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Material Characterization Slide 1
Analytics of Materials
Contents
1. Methods of Material Characterization
2. Physical Basis
3. Experimental Setup
4. Methods of Optical Material Characterization
4.1 Absorption Spectroscopy
4.2 Luminescence Spectroscopy
4.3 Reflection Spectroscopy (Remission spectroscopy)
Material Characterization Slide 2
Literature
- B. Schröder, J. Rudolph Physikalische Methoden in der Chemie, VCH, 1985
- H. Naumer, W. Heller Untersuchungsmethoden in der Chemie, Georg Thieme Verlag, 1990
- E.A.V. Ebsworth, D.R.H. Ranklin, S. Cradock, Structural Methods in Inorganic Chemistry, Blackwell Scient. Publications, 1991
- W. Schmidt Optische Spektroskopie, VCH, 1993
- M. Hesse, H. Meier, B. Zeeh Spektroskopische Methoden in der organischen Chemie, VCH, 2005
- J.B. Lambert, S. Gronert, H.F. Shurvell, D.A. Lightner Spektroskopie - Strukturaufklärung in der organischen Chemie, Pearson, 2012
Material Characterization Slide 4
1. Methods of Material Characterization
- Chemical composition Elementary analysis Main and secondary components X-ray fluorescence analysis Main and secondary components Atomic absorption spectroscopy Trace elements, dopants Powder diffractometry Phase composition Infrared spectroscopy (IR) Detection of functional groups Raman spectroscopy Detection of functional groups Differential thermal analysis Phase transformations, crystallization water
- Morphological characterization (micro and nanostructure) (Dynamic) Light scattering Particle size distribution Optical microscopy Particle morphology Scanning electron microscopy Particle size distribution, surface structure Transmission electron microsc. Crystallinity, texture BET-isotherm Specific surface area
Material Characterization Slide 5
1. Methods of Material Characterization
- Structural characterization Powder diffractometry Phase identification, crystal system, space group X-ray structure analysis Space group, atomic coordinates X-ray absorption spectroscopy Chemical environment of heavy atoms NMR spectroscopy Molecular structure Infrared spectroscopy (IR) Molecule identification Arrangement of functional groups Raman spectroscopy Arrangement of functional groups Resonance-Raman spectroscopy Arrangement of functional groups
- Surface characterization Electrosonic Amplitude (ESA) Surface charge, isoelectric point Mass spectroscopy (SIMS) Adsorption of organic molecules at surfaces X-ray photoelectron Surface composition spectroscopy (ESCA/XPS)
Material Characterization Slide 7
2. Physical Basis
2.1 Classification of Optical Spectroscopy 2.2 The Electromagnetic Spectrum 2.3 Time Scale of Physical Processes 2.4 Interaction of Light and Matter Types of Electromagnetic Interaction Electronic States in Atoms Electronic States in Solids Reflection Absorption Refraction Luminescence 2.5 Radiometric Quantities 2.6 Photometric Quantities 2.7 Photosynthetically Active Radiation
Material Characterization Slide 8
2.1 Classification of Optical Spectroscopy
Absorption Reflection Scattering (Raman, Rayleigh) Luminescence Atom- Absorption (AAS) Molecule- Absorption (UV/Vis/NIR) Optical spectroscopy Excitation Emission Luminescence spectroscopy Energy dependent Temperature resolved Decay curves, persistent luminescence, flicker Time resolved Defect or thermo luminescence Thermal quenching Excitation spectrum
Material Characterization Slide 10
2.2 The Electromagnetic Spectrum
Energy of photons E = h h = 6. . 10
- 34 Js E = hc/l c = 2. . 10 8 m/s E = NAhc/l = 119226 /l kJmol
- 1 The energy is thus proportional to the reciprocal length, to so-called wavenumber with = 1/l E = h . c . = 1. . 10
[eV] = 1240/l [eV] or 1 eV ~ 8065 cm
- 1 Parameters proportional to energy
- Frequency [Hz]
- Wavenumber [cm
- 1 ] 10 -^16 m 3. 1024 Hz 1. 1014 cm-^1 12.4 GeV 10 -^14 m 3. 1022 Hz 1. 1012 cm-^1 124 MeV 10 -^10 m 3. 1018 Hz 1. 108 cm-^1 12.4 keV 10 -^12 m (1 pm) 3. 1020 Hz 1. 1010 cm-^1 1.24 MeV 10 -^8 m 3. 1016 Hz 1. 106 cm-^1 124 eV 10 -^6 m (1 μm) 300 THz 1. 104 cm-^1 1.24 eV 10 -^4 m 3 THz 100 cm-^1 12.4 meV 10 -^2 m 30 GHz 1 cm-^1 0.124 meV 100 m (1 m) 300 MHz 0.01 cm-^1 1.24 μeV 102 m 3 MHz 1. 10 -^4 cm-^1 12.4 neV Wavelength l Frequency Wavenumber Energy E
~
Material Characterization Slide 11
2.3 Time Scale of Physical Processes
Chem. reactions < molecular rotation < molecular vibration < electron motion Franck-Condon Principle Since the nuclei are much heavier than the electrons, the electronic transition takes place so rapidly that the nuclei have no time to react (Born-Oppenheimer approximation) Separation of electron- and nucleus motion The electron continually transitions from one stationary state to the other.
Material Characterization Slide 13
2.4 Interaction of Light and Matter
Electronic states in multi electron atoms Atom Electron configuration Ground state First excited state Na 0 1s 2 2s 2 2p 6 3s 1 2 S1/ 2 P3/2, 2 P1/
(yellow Na-double line at 589.0 and 589.6 nm Spectrometer resolution test)
Cr 3+ 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 3 4 F 4 P Ce 3+ [Xe]4f 1 2 F5/2, 2 F7/ 2 D Eu 3+ [Xe]4f 6 7 F 0 5 D 0 Gd 3+ [Xe]4f 7 8 S7/ 6 PJ Selection rules for electric dipole transitions
- Spin selection rule S = 0
- Orbital angular momentum l = +/-1, ml = 0, +/- 1
- Laporte selection rule g → u, u → g, but not g → g, u → u With Russell-Saunders (LS) coupling: L, J = 0, +/-1, but not J = 0 → J = 0 S = s L = |l| J = L+S, L+S-1, … |L - S| Russell-Saunders- Terms (energy levels) 2S+1L J
Material Characterization Slide 14
2.4 Interaction of Light and Matter
Electronic transitions in multi electron atoms Typ [lmol
- 1 cm - 1 ] Example Electron from to___ s-p transitions l = 1 10 3
- 10 4 Na 0 3s → 3p d-d transitions l = 0 < 10 2 Cr 3+ 3d (t 2 ) → 3d (e) f-d transitions l = 1 10 4 - 10 5 Ce 3+ 4f → 5d f-f transitions l = 0 < 10 2 Eu 3+ 4f → 4f Gd 3+ 4f → 4f Tb 3+ 4f → 4f Forbidden due to large change in orbital angular momentum: s-d l = 2 p-f l = 2 s-f l = 3 parity allowed
- these transitions are strongly forbidden!
Material Characterization Slide 16
2.4 Interaction of Light and Matter
Electronic states in solids (metals, semiconductors, ceramics) Direct semiconductors: Indirect semiconductors: Absorption or emission of a photon Phonon assisted absorption or emission of a photon → strong: GaAs, GaN → weak: Si, Ge
Material Characterization Slide 17
2.4 Interaction of Light and Matter
Absorption by
- Excitation band: valence band-conduction band
- Defects (color centers) “blue ice”
- Transitions between energy levels of dopants (Tb 3+ ) or impurities Acceptor levels Donor levels Valence band Conduction band Band gap Eg YBO 3 Vaterit Band gap Eg = 6.5 eV Electronic states in solids Tb3+ levels
Material Characterization Slide 19
2.4 Interaction of Light and Matter
Reflection
- Specular reflection (regular) Reflection from a polished (smooth) surface in one direction (reflecting surface) Example: metal, mirror, calm water surface
- Diffuse reflection (irregular) Reflection from a non-polished surface in all directions of the half-space (matte surface) Example: paper, powder, white wall Angular distribution of a Lambert radiator's
1
2
2
1 S 0 cos Bcos
B
Material Characterization Slide 20
2.4 Interaction of Light and Matter
Absorption Medium = gas, solution, crystal, transparent ceramics Lambert-Beer-Bouguer-law I = I 0 exp(-c*d) ln(I/I 0 ) = - cd Absorption: A = cd = Absorption constant [cm
- 1 ] Fate of the absorbed energy Physical effect Application areas
- Vibrations (phonons) Heat bolometer
- Charge storage Color centers detectors, imaging plate
- Luminescence Light emission phosphors, laser gain media
- Charge separation Current solar cells x
I
I 0
IT
0 d
I 0 IT
Sample
