Diffuse phase transition in Nb-doped BaTi2O5 thin films

BaNb x Ti 2–x O 5 (x = 0, 0.002, 0.004, 0.006, 0.008, 0.01) thin films were deposited on the Pt(111)/Ti/SiO 2 /Si substrates using the sol–gel method. The effect of Nb 5+ substitution on the electric properties of BaNb x Ti 2–x O 5 films was investigated. Diffuse phase transition was observed in all the thin films. The relationship between the dielectric constant and temperature of these films showed a wide platform and no frequency dependence. For the film with x = 0.006, an abnormally broadened dielectric platform was obtained in the temperature range of 200–400 °C, and its value fluctuated in the range of 350 ± 10. The research showed that Nb-doped and thermal stress contributed greatly to this abnormally broadened platform of ε(T) curve. The substituting Nb 5+ in BaTi 2 O 5 thin films caused small microscopic composition fluctuation, which enhanced the degree of diffusion phase transition of the films. And the thermal stress on the films caused inhomogeneous polarization of the surface and center of the films, resulting in a change in phase transition behavior. In addition, the BaNb x Ti 2–x O 5 thin films with high dielectric constant at high temperatures were successfully obtained, which were beneficial to the application of BaTi 2 O 5 films under high temperature conditions.