Microstructure and electrical change in CaCu3Ti4O12 induced by Mn doping

Abstract

Mn-doped CaCu3Ti4O12 ceramics prepared by solid-state reactions have been investigated. XRD patterns show that the main peaks are assigned to the CaCu3Ti4O12 phase with body-centered cubic structure, and the remaining peaks are attributed to the diffraction peaks of secondary phase CaTiO3 and CuO. The diffraction peaks of CuO phase are observed suddenly when x ≥ 0.6. As the Mn content increases, the segregation of Cu-rich boundary phase increases gradually. The electrical properties reveal that as the Mn content increases, the electron hopping between Mn ions is transferred from Mn2+/Mn3+ to Mn3+/Mn4+. The value of resistivity increases at first and then decreases, which should be attributed to the coexistence of CaTiO3, oxygen vacancy, and Cu-rich phase. The values of resistivity (ρ200), material constant (B200/600), and activation energy (Ea) of the negative temperature coefficient (NTC) thermistor ceramics are in the range of 3.55 × 103–1.69 × 106 Ω cm, 3570–6889 K, and 0.308–0.594 eV, respectively.