Behaviors of crystallization and nanograin growth in SBT by a sol-gel process

A novel sol-gel process using inorganic salts as starting materials was successfully developed for preparing nano powders of ferroelectric strontium bismuth tantalate (SrBi₂Ta₂O₉, known as SBT) with ethylene alcohol as a solvent and acetic acid (HOAc) as a catalyst. XRD, TEM and TG-DTA were used to analyze the precursor crystalline process. Crystalline samples with different average nanograin sizes ranging from 4 nm to 70 nm were prepared by calcining the dried gel at different annealing conditions. The metal-oxide clusters that embedded in highly polar matrix of mesoporous-carbon are responsible for nano-sized powder synthesis at lower temperature. The dependence of the grain growth behaviors of SBT under conventional furnace annealing (CFA) process on the annealing temperature (T) and time (t) were investigated systematically. By least square fitting, the crystalline and vitreous characteristic energies E_a1=0.709 eV, E_a2=0.093 eV and the two other parameters T₀=814 K (541°C) and Δ=0.022 were obtained.