Transition-metal oxides show lots of interesting and useful properties. They include ferroelectrics, ferromagnets, conductors, batteries, and so on. These materials are widely used in current electronic devices. The wide variety of their crystal structures gives rise to various electronic structures, which lead to interesting and useful physical and chemical properties. We are focusing on the fundamental physics and chemistry of these "Functional oxides" and seeking new materials with new functions. We are conducting systematic studies of material synthesis based on phase equilibrium information. Precise crystal structures are analyzed by x-ray and neutron diffraction. Electronic and magnetic structures are discussed based on the results of electronic structure calculations and physical property measurements.


Novel functional oxides

In transition metal oxides, the cation-d-orbital and anion-p-orbital are strongly hybridized. Competitive and/or cooperative energies of Coulomb interaction, band-width, and exchange interaction also play an important role in giving rise to a wide variety of physical and chemical properties. Such exotic properties could be useful for the functions of electronic devices. There are many examples of such functional oxides: Li-ion batteries are Li-containing Co- or Ni-oxides, and FeRAMs (ferroelectric random access memories) used in IC cards consist of Pb(Zr,Ti)O3 or Bi-containing Ta oxides. Recent significant developments in x-ray and neutron diffraction techniques enable us to determine the detailed crystal structures of such oxides. The information about the structures provides a basis for electronic structure calculations. Therefore, we discuss the relationships between the fundamental physics and useful functions of the functional oxides.