Piezoelectric Response of Lanthanum Doped Lead Zirconate Titanate Films for Micro Actuators Application
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1129-V11-06
Piezoelectric Response of Lanthanum Doped Lead Zirconate Titanate Films for Micro Actuators Application
Takashi Iijima, Bong-yeon Lee, Seiji Fukuyama National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba central 5, Tsukuba 305-8565, Japan
ABSTRACT La doped lead zirconate titanate (PLZT) films are prepared using a chemical solution deposition process. The effect of La substitution on the piezoelectric response was investigated to clear the possibility of the micro actuator application for the PLZT films. Nominal compositions of the 10% Pb excess PLZT precursor solutions were controlled like La/Zr/Ti= 0/65/35, 3/65/35, 6/65/35, and 9/65/35. These precursor solutions were deposited on the Ir/Ti/SiO2/Si substrates, and the thickness of the PLZT films was 2µm. 10 to 20- µm- diameter Pt top electrodes are formed with a sputtering and a photolithography process. The polarizationfield (P-E) hysteresis curves and the longitudinal displacement curves were measured with a twin beam laser interferometer connected with a ferroelectric test system. With increasing La substitution amount, the P-E hysteresis curves became slim shape, and remnant polarization (Pr) decreased. The hysteresis of the piezoelectric longitudinal displacement curves also decreased with increasing La substitution amount. The amount of the displacement under unipolar electric field showed a peak at La/Zr/Ti= 3/65/35. The calculated effective longitudinal piezoelectric constant (d33eff) is 129.2 pm/V at 3/65/35. This amount was relatively higher than that of PZT films at morphotropic phase boundary (MPB: 0/53/47) composition prepared the same film preparation process. INTRODUCTION In the field of the micro-scale smart systems, high performance piezoelectric film micro actuators are demanded. Therefore, static actuators are well developed as the micro actuator, while the structure of the micro static actuator is very complicated and the driving voltage is relatively high [1]. To overcome these subjects of the micro static actuators, piezoelectric film micro actuators such as lead zirconate titanate (PZT) are investigating [2]. For the PZT film micro devices, large displacement is required and the PZT films are driven with higher electric field than coercive field (Ec) of the film. To develop the piezoelectric micro actuator devices, therefore, low leakage current, better linearity of displacement, and high piezoelectric constant are required for the PZT films. It is well known that a hysteresis of the piezoelectric longitudinal displacement of the lanthanum (La) substitute lead zirconate titanate (PLZT) decrease with increase of lanthanum substitution amount for bulks and thin films [3, 4]. In this study, to clear the possibility of the micro actuator application of the PLZT films, the effect of La substitution for the PZT films on the piezoelectric response were investigated.
Top side interferometer MLD-103 (NEOARK)
Probe Ferroelectric test system
Piezoelectric film sample
FCE (Toyo Corp.)
Substrate
Bottom
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