Large dielectric tunability of (Ce,Fe)-codoped (Ba,Sr)TiO₃ thin film annealed at low temperature

(Ba_0.6Sr_0.4)_0.99Ce_0.01(Ti_0.99Fe_0.01)O₃ (BSTCeFe) ferroelectric thin film with final annealing temperature at 600 °C was deposited on ITO/glass using a sol–gel method and the annealing time adopted was in the range of 0–12 h. The microstructure, insulating and dielectric characteristics were investigated as a function of annealing time. X-ray diffraction indicates that each film can be well crystallized into single perovskite structure. All the BSTCeFe examples show dense and smooth surfaces without any cracks and the grain size increases with the increase of annealing time. The dielectric tunability for BSTCeFe film is gradually increasing with the increase in the electric field. For the BSTCeFe thin film annealed for 8 h, a maximum value for dielectric tunability is 48% when the electric field of ±600 kV/cm is applied, which can be attributed to the bigger grain size and the relatively low leakage current. Furthermore, the dielectric constant, dielectric loss as well as figure of merit of 378, 0.01 and 40 can be obtained at the frequency of 100 kHz, respectively. These findings indicate that (Ce,Fe)-codoped (Ba,Sr)TiO₃ thin film annealed at the low temperature of 600 °C for 8 h has improved electrical performance for applications in microwave dielectric devices.