America, Washington, D.C.
Books are available in the X-Ray lab upon request.
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Hardware
This section presents instrumental characteristics of the Bruker AXS D4 Endeavor X-ray diffractometer (XRD) in the X-Ray lab. For the Aeris, see the Aeris Advanced User Guide.
The Bruker is composed of:
- Goniometer
- X-ray source (sealed vacuum tube with line focus): on the JR, a Siemens ceramic X-ray tube KFL Cu-2K, 2.2 kW, 60 kV, 0.4mm x 12mm is used
- Tube housing (ceramic body that protects the tube and shields from X-rays)
- Mount
- Sample holders
- Vantec-1 detector
- Optics
- Slit systems
- Haskris water chiller for the X-ray tube
X-Ray Diffractometer
The Bruker AXS D4 Endeavor XRD can analyze powder, liquid,
Laboratory Apparatus
- Haskris water chiller for X-ray tube
- Cahn Model 29 or 31 microbalance
- Mettler-Toledo XS204 dual-balance system
- Powdering equipment:
- Agate mortar and pestle
- Mixer mills
- Shatterbox
- X-Press
- Glass bottles
- Sonic dismembrator
- Glass rod
- Glass beakers
- Pasteur pipette/eye dropper
- Centrifuge and centrifuge tubes
- Desiccator
- Labconco Freeze Dryer
Reagents
- Ethylene glycol (clay glycolation)
- 2 M HCl: 16.4% v/v (carbonate dissolution)
- Glacial acetic acid, 10% v/v solution (carbonate dissolution)
- Distilled (reagent) water (DI)
- 1% w/v Borax solution
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- Bruker AXS D4 Endeavor X-ray diffractometer (XRD)
- Goniometer
- X-ray source (sealed vacuum tube with line focus)
- Tube housing (ceramic body that protects the tube and shields from X-rays)
- Mount
- Sample holder
- Vantec-1 detector
- Optics
- Slit systems
X-Ray Diffractometer
The Bruker AXS D4 Endeavor XRD can analyze powder, liquid, and solid samples in a variety of sample holders. The sequence of the beam path is X-ray source > primary X-ray optics > sample > secondary X-ray optics > detectoroptics > detector (Figure 3).
Figure 3. Schematic drawing of the beam path of the Bragg Brentano geometry in the Bruker (from the D4 Endeavor User Manual).
The X-Ray radiation generated by the electron beam in the anode material (i.e., Cu for our instrument) of the X-ray tube hits the sample in the goniometer center and is diffracted by the crystalline properties of the sample (Figure 3). The diffracted radiation is detected by an X-ray sensitive detector and gives qualitative and quantitative results according to the properties of the sample (i.e., chemical composition and physical properties like crystallinity).
During the measurement of the characteristic diffraction pattern of a polycrystalline sample, the sample rotates with a constant angular velocity around the goniometer center (θ circle). Simultaneously to this θ rotation the detector rotates at double angular velocity around the goniometer center (2θ circle) and sample, respectively. The 2θ rotation is perpendicular to the measurement plane as well and concentric to the θ circle. In other words, the diffraction angle 2θ where the detector is positioned is the angle between the primary beam direction and the diffracted beam direction.
Goniometer
The goniometer has 2 circles: the theta (θ) circle, which sets the sample position, and the 2θ circle, which moves the detector. The position of the X-ray tube remains fixed. The goniometer center is defined by the concentric circle axes.
Component | Specification |
Measuring circle diameter | 401 mm |
Operating mode | Vertical, θ/2θ |
Max angular range | –8° < 2θ < 170° |
Smallest step width | 0.0087° |
Reproducibility of θ/2θ angle | ±0.0002° |
Absolute accuracy (θ/2θ) | <±0.005° |
Sample Holders
Sample holders for powdered XRD samples are steel or steel with a silicon or quartz spacer. The selection of a sample holder depends on the volume of sample to be analyzed.
circle axes.
Component | Specification |
Measuring circle diameter | 401 mm |
Operating mode | Vertical, θ/2θ |
Max angular range | –8° < 2θ < 170° |
Smallest step width | 0.0087° |
Reproducibility of θ/2θ angle | ±0.0002° |
Absolute accuracy (θ/2θ) | <±0.005° |
Amount of Powdered Sample | Sample Holder |
Large: 2.0 mm depth | Steel |
Medium: 1.8 mm depth | Steel |
Small:1.0 mm depth | Steel with quartz or zero-background Si spacer | Smallest (vein/vesicles, scrapings) | Slurry (see Sample Slurry/Smear Slide Mounting for Small Sample Amounts)
Detector
The VANTEC-1 detector features the fastest simultaneous recording of XRD patterns within a wide 2θ angular range. For powders, measurement time is reduced by a factor of up to 100 in comparison to other detectors.
Component | Specification |
Active area | 50 mm x 16 mm; 1600 pixels |
Max 2θ range covered | 12° at 435 mm diameter; 11° at 500 mm |
Usable wavelength | Cr–Kα to Mo–Kα |
Max local count rate | 400,000 cps |
Spatial resolution | <50 µm; >1600 channels |
Gas fill | 3.04 bar Xe-CO2; no external supply needed |
Power rating | 120 W |
Ambient temperature | 41°–104°F (5°–40°C) |
Operating temperature | 57°–93°F (14°–34°C) |
Relative humidity | Maximum 80 %, noncondensingnon condensing |
Detector Optics
- Detector window slits
- Debye slits
- Kβ filter: suppresses characteristic Kβ radiation
- Antiscatter slits: reduce primary air scatter, which influences diffraction background patterns
- Soller slits: reduce primary and secondary air scatter Window opening scales
- radiation
- Antiscatter slits: reduce primary air scatter, which influences diffraction background patterns
- Soller slits: reduce primary and secondary air scatter
- Window opening scales
Sample Holders
Sample holders for powdered XRD samples are steel or steel with a silicon or quartz spacer. The selection of a sample holder depends on the volume of sample to be analyzed.
Amount of Powdered Sample | Sample Holder |
Large: 2.0 mm depth | Steel |
Medium: 1.8 mm depth | Steel |
Small:1.0 mm depth | Steel with quartz or zero-background Si spacer |
Smallest (vein/vesicles, scrapings) | Slurry (see Sample Slurry/Smear Slide Mounting for Small Sample Amounts) |
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XRD Commander 
is the running software of the Bruker D4 XRD.
Two other softwares are needed to analyze the diffractograms obtained with the D4.
- DIFFRAC.SUITE.EVA, version 3.0 software for evaluation
(a more recent version, version 5.1, is also available
) - DIFFRAC.TOPAS version 4.2.0.1 software
for diffractogram analysis
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The instruments in the lab need to be turned on in this order: (1) HASKRIS water chiller and (2) D4 XRD. The HASKRIS cools the water supplied to the D4 to prevent the X-ray tube from overheating. Turning the D4 on prematurely could damage the X-ray tube.
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