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Solid State ChemistryCHEM 6182

A. P. WilkinsonSchool of Chemistry and Biochemistry

Georgia Institute of TechnologyAtlanta, Ga 30332-0400

Course outline� An overview of the synthesis and

applications of inorganic materials� Structure and compound identification in

the solid state� Electrical and ionic conductivity� Zeolites as selective catalysts, sorbents and

ion exchangers

Objectives� To provide an introduction to the concepts

underlying solid state chemistry� To illustrate the wide range of materials and

physical properties that currently available

Why Solid State Chemistry?� Many aspects of modern life are dependent

upon the availability of functional solids� Chemists are in a strong position to contribute

to their syntheses – However, the chemist needs to be able to

understand what they are trying to make and why

Properties of interest� Optical

– Non-linear optics, lasers, phosphors etc..� Electrical

– Conductivity and response to stimuli� Magnetic

– Data storage, electromechanical devices� Structural� Catalytic� Etc.

Optical properties� Non-linear optical materials play an

important role in data transmission and storage– LiNbO3, KTiOPO4,KH2PO4

� Laser materials– semiconductors and laser host crystals

� Phosphors– for displays and imaging

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NLO Materials and Second Harmonic Generation

� NLO materials can be used to double the frequency of laser radiation- Useful as short wavelength

lasers can be difficult to make

� Short wavelength radiation better for information storage and transmission

Semiconductor blue lasers

Color centers� Exposure to radiation can induce defects

– Useful for imaging– Useful for dating

KBr KCl NaCl

Electrical properties� Useful electrical properties include

– superconductivity– semiconductors– ceramic metals for electrodes– response to stimuli e.g. heat and pressure– dielectric properties– ionic conductivity for electrochemical cells– conversion of heat or light to electrical power

� Interesting properties include– low dimensional behavior

K2[Pt(CN)4]Br0.3.3H2O� Is a one dimensional metal

– has a high conductivity in one direction only– when viewed under polarized light it looks

metallic for one polarization and transparent for another

– why ?

K2[Pt(CN)4]Br0.3.3H2O viewed with transmitted polarized light

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K2[Pt(CN)4]Br0.3.3H2O viewed with polarized reflected light

The packing of Pt(CN)4 units in K2[Pt(CN)4]Br0.3.3H2O

From Peters et al. Inorg. Chem. 15, 782 (1976).

Superconductors� Many materials are superconducting

– however, until 1986 all superconductors had critical temperatures < 30 K

� Superconductors find application in magnet construction

� High Tc superconductors are just starting to be used– initially in MRI and cell phone base stations

Levitating a magnet over YBCO

The structure of YBa2Cu3O7 Superconducting detector for MRI

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Semiconductors� Methods such as Chemical Vapor

Deposition are of great importance in the semiconductor industry

� Chemists play a vital role in the development of compounds that can be used in CVD

Ionic conductivity� Solids that are capable of conducting ions

are used in the fabrication of electrochemical cells– oxygen sensors in automobiles– electrolytes in fuel cells– electrolytes in high energy density batteries

Magnetic materials� Data storage� Transformers and motors� Data read out

– state of the art disk drives employ Magneto Resistive materials in the drive heads

� Shaft seals– ferrofluids can be confined in the area to be

sealed using magnetic fields

Ferrofluids

Ferroelectric materials� Crystals can have electric dipole moments just like

molecules� If the direction of the dipole moment can be flipped by

an applied field the material is said to be ferroelectric

Shape selective catalysts� Zeolites offer a way of carrying out

chemistry in very confined spaces� The type of chemistry that can be done is

determined by the pore sizes that can be made– entirely reliant upon a chemists skills

� Great industrial importance– gasoline cracking

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Ion exchangers� Zeolites and related solids can be used as

convenient ion exchangers� Zeolite A is used as a water softener in all

powder laundry detergents in the U.S.� Zeolites are used for radioactive waste

clean up

Zeolite A

Zeolite L and Offretite Inorganic materials synthesis

� Very different from molecular synthesis– Usually can not purify solid product– Synthetic techniques are different

» high temperature preps» ion exchange reactions» intercalation / insertion processes» vapor transport» sol-gel» Chemical Vapor Deposition (CVD)