Section 1C Ceramics CrysalStructure
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Section 1C Ceramics CrysalStructure

Course Number: MATE 210, Spring 2007

College/University: Cal Poly

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Section 1 Crystalline Structure CERAMICS (Smith: Chapter 11.1-11.3) The term ceramic comes from Greek (keramikos) "burnt stuff" ....often form ceramics by high temp heat treatment process called firing.... MATE 210 Ceramic Structures - compounds b/w metal and nonmetal ions rather than atoms: + cations - anions - ionic bonds - more complex structures than metals 2 types of ions more ionic more...

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1 Section Crystalline Structure CERAMICS (Smith: Chapter 11.1-11.3) The term ceramic comes from Greek (keramikos) "burnt stuff" ....often form ceramics by high temp heat treatment process called firing.... MATE 210 Ceramic Structures - compounds b/w metal and nonmetal ions rather than atoms: + cations - anions - ionic bonds - more complex structures than metals 2 types of ions more ionic more covalent MATE 210 IONIC BONDING & STRUCTURE CaF2: Ca2+ + cation Fanions F- Charge Neutrality: --Net charge in the structure should be zero. --General form: AmXp AX Zinc Blende, NaCl, CsCl AX2 Flourite ABX3 -- Perovskite m, p determined by charge neutrality MATE 210 COORDINATION # & IONIC RADII Coordination # increases with arrange around a cation? Coord # 2 3 4 6 8 NaCl (sodium chloride) CsCl (cesium chloride) rcation Issue: How many anions can you ranion rcation ranion < .155 .155-.225 .225-.414 .414-.732 .732-1.0 ZnS (zincblende) MATE 210 Bonus Problem What type of crystal structures would CaxFy, CaxOy & GaxAsy form? [Hints] a. charge balance (cation-anion) AnXn b. geometric considerations (ionic radius) Coordination Number Ca = 0.100 nm F = 0.133 nm O = 0.140 nm Ga = 0.062 nm As = 0.185 nm MATE 210 1. Rock Salt (NaCl): Common Ceramic Structure 2 types of ions CN = 6 Two overlapping FCC lattices: cations anions MATE 210 Ceramic Density Computation density = (n cations/unit cell x AWcation) + (n anions/unit cell x AWanion) ____________________________________ Vc NA a Vc = a3 = (2 rNa+ + 2 rCl-)3 = ( 4 x 22.99 ) + ( 4 x 35.45 ) = 2.14 g/cm3 [ 2(0.102 x 10-7) + 2(0.181 x 10-7)]3 (6.023 x 1023) MATE 210 2. Cesium Chloride (CsCl): (Cu-Zn brass) Cl- Cs+ CN = 8 Not BCC crystalline structure.....2 types of atoms! Challenge: determine lattice constant, a ? MATE 210 3. Zinc Blende (ZnS): (SiC) CN = 4 (covalent bonding) 2 types of ions if all same element: diamond cubic (C, Si, Ge) 2 different elements: Zn Blende (ZnS, SiC) MATE 210 4. Perovskite (CaTiO3 ): PbZrO3 piezoelectric YBa2Cu3O7 superconductors 3 types of ions Piezoelectric - converts mechanical Into strain electrical energy Smart Material MATE 210 5. Silicate Ceramics Ratio Si:O atoms 1:2 Low density = 2.65 g/cm3 But strong Si-O bond = high Tm (more covalent character) Silica (SiO2) Cristobalite Polymorph - 3 Crystalline forms Tridymite Quartz MATE 210 Non-crystalline Fused silica or Glass add CaO,Na2O,B2O3,Al2O3 Tmp Quartz 1710 oC Borosilicate 1250 oC Soda lime 860 oC MATE 210 Transmission of Light MATE 210 Uses Thermal insulation Magnetic memory cores Ceramic Compounds Al2O3, MgO Zn(Fe)Fe2O4, CoMn2O4 CaTiO3, SrTiO3, Ln2Ti2O7, Ln2Sn2O7, Cd2Ta2O7 Si3N4, ZrO2 Tl1+xTa1+xW 1 x O6 ((0 < x 1.0 ),TlNb2O6+xF 1 x (0.5 x 1.0) B-Al2O3 ZnO, SiC, MnFe2O4, Ln2V2O7, Y2Mo2O7, LaVO3, LaMnO3, La(NiW)O3, Ln2Pd2O7, Hg2B2O7 V2O3, MoO2, Pb2Ru2O7, Bi2Ru2O7, Bi2Ir2O7, Cd2Re2O7, CaMoO3, LaTiO3, LaNiO3, SrVO3, SrRuO3 La2-xSrxCuO4, YBa2Cu3O7, Bi2Sr2Ca1Cu2O8, Tl2Ba2Ca2Cu3O10 : Insulators High temperature materials Ionic conductors Semi conducting materials Electrically conducting materials Superconductiong materials High temperature heating LaSrCrO3, MoSi2 elements MATE 210 Uses Ferri and ferroelectric materials Piezo and ferroelectric materials Soft and hard magnetic materials Polycrystalline substrates High temperature ceramic capacitors Rocket nose and rocket throat Nuclear fuel Cladding materials Shielding materials Electro-optic materials Cutting tools Ferrite permanent magnets Inorganic colorant Ceramic Compounds PbTiO3, LiNbO3, PLZT, Pb(Fe,Nb )O3, Pb(Co,N)O3 SiO2, BaTiO3, PLZT, Bi4Ti3O12 Fe3O4, Zn(Mn)Fe2O 4, BaFe12O19, LuMnO3 Al2O3 for thick film hybrid circuits PLZT. BaTiO3, Bi4Ti3O12 E-glass, SIALONS UO2, UO2-PuO2 C, SiC, B4C SiC, Al2O3, C1B4C PLZT, LiNbO3, LaAlO3 Al2O3, TiC, TiN ZnO.Fe3O4, Fe3O4, NiO.Fe2O3 Ce2S3 MATE 210 Quick Check 1. How do ceramic structures balance charge and coordination number 2. What are the basic crystal structures of ceramics 3. Discuss the structure of silicate ceramics (crystalline and noncrystalline) 4. Calculate the theoretical density of ceramic structures 5. What are the main differences in the crystal structures of metals vs. ceramics MATE 210
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