ELECTRICAL-PROPERTIES AND MECHANICAL-STRESS OF THICK PLASMA-SPRAYED PB(ZR0.58TI0.42)O-3 COATINGS

Ferroelectric thick PZT coatings have been produced with rhombohedral crystalline structure by plasma-spraying of PZT powder (x=0.58) and po st-deposition thermal treatment. The correlation of the crystalline ph ase composition and the morphological structure with the electrical pr operties was studied in dependence on deposition conditions and post-d eposition thermal treatment. The mechanical stress was also determined . Its origin and its relationship to the electrical properties was inv estigated. Due to the partial decomposition of the PZT powder particle s, a typical as-deposited coating consists of two tetragonal perovskit e phases together with crystalline ZrO2 and PbO. Annealing at 850 degr ees C results in well homogenized coatings, which only consist of PZT grains of the rhombohedral phase. The dielectric constant epsilon of t he films increases to about 60 to 70% of the bulk value and the coatin gs are polarizable with remanent polarization of 2 to 3 mu C/cm(2). Th e stress in the plasma-sprayed PZT coatings is low and compressive. Th e total stress in as-sprayed coatings, deposited onto preheated substr ates, is found to be about -100 MPa. Intrinsic compressive stress of a bout -20 to -40 MPa is estimated. The biaxial modulus of the film E(f) /(1-v(f)) is determined to be 121 GPa, which is very close to the valu e of the bulk material (118 GPa).