ACII-Part II: Structure of solids; Structure-properties relationship

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1 ACII-Part II: Structure of solids; Structure-properties relationship Dr. Liliana Viciu ACII: Prof. Reinhard Nesper and Dr. Liliana Viciu 1

2 Liliana Viciu B. Sc. and M.Sc. at University of Bucharest, Romania Ph.D. at University of New Orleans, USA Contact info: Office HCI H101 Tel:

3 TOPICS 1. Properties we see in solids 2. Basic crystallography 3. Introduction to crystals symmetry 4. Diffraction on crystals 5. Important crystal structures in solid state chemistry and properties associated with them 3

4 Bibliography 1. Anthony R. West: Solid State Chemistry and its Applications 2. Ulrich Müller: Inorganic Structural Chemistry (online book through ETH library) 3. Martin Bürger: An introduction to fundamental geometric features of crystals 4. Werner Massa: Crystal Structure Determination Slides on: username: aach password: jsenpw 4

5 The type of properties we see in solids; Syllabus Solids classification based on bonds and atomic arrangement Basic Crystallography (Bravais Lattice; Crystal lattice; crystal structure; counting atoms; crystal density; packing density; characteristic of cubic systems); Symmetry concepts: symmetry operations; symmetry in 2D; plane groups; symmetry in 3D; space groups and some examples of symmetry applications Lattice directions; lattice planes Miller indices; Diffraction on lattice planes; constructive and destructive interferences; systematic absences; patterns indexing Packing of atoms: properties of solids explained by packing; voids in close packed structures; structure build by space filling polyhedral; Important structure types: close packed structures and non-close packed structures 5

6 Solid Materials in our daily life 6

7 Materials development in early civilizations Stone Age (2.5 million BC) Bronze Age (3500 BC) Iron Age (1000BC) 7

8 Materials Types metals (metals and alloys) ceramics (oxides, nitrides, carbides, glasses, concrete) polymers (plastics, rubbers) composites (fibers) 8

9 Advanced Materials semiconductors for sophisticated electronic devices (i.e. energy conversion) energy storage (batteries, ultracapacitors) thermoelectric materials magnetic information storage optical fibers and piezoelectric materials as sensors 9

10 Solid state chemistry Development of materials: synthesis, structure, and properties Understand the relation between structure and properties 10

11 11

12 1. Nontoxic, unreactive with the beverage 2. Barrier to CO 2 passage 3. Mechanical strength 4. If optically transparent retain its optical clarity 5. Ease of fabrication 6. Low cost 12

13 Identifying Properties The response of a material to an external stimulus Type of external stimuli: 1.Deformation 2.Electrical field 3.Temperature 4.Magnetic field 5.Light 13

14 1. Deformation Mechanical properties Deformation = the ability to change the shape when load/forces are applied elastic deformation (reversible) stiffness plastic deformation (irreversible) strength, hardness, malleability and ductility

15 Malleability and ductility of some metals is understood by their close packed structures: cubic close packed (ccp or fcc) > hexagonal close packed, hcp, structured > body centered cubic (bcc) * * Nb is an exception! 15

16 2. Electric field Conduction properties Conduction = ability to conduct charge through a solid 2.1. Ionic Conductors 2.2. Electronic Conductors Insulators Semiconductors Metals Superconductors 16

2.1. Ionic Conductors Charge migration or charge diffusion increases with temperature conduction through cations (NaCl type solids) ex: NaCl, MgO, - Li 3 N, AgI conduction through anions(caf 2

17 2.1. Ionic Conductors Charge migration or charge diffusion increases with temperature conduction through cations (NaCl type solids) ex: NaCl, MgO, - Li 3 N, AgI conduction through anions(caf 2 type solids) ex: ZrO 2 stabilized with CaO or Y 2 O 3 Batteries = energy conversion + energy storage Solid oxide fuel cells = energy conversion 17

18 2.2. Electronic Conductors The flow of electrons/holes throughout a solid conductivi ty, ne e = charge (constant; independent of temp.) = mobility of carriers (decreases slightly with increases of temp.) n = nr of charge carriers Insulators Semiconductors Metals Solid Ag Cu Al Graphite Si Ge GaAs Diamond Electrical Conductivity (Sm -1 ) 6.1x x x x x x

19 Band gap in solids Electronic conduction explained by energy band theory Metals no band gap Eg 3 ev semiconductor (i.e., Eg Si = 1.1eV) Eg > 3 ev insulator (ex Eg diamond = 5.4eV) Solid Band Gap Eg (ev) Structure type Diamond Si Ge InSb GaAs Diamond Diamond Diamond Zinc blende Zinc blende 19

20 Insulators: Dielectrics Resist to the flow of electric charge Have large band gaps (Eg>3eV) (capacitors) Dielectrics (change in polarization with an applied electric field) surface charge due to the internal dipols formation = polarization, P R. Tilley: Understanding solids, The science of Materials, J.Wiley &Sons,2006 In some dielectrics change in polarization arises from mechanical stress piezoelectric In some piezoelectrics change in polarization arises from change in temperature pyroelectric In some pyroelectrics the polarization is easily switched in an electric field ferroelectric 20

21 Structures with no inversion center could show piezoelectricity ex: structures with Td groups like ZnS-zinc blende (sphalerite) and ZnS-wurtzite type structures) Perovskite structures with d 0 transition metals show pyroelectricity and even ferroelectricity 21

22 Examples of Dielectrics Piezoelectrics: quartz resonators, power generating floors, lighters, etc Pyroelectrics: temperature sensors, power generation Ferroelectric: capacitors, ferroelectric RAMs a b c a. Ferroelectric b. Anti-ferroelectric c. Ferroelectric polarization 22

23 Semiconductors Conductivity increases as temperature increases the carrier concentration, n, increases as temp goes up due to excitations across the band gap, Eg) Conduction band ~ e Eg / kt Eg (band gap) Conductivity of a semiconductor will increase exponentially (up to a point) with an increase in temperature! Valence band Mobility,, increases with molecular weight and decrease with electronegativity difference (polarization effect of mobile electrons or holes on the surrounding atoms) 23

24 Semiconductors have often diamond or ZnS blende (sphalerite) structure. Due to the covalent character of its bonding interaction (the lattice is always composed of those elements with the smallest difference in electronegativity). 4/10/2013 L.Viciu ACII Imprtant structure types 24

25 Examples of semiconductors at work the center of solid-state electronics: Si, Ge, Sn, III-V compounds (GaAs, InSb ) and II-VI compounds ( CdTe) Solar cells (photovoltaics) 25

26 Metals Conductivity decreases with increasing temperature the number of charge carriers, n, do not vary with temperature (higher energy levels are still in the valence band) Conduction band ne No Eg, (band gap) Valence band Mobility,, decreases with increasing temperature (the lattice vibrations will scatter the electrons collisions with the crystal lattice) 26

27 Examples of metallic conductors Solid Ag Cu Al Graphite Electrical Conductivity (Sm -1 ) 6.1x x x x10 4 NiAs - type compounds (not layered structure) and often in layered structures (MoS 2, graphite) where orbital overlap is enhanced on certain directions (z direction vs xy plane) show metallic conduction 27

type I: mobile electrons in pairs Cooper pairs SC type II: High Tc

28 Superconductors In the superconductivity state no electrical resistance - the current will flow forever without diminishing SC- type I: mobile electrons in pairs Cooper pairs SC type II: High Tc superconductors cuprates, MgB 2, Fe-based superconductors mostly layered structures 28

29 Superconductors at work MRI NMR B MRI = gauss B Earth = gauss Maglev 29

3. Temperature Thermal behavior Thermal conduction = attributed to the mobile electrons (in metals) and phonons in ceramic materials Ex: diamond, BN, SiC Thermal expansion and

30 3. Temperature Thermal behavior Thermal conduction = attributed to the mobile electrons (in metals) and phonons in ceramic materials Ex: diamond, BN, SiC Thermal expansion and contraction Ex: memory shape alloys (CuZnAlNi, CuAlNi, NiTi=nitinol) used in medicine and aerospace Thermoelectric effects: combines thermal conduction and electronic conduction 30

4. Magnetic field Magnetic Properties Each electron has a magnetic moment due to the existence of a magnetic dipole (electron spin) (a) diamagnetic materials (repealed by a

31 4. Magnetic field Magnetic Properties Each electron has a magnetic moment due to the existence of a magnetic dipole (electron spin) (a) diamagnetic materials (repealed by a magnetic field) (b) paramagnetic materials (attracted by a magnetic field) Spin interaction in paramagnetic materials ferromagnetic(i) and antiferromagnetic (ii) materials (i) (ii) 31

32 Perovskite materials with d n transition metals Spinel structure with magnetic ions such as Fe, Co, Ni, etc 32

Applications of magnetic materials Information storage, transformer cores, permanent magnets Ex: Fe2O3, Co, Ni- based materials, yttrium iron garnet (YIG=Y 3 Fe 5 O 12 )

33 Applications of magnetic materials Information storage, transformer cores, permanent magnets Ex: Fe2O3, Co, Ni- based materials, yttrium iron garnet (YIG=Y 3 Fe 5 O 12 ) Spintronics devices: MRAM, sensors, spin transistor, spin memory Electron flux through a ferromagnetic layer Ex: Mn doped II-VI and III-V semiconductors; GaAs; Co doped TiO 2 33

$(selective absorption) Refraction and dispersion$ (apparent bending and separation of white light)

direction return to the medium) Scattering

$stone Diffraction (apparent bending of waves around$

34 5. Light = Optical properties Color and appearance (selective absorption) Refraction and dispersion (apparent bending and separation of white light) Ex: diamond dispersion Reflection (change in direction return to the medium) Scattering (spreading from straight trajectory) Ex: blue moon stone Diffraction (apparent bending of waves around small obstacles and the spreading out of waves past small openings) 34

35 Composition Structure Performance Properties Design and construction 35

36 Solid Materials Package of Properties Properties f(composition) Choice of composition + Crystal Structure Properties of Materials 36

graphite Composition alone can t give the properties of a

37 Solid properties = f(composition) Solid properties = f(atomic arrangement) Ex: diamond vs. graphite Composition alone can t give the properties of a material, they are dependent on the atomic arrangement. pictures from wikipedia 37

38 Solid State Chemistry Electronic structure of the elements holds the key to the understanding of the long range atomic order in solids; Electronic structure of the atomic constituents and symmetry arguments are the criteria for the material selection process 38

39 Interatomic bonding 3D- atomic arrangement Crystal structure Symmetry arguments 39

40 Interatomic bonding 3D- atomic arrangement Crystal structure Symmetry arguments Material selection process 40

41 1. What atoms are involved and their electronic configuration? 2. What types of chemical bonds are formed? 3. How are the atoms arranged in the crystal structure? 4. What is the symmetry of the crystal? 5. Do these arrangements promote certain mechanisms for electronic or atomic motions? 6. How do these mechanisms give rise to the observed properties? 41

SOLID STATE PHYSICS. Second Edition. John Wiley & Sons. J. R. Hook H. E. Hall. Department of Physics, University of Manchester

SOLID STATE PHYSICS. Second Edition. John Wiley & Sons. J. R. Hook H. E. Hall. Department of Physics, University of Manchester SOLID STATE PHYSICS Second Edition J. R. Hook H. E. Hall Department of Physics, University of Manchester John Wiley & Sons CHICHESTER NEW YORK BRISBANE TORONTO SINGAPORE Contents Flow diagram Inside front