Keller besrest

• Fe-S
• Ba-Ca-Cu-La-O-Y
• Ba-Ca-Cu-La-O
• structural properties
• electronic and electrical properties
• conductivity or resistivity
• structural transitions
• phase transitions
• chalcogen
• transitional
• disordered
• metal
• conductor
• hexagonal
• tetragonal
• orthorhombic
• trigonal