1. Other Ionic Structures. Perovskite:“ABO 3 ” B-site BO 6 octahedra A-site 12 Oxygen neighbors For perfect cube: A-O/B-O = √2 “Goldschmidt tolerance factor” Flexible & tolerant: smaller A (A-O/B-O < √2): tilting Very large number of examples

2. Perovskite: most widely studied oxide structure Wide range of chemistries possible - thousands of examples known - high T c cuprate superconductors - Colossal Magneto-Resistance (La,SrMnO 3 ) - fast ion conduction (Li +, O 2- ), batteries, fuel cells - mixed electronic/ionic conduction, fuel cells - oxidation/reduction catalysts - ferroelectric / piezoelectric ceramics (BaTiO 3, Pb(ZrTi)O 3 ) - important mineral structure in lower mantle (MgSiO 3 ) - frequency filters for wireless communications : Ba(Zn 1/3 Ta 2/3 )O 3 Unique properties of perovskites :

3. Dipoles in BaTiO 3 - ferroelectric - piezoelectric Pole sample to align dipoles Many applications: non-volatile memories; sensors, actuators, ultra-sonic imaging Write using nano-tips Memories/nano-lithography

4. High Temperature Superconductors: CuO based Zero electrical resistance to ~ 135K

5. La 3+ Mn 3+ O 3 Replace by Sr 2+ each substituted Sr oxidizes Mn 3+ to Mn 4+ “mixed valent” Mn show unique electronic/magnetic properties

6. ZSM-5: silicate based microporous solids; Catalysts; Molecular sieves; chemical separation