STRESS-INDUCED PHASE FORMATION OF PZT 52/48 THIN FILMS

ABSTRACT

In this work, tetragonal and rhombohedral phases in PZT 52/48 thin films were identified using XRD. The relative intensities of these phases were calculated. The presence of the rhombohedral phase may have implications for the piezoelectric properties, since the polar axis in rhombohedral crystals lies along the (111) body diagonal rather than the (001) axis for tetragonal crystals.

The effects of stress on phase co-existence at the morphotropic phase boundary were also investigated. Two PZT52/48 films were grown under the compressive stresses of different magnitudes. For the film grown under smaller compressive stress, two-phase co-existence was observed, but the film grown under larger compressive stress was observed to be rhombohedral dominant. The piezoelectric coefficient, d_33,f of the rhombohedral dominant film was less than that of the mixed-phase film. It is possible that a (001)/(100) oriented film of slightly tetragonal composition (e.g. 48/52) could have higher piezoelectric coefficients than a mixed-phase MPB film.

Keywords:

• PZT thin films
• sol-gel
• stress
• phase formation

ACKNOWLEDGMENT

Authors would like to thank EPSRC for financial support through project GR/S4527/01.