Owing to unusual chemical versatility and structural intricacy, perovskites can be designed to attain unique electronic, magnetic, ferroelectric, thermoelectric, mixed-conducting, and other properties through selection of the A- and B- site ions, their fractions, ionic sizes and valences, spin states, and orbital orderings, as well as the oxygen content and vacancy ordering. The best-known examples are spectacular high temperature superconducting cuprates, colossal magnetoresistive manganates, ferroelectric titanates, and recently discovered remarkable cobaltites with spin-dependent conductivity and thermoelectric power, and ferrites with dramatic metal-insulator transitions. We will illustrate our systematic exploration of the effects of composition, temperature, pressure, and oxygen content on thermodynamic stability and physical properties of manganites and cobaltites. The focus of this presentation will be on kinetically stable compounds with decreased structural distortions and atomically ordered layered- and double- perovskites with enhanced useful properties.

Supported by the NSF-DMR-0302617 and by the US Departments of Education and Transportation