Chalcogen, Lanthanoid, Rare earth, Energy gap for direct transition

• Ce-O
• Cu-La-O
• Cs-Tb-Te-Zn
• Co-La-O
• Eu-O
• rare earth
• lanthanoid
• chalcogen
• non-disordered
• transitional
• tetragonal
• orthorhombic
• cubic
• trigonal
• hexagonal