Structures and colossal dielectric behavior of Na1/3Ca1/3La1/3Cu3Ti4O12 ceramics fabricated via a sol-gel process

The dielectric response of a novel giant dielectric ceramic with good dielectric and electrical properties, Na1/ 3Ca1/3La1/3Cu3Ti4O12, was investigated in this work. This ceramic, with a perovskite-like structure, was successfully synthesized using a sol-gel method. Fine-grain ceramics were found in all sintered specimens. These ceramics produced large dielectric permittivities, 9.89 x 103-1.04 x 104, and low dielectric loss tangent values of 0.040-0.057. First-principles calculations indicated that Na+ is substituted at the Cu2+ sites. Additionally, La3+ likely occupies Ca2+ sites. Experimental and computational techniques demonstrated the presence of an oxygen vacancy in the Na1/3Ca1/3La1/3Cu3Ti4O12 lattice that results in generation of Cu+ and Ti3+. The IBLC phenomenon and small polaron hopping between valence electrons of Cu and Ti ions have been recognized as the causes of the giant dielectric behavior of these materials.