Mechanisms controlling phase formation in PZT thin films

Factors controlling the formation of the perovskite phase in sol-gel prepared PZT film were studied. Perovskite was found to form quite easily, even in very thin films on sapphire, polycrystalline Al ₂O₃ and NaCl but only in relatively thick films on quartz, glass and Si. Formation of the perovskite phase is also favoured in (a) films with low Zr/Ti ratio and high Pb content, (b) films heated rapidly to annealing temperature and (c) films annealed in N₂ ambient. RBS studies show that large deficiency of Pb develops in films which remain in the pyrochlore structure due to reaction at the interface or due to diffusion into the interface. The initial transformation from amorphous to pyrochlore is believed to be due to enhanced strain energy barrier for the amorphous→perovskite transformation