Structure determination at high pressures: X-ray diffraction

Transcription

1 Structure determination at high pressures: X-ray diffraction Julio Pellicer Porres MALTA Consolider Team Dpto. de Física Aplicada ICMUV, Univ. València, Spain 1

2 Outline XRD at high pressures Outline: - X ray diffraction at high pressures. - Special needs. - Synchrotron radiation. - EDXRD - ADXRD - Single crystal XRD - Examples. 2

3 XRD at high pressures Special needs Special needs of XRD high pressure experiments Which are the limitations imposed by high pressure to XRD? 1. Sample size. MSPD, ALBA ID27, ESRF 3

4 XRD at high pressures Special needs XRD at high pressures and synchrotron radiation Which are the limitations imposed by high pressure to XRD? 2. Absorption from anvils and sample environment. Mn K kev Ti K kev Cu K kev 4

5 XRD at high pressures Special needs XRD at high pressures and synchrotron radiation Which are the limitations imposed by high pressure to XRD? 3. Limited angular range Ej: XRD spectrum simulations. CuAlO 2 (R-3m, a=2.86å, c=16.96å). l= Å, E=17.5 kev (Mo K ) 10 reflections l= Å, E=30 kev 46 reflections An intense, highly collimated, hard (20-50 kev) x-ray beam is needed 5

6 Outline Synchrotron radiation Outline: - X ray diffraction at high pressures. - Special needs. - Synchrotron radiation. - EDXRD - ADXRD - Single crystal XRD - Examples. 6

7 XRD at high pressures Synchrotron radiation Synchrotron Bending magnet Wiggler Undulator 7

8 XRD at high pressures Synchrotron radiation Synchrotron Radiation -Main advantages: - Brilliance - Wide wavelength range, from the IR to hard x-rays. - Linear and circular polarization. - Possibility of a time pulsed source. 8

9 XRD at high pressures Synchrotron radiation General Structure of SR Beamline Examples: - Material Science and Power Diffraction BL (ALBA) - Pression Structure Imagerie par Contraste à Haute Énergie (Psiché, Soleil) - ID27 High Pressure BL, ID09A - White Beam Beamline, High Pressure Station (ESRF) 9

10 XRD at high pressures Synchrotron radiation - Bragg s law: Two different experimental approaches Fixed q, variable l(e) Fixed l (E), variable q Energy dispersive XRD (EDXRD) Angle dispersive XRD (ADXRD) 10

11 Outline EDXRD Outline: - X ray diffraction at high pressures. - Special needs. - Synchrotron radiation. - EDXRD - ADXRD - Single crystal XRD - Examples. 11

12 XRD at high pressures EDXRD Energy dispersive x-ray diffraction (EDXRD) Amplificator Incident white beam (Wiggler) 2q Diffraction parallelogram Intensidad Multicanal analyzer Energía (kev) 2d sinq l hc E Main disadvantage: The quantitative analysis of diffracted intensities is not easy. Fixed q: d hkl ( Å) E hkl ( kev )sinq Usually only cell parameters are obtained! 12

13 XRD at high pressures EDXRD EDXRD set-up in ID30 (now ID27), ESRF 2q 1. Entrance slit 2. HP cell (PE) 3. Cell support (translation and/or rotation) 4. Diffraction slits 5. Ge detector (next to a liquid N 2 dewar) 13

14 XRD at high pressures EDXRD ZnSe x Te 1-x alloys J. Pellicer-Porres et al., PRB 65, (2002) PRB 71, (2005) 14

15 Outline ADXRD Outline: - X ray diffraction at high pressures. - Special needs. - Synchrotron radiation. - EDXRD - ADXRD - Single crystal XRD - Examples. 15

16 XRD at high pressures Intensity ADXRD Angle dispersive x-ray diffraction (ADXRD) White beam Monochromatic beam Sample 2q (undulator or wiggler) Monocromator Colimador 2D detector (image plate, CCD) Integration Digitalization 2q 2d sinq l l l 0 fijo d hkl Å) l 2sinq 0 ( hkl 16

17 XRD at high pressures ADXRD Example: Stanford Synchrotron Radiation Laboratory (SSRL) 17

18 XRD at high pressures ADXRD Berlinite (AlPO 4 ) - Rietveld refinements at very high pressures (Mbar). P=14 GPa P=97 GPa J. Pellicer-Porres et al., Nature Materials 6, (2007) 18

19 Outline Single crystal XRD Outline: - X ray diffraction at high pressures. - Special needs. - Synchrotron radiation. - EDXRD - ADXRD - Single crystal XRD - Examples. 19

20 XRD at high pressures Single crystal XRD Single crystal diffraction k k = K The Laue condition is not so easy to fulfill! - The single crystal analysis is complicated under HP: - Absorption from the sample environment. - Limited access to the reciprocal space. - Reflections from the sample environment. - Long experiments. - No global image. - Reconstructive phase transitions.

21 XRD at high pressures Advantages in single crystal XRD (1/3) - There is no reflection overlapping (in particular for d<1.5 Å) - There are no grain contacts - Equations of state can be determined with high precision. GaS equation of state - Layered compound. - 70x10x10 μm 3 sample - l=0.37 Å - Image plate - ~40 reflections Single crystal XRD J. Pellicer-Porres et al., Phys. Stat. Sol. (b) 244, (2007) 21

22 XRD at high pressures Advantages in single crystal XRD (2/3) - Systematic absences /spatial group. - Access to reciprocal vectors (opposed to distances). - Accurate determination of intensities and structural factors. - Structural models. Jahn-Teller distortions in CuWO4 - Boehler-Almax DAC x 70 x 20 μm 3 sample - l=0.45 Å - NaI point detector. Single crystal XRD P1 P 2/ c J. Ruiz-Fuertes et al., Chem. Mater. 23, (2011) 22

23 XRD at high pressures 10 GPa Single crystal XRD Advantages in single crystal XRD (3/3) - It is possible to study light elements (small atomic form factors). Hydrogen equation of state 14 GPa 119 GPa - Thanks to the EDXRD configuration the Loubeyre et al., contribution from the diamonds to the background Nature 383, 702 (1996) (Compton scattering) is minimized 23

24 Outline Examples Outline: - X ray diffraction at high pressures. - Examples. - Equation of state. - Phase transitions. Hysteresis. - Synthesis. 24

25 Examples Equation of state Hydrogen at high pressures -Wigner&Huntington (1935): Transformation from a molecular solid to a monoatomic metal at 25 GPa. - N. W. Ashcroft (1968): Metallic hydrogen would be a high temperature superconductor. Enormous difficulties, from both the experimental and theoretical points of view! 25

26 Examples Equation of state Hydrogen equation of state 10 GPa 14 GPa 119 GPa 26

27 Examples Equation of state GaS equation of state - Layered compound. - 70x10x10 μm 3 sample - l=0.37 Å - Image plate - ~40 reflections J. Pellicer-Porres et al., Phys. Stat. Sol. (b) 244, (2007) 27

28 Outline Phase transitions. Hysteresis. Outline: - X ray diffraction at high pressures. - Examples. - Equation of state. - Phase transitions. Hysteresis. - Synthesis. 28

29 Examples Hysteresis and potential barriers G P T V 0 Phase transitions. Hysteresis. ZnO M. Flórez and J. M. Recio et al., in Introduction to High Pressure Science and Technology F. Decremps et al., EPL 51, (2000) Nano ZnO J. Pellicer-Porres et al., APL 81, (2002)

30 Examples Phase transitions. Hysteresis. Overcoming potential barriers: berlinite -Quartz homeotype AlPO 4 - Berlinites: ABO 4 - Is there a crystal-amorphous phase transition? Science 249, 647 (1990) Science 255, 1559 (1992) Spirals of alternate tetrahedra in berlinite structure PRL 71, 3143 (1993). 30

31 Examples Phase transitions. Hysteresis. Overcoming potential barriers: berlinite - Example: Cmcm phase in AlPO 4 Laser heating J. Pellicer-Porres et al., Nat. Mat. 6, (2007) a (Å) b (Å) c (Å) S. M. Sharma et al S.M. Sharma et al, PRB 62, 8824 (2000). J. Pellicer-Porres et al

32 Examples Phase transitions. Hysteresis. Hysteresis and potential barriers: path selection - Phase transitions in ZnTe 0.2 Se 0.8 : - Upstroke: ZB NaCl - Downstroke: NaCl Cin ZB 11 GPa 10.5 GPa 10.4 GPa 10.3 GPa 10.2 GPa 32

33 Examples Semiconductores III-V y II-VI ZnSe x Te 1-x alloys V. Ozolins and A. Zunger, PRL 82, 767 (1999) J. Pellicer-Porres et al., PRB 65, (2002) PRB 71, (2005) 33

34 Outline Synthesis Outline: - X ray diffraction at high pressures. - Examples. - Equation of state. - Phase transitions. Hysteresis. - Synthesis. 34

35 Examples Diamond synthesis H. Tracy Hall 1953 First diamond synthesis 1954/12/16 F.P. Bundy et al. Nature 176, 51 (1955) Synthesis Hall, Rev. Sci. Instrum. 31, 125 (1960) 35

36 Examples Synthesis In situ studies Example: Photon Factory, Ni Utsumi et al, J.Phys.: Condens. Mat. 16, S1017(2004) 36

37 Examples Synthesis Industrial diamond synthesis ton press Belt -type P max =6 GPa 1 liter Kobelco: Kobe Steel Group products/ip/product/press_01.html 37

38 Additional information: CRC, in press Do not forget x-ray absorption! Thank you for your attention! 38