INORGANIC SOLIDS. Pigment. Garnet. Cement Visible rays : nm. Gold. Marble. Human Eyes Resolution = 0.07 mm

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1 Garnet INORGANIC SOLIDS Pigment Quartz Gold Cement Visible rays : nm Human Eyes Resolution = 0.07 mm Marble CD IC

2 SEM 100nm Inside a solid : how the grains look 1 micron to 10 microns : Normal grains in solids 1 micron = 1/1000 mm

3 Ordered arrangement of atoms : crystalline solids ATOMIC LIMIT Diamond 1 atom( dia) : nm 1 small crystal : ~10 21 atoms 3-Dimensional X-rays : nm Dislocation

4 Solids AKG CRYSTALLINE (Long range order) NaCl, Diamond Periodic arrangement of atoms/ions over a large distance ~1000Å 10,000Å or more AMORPHOUS (Short range order) Glass, polymers (~10-40Å) Entropy Zero (Perfect order ---- Crystal) ΔH should be ve ΔG = -ve

5 Packing of atoms / ions HCP CCP AKG Square close packing (Layer) Hexagonal close packing (Layer) a a a a a a a a a a a a a a a a a a b c a a a a a a a a c (octahedral hole) HCP ABABABAB Tetrahedral b holes

6 Close packed structures: fcc and hcp type ABCABC arrangement fcc ABAB arrangement hcp

7 A B C AKG ABC ABC Cubic Close packing (ccp) Close packed layers are parallel diagonal across one face 74% of the total volume occupied by spheres Layers of spheres in CCP A B C CCP -- 2 tetra 1 oct per sphere Tetrahedral Octahedral Interstices

8 NaCl, CsCl Ionic structures (Radius ratio rules) AKG NaCl (Rock Salt) Zinc sulphide structures CaF 2 (Fluorite) Sphalerite Wurtzite

9 COVALENT SOLIDS Diamond As Sphalerite ZnS AKG C C C C C Graphite C.C.P. of C All tetrahedral sites are occupied by C C Sp 3 hybridized Layered Solid sp 3 hybrid orbitals tetrahedral C Sp 3 hybridized Weak interaction (Vander Waals) Molecular Solids Benzene (L.T.) sp 2 hybrid orbitals ti triangular planar

10 Connectivity of Polyhedra 1 2 AKG Corner connected octahedra Each octahedra other octahedra Each atoms (X) shared by 2 octahedras X (in one octahedra) X 3 Each atom sharing -- 6 octahedra 6 atoms (in one octahedra) ---- X : Not possible Edge- shared octahedra Layers of edge-shared octahedra 4 atoms share 4 octahedra ---Plane 2 atoms unshared (2X) X 3

11 INTRINSIC Defects in Solids EXTRINSIC (impurities) AKG Point defects H G E Extended defects (ordered defects) G=H TS Entropy increases (with defects) G (High T) Minimum shifts to higher defect Concentration (increase in T) Na Cl Cl Na Na Cl Cl Na Cl Defect concentration Na Cl Na Na Cl Cl Na Na Cl Na Cl Na Cl Na Schottky defect (Point defect) Ag Cl Ag Cl Ag Cl Ag Cl Ag Cl Ag Cl Ag Ag Cl Cl Ag Cl Cl Ag Cl Ag Cl Ag FRENKEL Defect (Interstitial & occupied) Overall stoichiometry unaffected equal Nos. of + & - defects ~ 1 defect/10 14 formula unit in NaCl (130 o C)

12 Estimation of defects --- Density measurements AKG TiO Ti : O 1 : 1 ρ = 4.92 g/cc (experimental density) a = 4.18Å Z = 4 Mass = Mass per unit cell = x 4 ρ = M/V = 5.81 g/cm -3 Which is greater than measured ρ Vacancies present Conductivity measurements Extrinsic Point defects As in Si Ca 2+ Y 3+ Zr 4+ Ca in ZrO 2 Y in ZrO 2 Zr Increase in e - O 2- ion vacancies (n-type semiconductor) Ca-stabilised ZrO 2 Y-stabilised ZrO 2 (Solid electrolyte Oxygen ion)

13 Colour Centre (F-center) (Extrinsic point defect) Farbenzenter Na Cl Na Cl Na Cl Alkali halide Heated in vapor of alkali metal Na e Na AKG A e - in halide ion vacancy 1 Cl Na Cl Excitation of e- e- in a box quantized energy levels Colour Extended defects Clustering of defects Line defect Corner-shared octahedra (Point defect) Edge-shared octahedra Crystallographic shear plane

14 --- Variable composition Non-stoichiometry AKG Wuestite FeO (nominal composition) Fe 0.89 O Rock-salt (NaCl structure) Fe 0.96 O TiHx (1 x 2) ZrHx (1.5 < x 1.6) TiOx (0.7 x < 1.25) VOx (0.9 x 1.2) P(O 2 ) P(O 2 ) MO and MO 2 F = C-P+1 = = 0 O/M Non-stoichiometric compound 1 2 O/M F = C-P+1 = = 1 F (No. of degrees of freedom)

15 LAYERED SOLIDS AKG Strongly bonded layers (weak interaction between layers) LiTiNbO 5 (TiO 6 & NbO 6 octahedra forming layers) Ion-Exchange Intercalation Li ions Graphite, FeOCl, TaS 2 LaCoO 2 Clays: montmorillonite LiNbTiO 5 Hydrotalcites Uncharged layers Negatively charged layers -- cations Positively charged layers -- anions

16 INTERCALATION REACTIONS AKG Reactions of Solids General molecule or ion inserted into a Solid lattice Layered structures: (No major change in structure of solid) 1. Strong Covalent network of atoms remains unchanged 2. Vacant sites interconnected Diffusion of Guest species Natural Van der Waals interaction between layers interlayer space empty lattice sites Charged compounds weak electrostatic force interlayer sites partially or completely filled with TaS 2 RNH 2 Exponential of lattice

17 INTERCALATION of K in Graphite AKG Staging of Graphite -ve charged K + C (graphite) + K (vapour) (64 o C) First stage (all inter layer sites are filled) C 8 k C 8 Br Layers are +vely charged C 24 k 2 nd 3 rd C 36 k 4 th C 48 k

18 Natural Zeolite ZEOLITES evolve water (heated) ZEO to boil Lith Stone [M n+ ] x/n [AlO 2 ] x [SiO 2 ] 1-x Framework Structures (mainly Aluminosilicates) Cavities Channels for charge balance Tetrahedra of Al,Si,B,P Linked together (MO 4 ) Be,Ga,Ge BeGa Ge Lowenstein s Rule Al O Si Al O Al membered ring (tetrahedra)

19 O 2- Sodalite cage (β cage) Al 3+ /Si & 4 membered rings Building Blocks for other Zeolites Joining 4, 6 or 8 - membered rings to other rings

20 Zeolite A Sodalite cages Linked by 4 membered rings Faujasite Six membered linker

21 Properties of Zeolites : 1. Absorption of small molecules (size and shape selective). Zeolite A water/ not ethanol. More Al +3 / Si +4 ratio More cation Zeolite A (1:1) - Better absorption of hydrophiles Hydrophobic Zeolite (high Si +4 content) Absorbs non-polar, benzene etc.

22 2. Ion Exchange (Wide application) Na Zeolite A + ½ Ca +2 Ca 0.5 Zeolite A + Na + 3. Catalysis : H Zeolites (Acidic derivatives) (Removes hardness of water Water softening Radioactive Sr +2 / Cs + removal) H Si O+ H Al O Si + H + O O O Al 600C -H 2 O Al Si + _ Si O Al O O Lewis acid Si Si (Electron pair acceptor) Bronsted acid (Proton donor)

23 Rearrangements / Dehydration (Isomerization) Shape selective catalysis Shape selective catalysis Example. CH 3 -C 6 H 5 -CH 3

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25 Rock Salt Structure (NaCl-type) TRANSITION METAL OXIDES TiO NiO (First row transition metal oxides) ReO 3 O 2- AKG 14 5 Ti 4+ Perovskite Structure (ABO 3 ) A 12 coordinated B 6 coordinated ReO 6 octahedra; corner connected BO 6 octahedra; (T. metal ion - B) BaTiO 3 CaTiO 3 LaMnO 3

26 From Bonds (Molecules) to Bands (Solids) Antibonding AKG s s Bonding Formation of n molecular orbitals from n atomic orbitals Conduction band Band gap Valence band material Band gap (ev) C (diamond) 6 Insulators NaCl 9 (High band gap) Si 1 Ge 0.7 GaAs 1.4 n Semi-conductors (Metals partially filled bands)

27 300K Copper : 10 7 Ohm -1 cm -1 Metal Doped silicon (n or p) : 10 2 Ohm -1 cm -1 Silicon : 10-7 Ohm -1 cm -1 Diamond : 10-9 Ohm -1 cm -1 Nylon : 10-9 Ohm -1 cm -1 Resistivity Mica : Ohm -1 cm -1 PVC : Ohm -1 cm -1 Insulator

28 Metals/ Semiconductors/ Insulators AKG Ability to conduct electricity Flow of electrons (holes) Band gap low (intrinsic i i semiconductor) Doping P in Si (n- type) Al in Si (p- type) Extrinsic semiconductor C-Band V-Band p doped in Si n-type Ef = Fermi energy (Fermi edges) C-Band Si Al level (Al C-Band is lower than Si) C-Band p-type V -Band R = ρl/a Ef Mtl Metal Semiconductor (Partially filled band) Ef Resistan nce Mtl Metal Semiconductor superconductor Temperature (K)

29 Resistan nce SUPERCONDUCTIVITY Kammerlingh Onnes 1911 (Nobel 1) s.c Metal Semiconductor Ideal Superconductors Zero Electrical Resistance (Perfect Conductor) Zero Magnetic Induction (Perfect Diamagnet) Macroscopic quantum phenomena Superconductivity electrical resistance Superfluidity viscosity Temperature (K) Levitation effect Meissner effect 100 years of superconductivity

30 APPLICATIONS OF SUPERCONDUCTORS 1. Medical Industry MRI Exploits the high magnetic fields expelled by superconducting wires for medical applications 2. Transportation Industry Superconductor coils create strong magnetic fields that produce the effect of levitation 500 miles per hour / small consumption of energy 3. Electric Power Industry HTS power cables can carry two to ten times more power in equally or smaller sized cables

31 Applications of Inorganic Solids LiMn 2 O 4 Spinel Battery material LaNi 5 Hydrogen storage material PbTe Thermoelectric Zeolite Catalysts Mol. sieves Cu 1-X S (spintronics)

32 ZrW 2 O 8 (0.3K to 1050K) Strong isotropic thermal expansion from 20 to 425K. NTE is based on the transverse thermal motion of oxygen in M-O-M M linkages. Some polyhedra corners are linkage free Network of corner-sharing ZrO 6/2 octahedra and WO 4/2 tetrahedra. A. W. Sleight et al. J Solid State Chem, (2003)

33 Can Solid Breathe??? Exhibits almost a reversible doubling (85%) of its cell volume while fully retaining its openframework topology. Nanoporous iron(iii) carboxylate (MIL-88) a b c Atomic displacements larger than 4 Å are observed when water or various alcohols are adsorbed in the porous structure. Displacive transition occurs during the swelling phenomenon (X-ray thermodiffractometry). 9.26Ǻ 11.18Ǻ 13.87Ǻ Contracted as-synthesized open forms G. Ferey et al. JACS (2005)