Dielectric and Piezoelectric Properties of PZT 52/48 Thick Films with (100) and Random Crystallorgraphic Orientation
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Dielectric and Piezoelectric Properties of PZT 52/48 Thick Films with (100) and Random Crystallorgraphic Orientation Q. F. Zhou, E. Hong, R. Wolf, and S. Trolier-McKinstry Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802 ABSTRACT Ferroelectric Pb(Zr1-xTix)O3 (PZT) films have been extensively studied for active components in microelectromechanical systems. The properties of PZT films depend on many parameters, including composition, orientation, film thickness and microstructure. In this study, the effects of crystallographic orientation on the dielectric and transverse piezoelectric properties of Pb(Zr0.52Ti0.48)O3 (PZT 52/48) films are reported. Crack free random and highly (100) oriented PZT(52/48) films up to ~ 7 µm thick were deposited using a sol-gel process on Pt (111)/Ti/SiO2/Si and Pt(100)/SiO2/Si substrates, respectively. The dielectric permittivity (at 1kHz) for the (100) oriented films was 980-1000, and for the random films ~ 930-950. In both cases, tanδ was less than 0.03. The remanent polarization (~ 30 µC/cm2) of random PZT films was larger than that of (100) oriented PZT films. The transverse piezoelectric coefficient (d31(eff)) of PZT films was measured by the wafer flexure method. The d31(eff) coefficient of random PZT thick films (-80pC/N) was larger than that of (100) oriented films (-60pC/N) when poled at 80 kV/cm for 15 min. INTRODUCTION Recently, there has been an increasing interest in ferroelectric lead zirconate titanate (PZT) films because of their wide range of applications in microelectronics, microelectromechnical systems (MEMS) and ultrasonic imaging. Potential applications include membrane sensors [1], micro-accelerometers [2] and micro-motors [3]. In general, these devices are based on films of thicknesses less than 1 µm. However, applications based on piezoelectric films are not limited to the realm of microdevices, and some potential applications require more thick films that have large piezoelectric coefficients and high energy densities. Therefore, PZT thick films are of interest. There are a number of groups which have successfully fabricated PZT system thick films. Tsuzuki et al. [4] prepared PLZT thick films by multiple electrophoretic deposition and sintering processing. Sayer et al. [5] have reported the thick PZT ceramic coating using a sol-gel based ceramic-ceramic 0-3 composites. Cross et al. [6] prepared the PZT thick films by modified solgel process using acetic acid route. Milne et al. [7] also fabricated the PZT thick films using titanium diisopropoxide biacetylacetonate as raw materials. However, preparing thick uniform PZT films with large area by the sol-gel technique is still challenging due to cracking that results from large stresses between the substrate and film. In this paper, crack-free sol-gel PZT thick films with the morphotropic phase boundary (MPB) composition of Pb(Zr0.52Ti0.48)O3 (PZT 52/48) were deposited on Pt(111)/Ti/SiO2 and Pt (100)/SiO2/Si substrates, respectively. The dielectric and piezoelectric propert
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