P AUL SCHERRER INSTITUT
                                                  Technology Transfer  R&D Services
            Neutron Powder Diffraction
            Investigation of crystal structures
            Introduction                                                                                                          Figure 2: HRPT: Powder 
                                                                                                                                  diffractometer.
            X-rays vs. Neutrons
            For many decades X-ray powder diffraction 
            (XRD) has been an established and versatile 
            tool for manifold applications in material 
            science and engineering. It is well known 
            as a rapid analytical method, used for both 
            routine examination and scientific charac-
            terization of crystalline materials. 
                Neutron powder diffraction in terms of 
            its principles of operation is similar to X-ray 
            diffraction. Contrary to X-rays, however, 
            which interact primarily with the electron 
            cloud surrounding each atom of a given              The extracted information is in many  Physical properties gained
            material, most scattering of neutrons occurs    cases unique compared to that obtained 
            at the atom nuclei, thus providing comple-      from conventional X-ray diffraction tech-       The most common information typically 
            mentary information not accessible with  niques, because neutrons are sensitive to              extracted from a neutron powder diffraction 
            X-rays.                                         low atomic number materials, such as Hy-        experiment includes the symmetry of crys-
                The neutron furthermore carries a mag-      drogen and Boron, and capable of distin-        tal lattices, the dimensions of the unit cells 
            netic moment, which makes it an excellent       guishing between elements with adjacent         of the crystal structures and the elemental 
            probe for the determination of magnetic  atomic numbers, such as Iron and Cobalt,               composition thereof. Additionally, the frac-
            properties of matter.                           Isotopes of the same element, or element        tional coordinates and occupation factors 
                In the majority of cases, diffraction is    groups whose atomic numbers are wide  of the atoms within the unit cell are ex-
            the main mechanism of the interaction of        apart, such as Palladium and Hydrogen  tracted with typically very high precision, 
            the neutron with matter. This is why powder     (Deuterium). For these materials systems        providing reliable information on the in-
            diffraction experiments are perhaps the  ,neutron powder diffraction is ideally suited          teratomic bond distances, angles and ther-
            most straightforward among all neutron  to addressing the shortcomings of conven-               mal displacements of atoms. 
            scattering techniques.                          tional XRD methods.
                                                                                                            Finally, microstructure parameters charac-
                                                                                                            terizing the grain size distributions and 
                                                                                                            microstresses in the crystal lattice may also 
                                                                                                            be determined.
                                                                                                            Applications
                                                                               Figure 1: Structual 
                                                                               determination of             Neutron powder diffraction is most widely 
                                                                               orthorhombic RbFeO  – 
                                                                                                    2       used in the fields of crystallography, min-
                                                                               Rietveld refinement plot     eralogy, geochemistry, solid-state physics, 
                                                                               of the HRPT data collected   chemistry, material science & engineering 
                                                                               at T=1.5K: both crystal 
                                                                               and magnetic structure       and biology. Some materials systems, spe-
                                                                               refinement.                  cifically accessible and predestined to be 
              analyzed with this technique, are high-
              lighted below:
              •	 Metallic	alloys
              •	 Powdered	minerals
              •	 Ceramics
              •	 Isotope-substituted	materials
              •	 Low	atomic	number	materials
              •	 Hydrogen	storage	materials	
              •	 Antiferromagnetic	and	ferromagnetic	
                 materials
              Neutron powder diffractometers 
              at SINQ
              Neutron diffraction experiments are carried 
              out using sophisticated modern instru-
              ments located at powerful neutron sources, 
              such as nuclear reactors or spallation (ac-
              celerator-type) sources. Among other large-
              scale facilities, PSI operates the Swiss spal-         Figure 3: The DMC powder diffractometer is also appropriate for the investigation of magnetic 
              lation neutron source SINQ1, which  phenomena.
              encompasses an up-to-date park of neutron 
              scattering instruments. 
                  Among these, two neutron powder dif-               The table below details the key operational            Please feel free to ask us for further details.
              fractometers,	DMC2                   3
                                       and HRPT , are high-          characteristics	of	the	DMC	and	HRPT	instru-
              lighted below:                                         ments. Individual sample environment set-
                                                                     ups are possible on demand.                            1 http://sinq.web.psi.ch/
              DMC                                                                                                           2 http://sinq.web.psi.ch/dmc
              The	high-intensity	diffractometer	DMC	is	               Properties          DMC            HRPT               3 http://sinq.web.psi.ch/hrpt
              mainly designed for studies of phase tran-              Wavelength          2.3–6.0 Å      0.94–2.41 Å        4 https://duo.psi.ch/duo/,
              sitions and the detection of weak or fast               Scattering range    80° (400       160° (1600          http://sinq.web.psi.ch/sinq/sinq_call.html
              processes.	DMC	provides:                                                    channels)      channels)
              •	 high	intensity	for	weak	scattering	                  Best resolution     ≥ 0.006        ≥ 0.0009
                 materials or small samples                           ∆d/d
              •	 access	to	low	scattering	angles,	needed	             Temperature         110mK–1400 K  
                 for magnetic structure determination                 range, sample       (–273°C…1127°C)                      Contact 
                                                                      Magnetic field,     ≤ 4 T (vertical), ≤ 2 T              Dr. Denis Sheptyakov, 
              HRPT                                                    sample              (horizontal)                         Dr.	Lukas	Keller 
                                                                                                          3), 
              Complementary	to	DMC,	the	diffractometer	               Hydrostatic pres-   1.5 GPa (few cm                      Laboratory	for	Neutron	Scattering,	 
                                                                                                              3
              HRPT is designed for high-resolution neu-               sure, sample        10 GPa (few 10 mm )                  ETHZ & PSI
              tron powder diffraction studies with thermal            Beam size           Up to 5 cm (h)  x 1 cm (w)
              neutrons.                                                                                                        Tel. +41 (0)56 310 30 70  
                                                                                                                               Tel. +41 (0)56 310 40 07
              HRPT provides:                                         Example                                                   Email: Denis.Sheptyakov@psi.ch   
              •	 very	high	resolution	over	a	large	                  A typical HRPT diffraction pattern and the re-            Email:	Lukas.Keller@psi.ch
                 scattering angle range                              sulting crystal structure are shown in figure 1.          Technology Transfer PSI
              •	 high	suitability	for	advanced	structural	                                                                     Tel. +41 (0)56 310 27 22 
                 determination                                       Contact us                                                techtransfer@psi.ch
              The broad range of research topics investi-            Both,	the	HRPT	and	DMC	diffractometers	                   Paul Scherrer Institute
              gated	at	DMC	and	HRPT	is	complemented	                 are open to users from the world-wide sci-                5232 Villigen PSI, Switzerland 
              by a large collection of sample environ-               entific community through the user-access                 Tel. +41 (0)56 310 21 11
                                                                               4
              ments, covering an extremely wide range                program , as well as for scientific coopera-              www.psi.ch
              of pressures and temperatures.                         tion with industry.                                                                                            NUM-F08-D-10, 9.3.2010