Transmission Electron Microscopy Study of Mod Plzt and Pnzt Thin Films

Both La and Nd–doped PZT, i.e., PLZT and PNZT, ferroelectric thin films were prepared by the metalorganic deposition (MOD) process. The precursor solutions used were derived from lead acetate, lanthanum acetylacetonate, neodymium acetate, zirconium n–propoxide, and titanium iso–propoxide. The dopant concentration of the films analyzed by electron microprobe indicated a one–to–one correspondence between film composition and the composition of the precursor from which the film was made. In this study, the effects of Nd and La dopants in PZT films on Curie temperature was determined by in–situ hot–stage TEM and compared with those of bulk materials. Lattice parameter and phase transformation were determined by both X–ray and electron diffraction. Our observations were: (1) Curie temperature decreases with increasing dopant concentration for both thin foils and bulk ceramics, (2) for a given dopant concentration, Curie temperature and crystal tetragonality of PNZT thin foils is lower than those of PLZT samples, (3) Curie temperature of thin foils was found to be less than those of the corresponding bulk materials, and (4) ferroelectric domains is easily observed in both PLZT and PNZT TEM specimens prepared by the spin–coating method.