STUDY OF THE NON-NBT PHASE IN Sr DOPED NBT THIN FILMS

The morphology, composition and mechanism of the non-NBT phase in the Sr-doped NBT [SNBT, (Na0.5Bi0.5)1-xSrxTiO3] thin films by chemical method were investigated using XRD, SEM, crystallization analysis and thermodynamics analysis. The results showed that the non-NBT phase is the porphyroblastic grains in the matrix and looks like a plate-shaped polyhedron. The mechanism of the non-NBT phase formation is that the Sr2+ and Na+ combined with ${\rm TiO}_{3}^{2-}$ to form initial simple titanate, such as SrTiO3, Na2TiO3, or NBT phase decomposed because of the volatilization of Bi under a higher annealing temperature or longer annealing duration, and then transform into the secondary simple titanates (Sr2+,2Na+)TiO3 or (Sr,Na)xTiyOz. Moreover, the NBT phase disappeared for the SNBT films annealing at temperatures higher than 600°C and for 15 min.