X-ray diffraction (english version)

(update February 28th 2023)

Person in charge
Pierre-Emmanuel PETIT

Thomas FOURNIER
Jonathan HAMON

X-ray diffraction (XRD) is an elastic scattering technique, i.e. without loss of photon energy (unchanged wavelength), which gives rise to interferences. A distinction is made between single crystal and powder diffraction techniques. XRD is also a powerful technique to characterize thin films.

Applications

Single crystals (four-circle goniometer in Kappa geometry):

• crystal structures
• Low and moderate temperature phase transitions (for temperaturesranging from 90K to 500K)

Powders (Bragg-Brentano or Debye-Scherrer geometries):

• identification of crystallized phases
• quantitative determination of crystalline (possibly /
• determination
• crystallite size / microstrain (studies based on diffraction peak
• phase transitions at high temperatures / kinetics of these transitions
• operando studies (electrochemistry)
• characterization of the local of amorphous or poorly crystallizedmaterials (PDF studies)

Thin films (Bragg-Brentano geometry, grazing incidence diffraction or “ω-scan”):

• identification of crystalline phases
• microstructure
• texture (minimalist version: usea “rocking curve” type scan, alsocalled “omega-scan”)

The fleet consists of 8 machines,themost recentones being,on the whole, more versatilethan the older ones, which remain in a more specialized use:

Single crystal diffractometers:

• Rigaku Synergy S
• Nonius KappaCCD

Powder and Thin Film Diffractometers:

• Bruker D8 A25 “Da Vinci”
• PanalyticalX'Pert pro
• 2 Bruker D8 Series II: “Sample Changer” and “Chamber”
• Siemens D5000
• INEL XRG3500

Diffractometers for single crystals:

These two devices, housed at the Lombarderie site of IMN, are also used by CEISAM, and are accessible from outside under certain conditions.

Rigaku Synergy S Diffractometer

This apparatus, installed at IMN in 2020, is equipped with a microsource tube with a Mo anode (with its Montel-type focusing optics), a Hypix6000 hybrid pixel Si detector and a nitrogen cryogenic system (Oxford Cryosystems 800+) that allows the temperature of the crystal to be varied from 90 K to 500 K. It combines the advantages of a microsource (high diffracted intensity with small crystals) with the excellent signal-to-noise ratio provided by a latest- generation hybrid pixel Si detector.

The cost of the diffractometer (300 k€) was financed by:

Nonius KappaCCD Diffractometer

This apparatus, installed at the IMN in 2002, is equipped with a "classic" Mo anode X-ray tube, a "Princeton" CCD detector and a nitrogen cryogenic system (Oxford Cryosystem 700), allowing to reach the temperature range 90 K-373 K. The now outdated characteristics of its detector (notably its high readout noise) make it a second choice device. Nevertheless, it has been maintained for the time being and is fully functional.

Diffractometers for powders and thin films:

Bruker D8 A25 « Da Vinci » Diffractometer

Equipped with a second-generation Cu anode tube Si detector ("LynxEye XE") and numerous accessories (motorized slit, multilayer parabolic mirror, motorized XYZ table...), this θ/θ geometry device is very versatile (manufactured in 2013 and installed at the IMN site Lombarderie in 2020) and allows many applications:

• the energy resolution of the detector allows to avoid the X-ray fluorescence of samples containing Fe or Co, whatever the acquisition geometry used (Bragg-Brentano, parallel beam...);
• sits multi-layer mirror and radial Soller slits make it possible to study with a parallel beam massive samples that are not very regular and that one does not wish to polish or grind (non-destructive analysis). It is possible to envisage a fairly coarse spatial resolution (of the order of a millimeter);
• the multi-layer mirror, radial Soller slits and motorized table allow for grazing incidence studies of thin film samples;
• it is also possible to perform X-ray reflectometry using the motorized table, the multilayer mirror and appropriate slits;
• a stand to install electrochemical cells for operando studies.

Panalytical X’Pert pro Diffractometer

This apparatus, installed in 2009 at the IMN Chantrerie site, is also versatile, and is equipped with a first-generation Si strip detector ("X’Celerator"), whose energy resolution does not allow for the efficient removal of fluorescence radiation from Fe or Co. The speed of acquisition allowed by this detector allows in most cases to acquire excellent quality patterns in Bragg-Brentano (θ/θ) mode:

• a sample changer allowsthe acquisitiondiagrams ofa largenumber of powdered ormassive samples of small volume;
• a suitable sample holder allows the study of larger volume bulk samples and the accommodation of electrochemical cells (operando studies);
• an Anton Paar HTK1200N furnace for high temperature studies (T<1200°C, in air or neutral atmosphere).

Solid specimens of any size should have a flat surface (rough polishing may be sufficient). Otherwise, the use of the D8 "Da Vinci" described above should be considered.

Bruker D8 Série II Diffractometer « sample changer »

This apparatus, installed in 2006 at the IMN Lombarderie site, is equipped with a Cu anode tube and a first generation 1-D Si strip detector ("LynxEye"). It is also equipped with a Ge monochromator (111) placed at the exit of the tube stand, which makes it possible to obtain pure Cu K1 radiation. The Ge monochromator has advantages for powders with large crystallographic unit cells and/or low symmetry, as well as for Bragg-Brentano (θ/2θ) mode studies of thin-film samples deposited on single-crystal substrates.

This apparatus, not very versatile but equipped with a 90-position sample changer, is specialized in the acquisition in Bragg-Brentano mode of powder or massive but small samples, or samples deposited in thin layers on a monocrystalline or amorphous substrate. Its detector offers excellent performance except for samples containing Fe or Co, whose X-ray fluorescence is poorly filtered by the detector. It is also possible to install an airtight cell. This apparatus, the most used of the X-ray equipment, is often close to saturation, and allows the acquisition of about 2300-3000 patterns per year. It is widely open to external users, and several laboratories in Nantes (CEISAM, LPG, Arc’Antique, Université Gustave Eiffel Nantes) use it regularly.

Bruker D8 « chamber » Diffractometer with Anton Paar HTK 1200N furnace

This instrument, installed in 2006 at IMN (Lombarderie site), is equipped with a Cu or Mo anode tube, a motorized divergence slit and a fast 1-D gas detector ("Vantec"). The acquisition geometry is Bragg-Brentano θ/θ.

It works by campaigns and allows to install:

• a Cu anode tube and the Anton Paar HTK1200 N high temperature chamber (T<1200 °C, exclusively under air or neutral gas)
• a Cu anode tube and the Anton Paar XRK 900 high-temperature chamber (T<900 °C, reducing and/or humid atmosphere, vacuum - see the photograph of this instrument and more details on these chambers);
• an adapter support for electrolytic cells (operando studies);a Mo tube for PDF acquisition campaigns in Bragg-Brentano mode. This type of study, also known as total scattering, allows to investigate the local order of amorphous or poorly crystallized compounds.

Siemens D5000 Diffractometer

This apparatus, in Bragg-Brentano θ/θ geometry, is equipped with a Cu anode tube, a point detector (a scintillator) and a graphite secondary monochromator.

Advantages: easy access - no limitation for minimum angle (large unit cells) - filters X-ray fluorescence (samples containing Fe or Co).

Disadvantages: relatively long acquisition time (1 night). Presence of Cu Kα2 radiation - Despite these disadvantages, this device is still used (mainly because of its easy access), and is kept operational.

INEL XRG3500 Diffractometer

This instrument is dedicated to capillary diffraction in Debye-Scherrer geometry. It is equipped with a Cu anode tube, a primary monochromator (quartz) and a position-sensitive gas detector, allowing simultaneous acquisition over a 120° angular range.

Advantages: small quantities - air sensitive samples - relatively small minimum angle - no Kα2 radiation - relatively fast acquisition.

Disadvantages: absorbent and/or fluorescent samples. As it is the only apparatus in the laboratory that allows the use of capillaries, it remains indispensable despite its great age (apparatus installed in 1988).

Anton Paar XRK900 Chamber

Ancillary equipment for powder diffractometers:

• High temperature chambers :

  Two Anton Paar HTK1200 N chambers (T < 1200 °C, neutral atmosphere or under air), installed part-time respectively on the Bruker D8 “Oven” (Lombardy site) and the Panalytical X’pert pro (La Chantrerie site). These chambers do not allow for working under humid air.

  An Anton Paar XRK 900 chamber (T < 900°C), installed (alternately) on the Bruker D8 “oven”. This chamber is complementary to the other chambers, as it allows work to be carried out in a reducing atmosphere (a 5% H2/N2 mixture) and/or in a humid atmosphere.

• Sealed cells for air sensitive samples. Can be used on the Bruker D8 “Autosampler” and Bruker D8 “Da Vinci”.

• Electrochemical cells adaptable on the Panalytical X’pert Pro (at La Chantrerie) and on the Bruker D8 “Oven” and D8 “Da Vinci”. Not accessible outside IMN.