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Lecture 2.1 Crystalline Solids. Poly-crystalline solids - Grains Mono-crystalline solids- Whiskers, Wafers.

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Presentation on theme: "Lecture 2.1 Crystalline Solids. Poly-crystalline solids - Grains Mono-crystalline solids- Whiskers, Wafers."— Presentation transcript:

1 Lecture 2.1 Crystalline Solids

2 Poly-crystalline solids - Grains Mono-crystalline solids- Whiskers, Wafers

3 Crystal Lattices

4 Crystal Systems =>14 Bravais Lattices

5 Bravais lattice (abc) Lattice is constructed of repeated unit cells Lattice Point - 1/3a,1/2b,1/4c Crystallographic Direction (vector from 0,0,0 to xyz) which is defined by –[uvw] smallest set of integers having the same ratio as xyz –bar over number = minus number

6 Close Packed Structures Cubic, BCC, FCC, HCC are the focus of this course Determining distances and volume fractions in Cubic Structures

7 Miller indices for a plane (hkl) Family of Miller Planes {hkl}

8 EXAMPLE- Miller Index intercepts on a,b&c axes=3,1&2, respectively reciprocals = 1/3,1/1&1/2, respectively smallest set of integers with same common ratio = 2,6&3 Miller indexes of Plane, (hkl)=(263) also called “reciprocal space plane”

9 Family of Planes {110}

10 Measuring Structure with X-rays Generate X-ray radiation X-ray Diffraction (  =90) –a o = cubic lattice parameter

11 X-Ray Generation Electron Scattering –Broad Band X-rays Electron Kickout –K,L,M shell electron –Replace with higher electron –Transition gives X- rays one wave length K ,K , L , L  KK KK

12 X-ray Generation Energy Level Diagrams 1 K eV eV eV L eV KK KK LL LL

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14 X-ray Camera-1 Single Crystal Camera –Broad Band X-rays –all in source –only Bragg (diffracting) wavelengths reflect

15 SiGe Crystal

16 X-ray Camera-2 (film strip) X-rays of Single All (hkl) planes are exposed at all angles at all times Diffraction of Bragg planes

17 Electron Diffraction Electrons of different energy Transmission through sample CCD detector Focused Electrons Thinned Sample CCD Detector

18 Seeing Crystal Structure with and Atomic Force Microscope Electron Microscope Atomic Force Microscope Scanning Tunneling Microscope

19 Diffracting Planes

20 Changing Crystal Structure – Allotropic Phase Change HCP->FCC->BCC->SC Ca(fcc) --(447ºC)-> Ca(bcc) Co(hcp) --(427ºC)--> Co(fcc) Fe(bcc) --(912ºC)-->Fe(fcc) --(1394ºC)-->Fe(hcp) Na(bcc) --(-233ºC)--> Na(hcp) Ti(hcp) --(883ºC)-->Ti(bcc) Zr(hcp) --(872ºC)--> Zr(bcc) Decreasing density with increasing temperature!

21 Defects in Crystal Structure Vacancy, Interstitial, Impurity Schottky Defect Frenkel Defect Dislocations – edge dislocation, line, screw Grain Boundary

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27 Effect of Structure on Mechanical Properties Elasticity Plastic Deformation


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