Defect chemistry and optimized dielectric properties of Ni1-δO ceramics via doping donor ions

As a candidate for colossal permittivity (CP, >104) materials, NiO has been widely concerned and studied. Regrettably, high dielectric losses hinder its continued development and the CP origin is controversial. For this work, the design of single-doped donor ions is used to reduce the dielectric loss of the Ni1-δO CP ceramic. Besides, the triggered defect chemistry is discussed. The results show that the grain size gradually decreases with the doping of Ti ions increases. Additionally, the dielectric loss decreases by two orders of magnitude and the resistivity is improved while a CP is maintained when 0.01 ≤ x ≤ 0.03. Based on the structural characterization and simulate computation, it is proposed that the appearance of secondary phase increases the resistance of the grain boundary and forms the interfacial barrier layer, and the charge compensation effect effectively reduces the hole concentration and improves the grain boundary and grain resistances due to partial Ti ions dissolving in the Ni1-δO lattice, which is thought to be responsible for the reduced dielectric loss. This work shows the optimized dielectric properties and mechanism of single-doped Ni1-δO ceramics, and some problems and ideas of Ni1-δO CP ceramics are summarized, which can give researchers some inspiration and promote the development of CP ceramics.