Low temperature crystallization of lead zirconate titanate thin films by asol-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 e lectron microscopy (TEM). A metastable Pt3Pb intermetallic phase has been i dentified. The formation of this metastable phase was found to depend on th e drying temperature, the thickness of the as-deposited film, annealing tem perature, and annealing time. Perovskite PZT was found to nucleate on top o f the intermetallic phase, rather than directly on Pt. The improved lattice match between the intermetallic ( a(0) = 4.05 Angstrom) and perovskite PZT ( a(0) = 4.035 Angstrom) as compared to between Pt(a(0) = 3.9231 Angstrom) and the perovskite is believed to substantially reduce the activation energ y for the nucleation of perovskite on Pt. Using this effect, (111) perovski te PZT has been grown at a temperature as low as 440 degrees C. The formati on of the intermetallic phase is believed to facilitate the (111) film orie ntation. The growth kinetics of the PZT were analyzed using the Avrami mode l, and from this, the crystallization activation energy was determined as 1 79 kJ/mol for the phase transformation from pyrochlore to perovskite for th is materials system. TEM examination and measurement of electrical property indicated that the films crystallized at 480 degrees C were good quality, with a pyroelectric coefficient of 1.8X10(-4) C m(-2) K-1 and a remnant pol arization of 24 mu C m(-2). (C) 1999 American Institute of Physics. [S0021- 8979(99)00910-X].