The role of tio in the perovskite nucleation and (111) orientation selection in sol-gel PZT layers

Abstract

We have proposed a lattice matching mechanism for the selection of (111) PZT orientation, based on the experimental evidence of the formation of cubic TiO on the Pt electrode surface in the earlier stages of thermal processing of PZT layers. Thus, a fining of TiO with Pt and, consequently of PZT (Ti-rich) with TiO (orientation relationship:TiO (111)//Pt(111) and respectively PZT (111)//TiO(111) ) has been evaluated. Similar mismatch degree values were obtained comparatively with the classical cases of intermetallic layer "templates" (for example PtxPb, Pt3 Ti, etc). The very good lattice matching supports the proposed mechanism, consisting in the formation of cubic TiO on Pt and, later, of the nucleation and growth of PZT (tetragonal) of cubic TiO, where is formed. In comparison with the case of TiO2(rutile) matching, previously proposed by other groups, having larger mismatch values, the cube-to-cube orientation relationship could explain the selection of (111) orientation as a major one in some specific conditions affected by some parameters especially related to solution chemistry and thermal processing steps.