Effects of annealing temperature and time on the structure and ferroelectricity of sol-gel-derived Ba_0.8Sr_0.2TiO₃ thin films from highly diluted precursor solutions

Ba_0.8Sr_0.2TiO₃ thin films were prepared from a high dilute precursor solution by a sol-gel process using a layer-by-layer heat treatment method. The annealing temperature ranged from 600 to 700 degree(s)C and the annealing time ranged from 5 to 15 min. Analysis by X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy showed that the annealing temperature and time strongly affected the structure of the films. The crystallinity and grain size of the films increased with the annealing temperature increasing. The grain size of the films annealed at 700 degree(s)C increased from 80 to 200 nm when the annealing time increasing from 5 to 15 min, and the film annealed at 700 degree(s)C for 15 min showed a pure columnar structure. Electrical measurements showed the ferroelectricity of the films annealed at 700 degree(s)C became better with the annealing time increasing. The film annealed at 700 degree(s)C for 15 min showed a remnant polarization of 3.5 (mu) C/cm² and a coercive field of 83 kV/cm.