Tantalum penta-glycolate sol as a precursor of strontium bismuth tantalate ferroelectric thin films

A sol-gel synthesis method based on the diol route is reported here for the fabrication of strontium bismuth tantalate (SBT, SrBi2Ta2O9) ferroelectric thin films. A tantalum penta-glycolate (TPG)-based sol is synthesized, which is air stable and has low toxicity. The structure of the TPG compound is studied by nuclear magnetic resonance (NMR) spectrometry, and the results show that TPG contains a tantalum cation bonded to five diol groups. The molecular association of the TPG derivatives in the sol, through the terminal hydroxyl groups of the diol ligands, is responsible for its transformation into a gel. Other metal compounds can be easily added to the TPG-based sols for the preparation of air-stable and precipitate-free multicomponent solutions. These solutions are precursors of complex oxide materials. In this paper, SBT thin films have been prepared by this sol-gel method. These films develop a layered perovskite structure after crystallization. The films have a remanent polarization of P-r similar to 10 mu C/cm(2), a coercive field of E-c similar to 65 kV/cm, and are fatigue free up to similar to 10(10) cycles.