Preparation and dielectric properties of SrBi2Ta2O9 thin films by sol-gel method

Ferroelectric Sr0.7Bi2.2Ta2O9 (SBT) thin films were prepared at 600 and 750 C for 1 h using SBT precursor solutions of metal alkoxides with and without acethylacetone (acac) addition, respectively. Crystalline SBT thin films were successfully prepared at 600 C from precursor solutions without acac. Films prepared at 750 C showed a high (105) diffraction intensity with random orientation, and a bimodal grain structure consisting of stone wall-like grains of 500-860 nm and small grains of 100-300 nm. The addition of acac to precursor solutions promoted a c-axis preferred orientation of SBT. Films with a c-axis preferred orientation showed a bimodal microstructure consisting of large grains of 200-300 nm and small grains of about 50 nm. Films prepared at 750 C from solutions without acac had a dielectric constant of 119, remanent polarisation of 3.1 microcoulombs/cm2, and coercive field of 65.1 kV/cm, while those prepared from solutions with acac had values of 205, 7.2, and 53.3, respectively. 9 refs.