Low temperature crystallization of lead zirconate titanate thin films by a sol-gel method

Pyroelectric lead zirconate titanate (PZT) thin films have been prepared by a sol-gel method and characterized by x-ray diffraction and transmission electron microscopy (TEM). A metastable ${\mathrm{Pt}}_{\mathrm{3}}\mathrm{Pb}$ intermetallic phase has been identified. The formation of this metastable phase was found to depend on the drying temperature, the thickness of the as-deposited film, annealing temperature, and annealing time. Perovskite PZT was found to nucleate on top of the intermetallic phase, rather than directly on Pt. The improved lattice match between the intermetallic ${\mathrm{(a}}_0\text{=4.05\hspace{0.05em}Å)}$ and perovskite $\mathrm{PZT}{\mathrm{(a}}_0\text{=4.035\hspace{0.05em}Å)}$ as compared to between $\mathrm{Pt}{\mathrm{(a}}_0\text{=3.9231\hspace{0.05em}Å)}$ and the perovskite is believed to substantially reduce the activation energy for the nucleation of perovskite on Pt. Using this effect, (111) perovskite PZT has been grown at a temperature as low as 440 °C. The formation of the intermetallic phase is believed to facilitate the (111) film orientation. The growth kinetics of the PZT were analyzed using the Avrami model, and from this, the crystallization activation energy was determined as 179 kJ/mol for the phase transformation from pyrochlore to perovskite for this materials system. TEM examination and measurement of electrical property indicated that the films crystallized at 480 °C were good quality, with a pyroelectric coefficient of ${\text{1.8×10}}^{\text{−4}} {\mathrm{C m}}^{\mathrm{-2}}{\mathrm{ K}}^{\mathrm{-1}}$ and a remnant polarization of 24 μC m⁻².