Piezoelectric Response of Lanthanum Doped Lead Zirconate Titanate Films for Micro Actuators Application

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 2 mu m. 10 to 20- mu m- diameter Pt top electrodes are formed with a sputtering and a photolithography process. The polarization-field (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 (d(33)eff) 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..