X-ray powder diffractometer X-ray powder diffractometer

X-ray powder diffractometer radiation counter radiation counter

X-ray powder diffractometer

Powder diffractometer (see Jenkins & Snyder, chap. 7)

Bragg-Brentano geometry

X-ray powder diffractometer

To maintain the focusing geometry, when counter is rotated at rate of 2  /min, specimen is also rotated at rate of  /min  /min  /min

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here, is main rotation axis - asymmetric broadening toward low 2  - negative 2  error up to 90° - positive 2  error beyond 90° Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here, is main rotation axis - asymmetric broadening toward low 2  - negative 2  error up to 90° - positive 2  error beyond 90°

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here, is main rotation axis Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here, is main rotation axis

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here is main rotation axis each section of Soller slit produces its own Debye ring from a specific region in the specimen divergence angle typically ±2.5° Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here is main rotation axis each section of Soller slit produces its own Debye ring from a specific region in the specimen divergence angle typically ±2.5°

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here is main rotation axis each section of Soller slit produces its own Debye ring from a specific region in the specimen divergence angle typically ±2.5° Bragg-Brentano instrument - errors (see Klug & Alexander) Axial divergence - axis, here is main rotation axis each section of Soller slit produces its own Debye ring from a specific region in the specimen divergence angle typically ±2.5°

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Flat specimen peak shifts to lower 2  & asymmetric broadening depends on beam divergence & 2 , plus specimen shape Bragg-Brentano instrument - errors (see Klug & Alexander) Flat specimen peak shifts to lower 2  & asymmetric broadening depends on beam divergence & 2 , plus specimen shape

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Specimen transparency Bragg-Brentano instrument - errors (see Klug & Alexander) Specimen transparency

Powder diffractometer Bragg-Brentano instrument - errors (see Klug & Alexander) Specimen displacement Usually largest error in expt'l data Neg. peak shift - ~0.01° 2  /15  displacement Asymmetric broadening toward lower 2  Bragg-Brentano instrument - errors (see Klug & Alexander) Specimen displacement Usually largest error in expt'l data Neg. peak shift - ~0.01° 2  /15  displacement Asymmetric broadening toward lower 2 

Powder diffractometer Bragg-Brentano instrument Divergence slit choice Bragg-Brentano instrument Divergence slit choice

Powder diffractometer Bragg-Brentano instrument Divergence slit choice Or, theta-compensating slit - divergence slit opens as theta increases Bragg-Brentano instrument Divergence slit choice Or, theta-compensating slit - divergence slit opens as theta increases

Powder diffractometer Bragg-Brentano instrument Receiving slit choice Bragg-Brentano instrument Receiving slit choice

Powder diffractometer Bragg-Brentano instrument Receiving slit choice lowers intensity - little improvement in resolution poor resolution - little improvement in intensity Bragg-Brentano instrument Receiving slit choice lowers intensity - little improvement in resolution poor resolution - little improvement in intensity

Powder diffractometer Bragg-Brentano instrument Receiving slit choice correct slit size ~0.15° Bragg-Brentano instrument Receiving slit choice correct slit size ~0.15°

Powder diffractometer Alignment steps

Powder diffractometer Alignment steps Align to focal spot Set take-off angle Alignment steps Align to focal spot Set take-off angle

Powder diffractometer Alignment steps Align to focal spot Set take-off angle Zero alignment 2:1 alignment Alignment steps Align to focal spot Set take-off angle Zero alignment 2:1 alignment

Powder diffractometer Alignment steps Align to focal spot Set take-off angle Zero alignment 2:1 alignment Alignment steps Align to focal spot Set take-off angle Zero alignment 2:1 alignment

Powder diffractometer Alignment steps Align to focal spot Set take-off angle Zero alignment 2:1 alignment Alignment steps Align to focal spot Set take-off angle Zero alignment 2:1 alignment

Powder diffractometer Alignment checks Run calibration pattern - use suitable standard NIST 640c (Si) Alignment checks Run calibration pattern - use suitable standard NIST 640c (Si)

Powder diffractometer Alignment checks Run calibration pattern - use suitable standard Alignment checks Run calibration pattern - use suitable standard

Powder diffractometer Alignment checks Run calibration pattern - use suitable standard Watch for: Intensity loss Angle shifts Resolution loss Alignment checks Run calibration pattern - use suitable standard Watch for: Intensity loss Angle shifts Resolution loss

Powder diffractometer Alignment checks

Powder diffractometer Alignment check "Five fingers of quartz" Alignment check "Five fingers of quartz"

Powder diffractometer Alignment check "Five fingers of quartz" Measure: position & intensity of (203)  1 H 1 /H 2 Alignment check "Five fingers of quartz" Measure: position & intensity of (203)  1 H 1 /H 2

Powder diffractometer Alignment checks Run calibration pattern - use suitable standard NIST 1976 (Al 2 O 3 ) Alignment checks Run calibration pattern - use suitable standard NIST 1976 (Al 2 O 3 )

Powder diffractometer Alignment checks Run calibration pattern - use suitable standard Alignment checks Run calibration pattern - use suitable standard

Powder diffractometer Alignment checks Run calibration pattern - use suitable standard Alignment checks Run calibration pattern - use suitable standard