Piezoelectric properties of the c-axis oriented Pb(Zr,Ti)O3 (PZT) thin films were investigated. The PZT films with a composition near the morphotropic phase boundary were epitaxially grown on (100)Pt-coated MgO substrates by rf-magnetron sputtering. The PZT films exhibited excellent ferroelectricity with a remanent polarization more than 50 μC/cm2. In order to examine intrinsic piezoelectric properties, cantilever structures were microfabricated with the PZT films. The piezoelectric coefficient d31 of PZT films, which were not subjected to poling treatments, was measured directly from the transverse expansion of the cantilever beams. The measurements revealed that the PZT films were naturally polarized and had a relatively large piezoelectric coefficient d31 of 100×10−12 m/V without poling.
Crystallographic structure of as-grown epitaxial Pb͑Zr,Ti͒O 3 ͑PZT͒ films was investigated with regard to the Zr/Ti ratio and crystalline orientation. PZT films with ͑001͒ and ͑111͒ orientation were epitaxially grown on ͑100͒ and ͑111͒SrTiO 3 substrates respectively using radio-frequency ͑rf͒ sputtering. Four circle x-ray diffraction measurements revealed that the crystallographic dependence on Zr/Ti composition in PZT films was much different from bulk PZT. In particular, ͑001͒-oriented PZT films showed tetragonal structure even in the Zr/Ti composition of 70/30 where the bulk PZT ceramics are rhombohedral phase. In addition, although ͑001͒-oriented PZT films with Zr/Ti ratio of 53/47 and 70/30 showed tetragonal structure, ͑111͒-oriented PZT films with the same Zr/Ti ratio were identified as the rhombohedral structure. The cell volume of the PZT films with both orientations increased, suggesting the excess Pb atoms in the films due to the impinging energetic sputtered particles induces the anomalous crystalline structure of the PZT films. Dielectric properties of the PZT films exhibited stable value independent of Zr/Ti ratio and characteristic increase of dielectric constant near Zr/Tiϭ53/47 could not be observed. These results suggest that the internal stress due to the sputter deposition plays an important roll in the unique characteristics of crystallographic and electrical properties of the epitaxial PZT films.
Preparation of (001)-oriented Pb(Zr,Ti)O(3) (PZT) thin films and their applications to a sensor and actuators were investigated. These thin films, which have a composition close to the morphotropic phase boundary, were epitaxially grown on (100)MgO single-crystal substrates by RF magnetron sputtering. These (001)-oriented PZT thin films could be obtained on various kinds of substrates, such as glass and Si, by introducing (100)-oriented MgO buffer layers. In addition, the (001) oriented PZT thin films could be obtained on Si substrates without buffer layers by optimizing the sputtering conditions. All of these thin films showed excellent piezoelectric properties without the need for poling treatment. The PZT thin films on the MgO substrates had a high piezoelectric coefficient, d(31), of -100 pm/V, and an extremely low relative dielectric constant, epsilon(r), of 240. The PZT thin films on Si substrate had a very high d(31) of -150 pm/V and an epsilon(r) = 700. These PZT thin films were applied to an angular rate sensor with a tuning fork in a car navigation system, to a dual-stage actuator for positioning the magnetic head of a high-density hard disk drive, and to an actuator for an inkjet printer head for industrial on-demand printers.
The midline retroperitoneal approach for AAA was associated with fewer postoperative gastrointestinal and wound complications than the midline transperitoneal approach. Over the long term, there was no wound complication such as abdominal bulge and wound pain in any of the patients.
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