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XRDRaman spectroscopy

Conclusions

XRD and Raman spectroscopyF8900 Študentský seminár

Peter Zelinapetko@physics.muni.cz

Department of Physical ElectronicsFaculty of ScienceMasaryk University

May 4th, 2011

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

Conclusions

Outline

1 XRDIntroductionPrinciple

2 Raman spectroscopyTheoryPrinciple

3 Conclusions

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

ConclusionsIntroductionPrinciple

What is XRD?

X-Ray Diffraction = X-rays diffracted on lattice of the matterconstructive interference (Braggs condition):

2d sin θ = nλ2 a√

h2+k2+l2 sin θ = λ

When do I use XRD?qualitative and quantitative analysis of crystalline sampledistinguish between mixture and compoundsize of particles (powder XRD, size < 100 nm)

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

ConclusionsIntroductionPrinciple

How mathematics works...

F (~Q) =∑

sfs(Q)

structure factor︷ ︸︸ ︷exp(−i ~Q ·~rs) (1)

~rs direct lattice vector, ~Q reciprocal lattice vector ⇒ condition forMiller indeces h, k, l ⇒ angle of incidence θ

α-Fe Fe3O4hkl 2θ[◦] hkl 2θ[◦]

110 52 111 21200 77 220 35211 100 311 41220 124 400 50310 161 511 67

440 74

LP#14a - α-Fe/Fe3O4: 44:56; 10 nm, 4 nm

Scherer formula:

τ =Kλ

β cos θ

β = FWHMK - shape factor

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

ConclusionsIntroductionPrinciple

...and physics

source of X-rays: synchrotron, bremsstrahlung(Mo, Cu, Co, Fe, Cr)λ ≈ 0.06 nm (Mo) – 0.23 nm (Cr)

detector: CCD, photopaper

MoO3 nanowires, www.nanotul.com

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

ConclusionsTheoryPrinciple

Raman spectroscopy - Basic theory

inelastic scattering of monochromatic lightexcitations to virtual energy statessource: laser (λ0) - near UV – near IR

∆ω = (1λ0− 1λ

) (2)

When do I need Ramanspectroscopy?

info about spectra of molecules,chemical bondssolids, liquids, samples in water,glassNON-destructive, quick,no preparations needed

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

ConclusionsTheoryPrinciple

Principle

light irradiates the samplescattered light is detectedwavelengths λ ≈ λ0 are filtered

Applicationsdrugs, explosives detectionlow energy phononscomplement to IR spectroscopy

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

Conclusions

To sum upWe use...

XRD if...the sample is (poly)crystalline!qualitative, quantitative analysisnanopowder - size of particles

Raman spectroscopy if...info about rotational, vibrationalspectra, chemical bonds,phonon and magnon excitationscomplement to IR spectroscopy

Method is useless if...

the sample is NOT crystallinevery small objects (≈ λ)similar lattice parameters

laser changes structure of thesample, heats itthe sample is metal or alloy

Thank you for your attention!

Peter Zelina XRD and Raman spectroscopy

XRDRaman spectroscopy

Conclusions

To sum upWe use...

XRD if...the sample is (poly)crystalline!qualitative, quantitative analysisnanopowder - size of particles

Raman spectroscopy if...info about rotational, vibrationalspectra, chemical bonds,phonon and magnon excitationscomplement to IR spectroscopy

Method is useless if...

the sample is NOT crystallinevery small objects (≈ λ)similar lattice parameters

laser changes structure of thesample, heats itthe sample is metal or alloy

Thank you for your attention!

Peter Zelina XRD and Raman spectroscopy