Electrical properties and mechanical stress of thick plasma-sprayed Pb(Zr0.58Ti0.42)O3 coatings

Abstract

Ferroelectric thick PZT coatings have been produced with rhombohedral crystalline structure by plasma-spraying of PZT powder (x = 0.58) and post-deposition thermal treatment. The correlation of the crystalline phase composition and the morphological structure with the electrical properties was studied in dependence on deposition conditions and post-deposition thermal treatment. The mechanical stress was also determined. Its origin and its relationship to the electrical properties was investigated. Due to the partial decomposition of the PZT powder particles, a typical as-deposited coating consists of two tetragonal perovskite phases together with crystalline ZrO2 und PbO. Annealing at 850 °C results in well homogenized coatings, which only consist of PZT grains of the rhombohedral phase. The dielectric constant ψ of the films increases to about 60 to 70% of the bulk value and the coatings are polarizable with remanent polarization of 2 to 3 m̈C/cm2. The stress in the plasma-sprayed PZT coatings is low and compressive. The total stress in as-sprayed coatings, deposited onto preheated substrates, is found to be about -100 MPa. Intrinsic compressive stress of about -20 to -40 MPa is estimated. The biaxial modulus of the film Ef/(1 - n̈f) is determined to be 121 GPa, which is very close to the value of the bulk material (118 GPa).