Compositional Substitutions and Aliovalent Doping of BaTiO3-Based Thin Films on Nickel Foils Prepared by Chemical Solution Deposition

Several strategies were evaluated focusing on the optimum reliability of thin-film ceramic capacitors derived from different compositions based on BaTiO3 (BT) and prepared by chemical solution deposition onto nickel foils. Film crystallization was carried out at 800 degrees C under reducing conditions to prevent the detrimental oxidation of the metal electrode while allowing the formation of the pure perovskite phase. In a first approach, compositional modifiers were introduced into the system, yielding to Ba(Ti0.7Zr0.3)O-3 (BTZ) and (Ba0.7Sr0.3)TiO3 (BST) solid solutions. Despite the lower permittivities obtained with respect to pure BT, dielectric losses and leakage current densities in these films were observed to improve. With the aim of further optimizing these features, the second approach focuses on the defect chemistry of BST films by incorporation of either donor-acceptor cations (Mn2+ and Nb5+) or single rare-earth elements (Dy3+ or Y3+ "magic ions") into the perovskite. The leakage conduction in the associated capacitors is revealed to effectively decrease in the first case, whereas doping with rare-earth cations does not substantially improve the dielectric properties of the ceramics. Processing effects related to the thin-film configuration, rather distant from the classical scenario used within the technology of multilayer bulk ceramic capacitors, also account for the final properties obtained in the films of this work.