Prof. Yoo has a strong research background on high temperature superconductor. After he joined our school in 1988, he has expanded his research interests to magnetic materials, transition metal oxides, and electroceramics. Current research topics in the field of high temperature superconductor consist of bulk-type devices for a large scale application and coated conductors for the next generation superconducting cable. In the field of magnetic materials, rare earth-based magnets for high performance permanent magnets and magnetic thin films for microwave devices are under investigation. For transition metal oxides, his group is performing researches on fabrication and characterization of high-quality single crystals and thin films. Finally, electroceramics such as the cathode materials for the Li-ion battery and microwave dielectrics have also been studied. In many topics, he is performing research in collaboration with industry and other research groups.