PZT Multilayer Actuators Research Articles

Fine grained textured BaTiO3-based piezoelectric ceramics with outstanding strain properties for the lead-free multilayer actuator

Textured BaTiO3-based piezoelectric ceramics show the excellent application potential as their piezoelectric characteristics almost approach the commercial lead-based ceramics. Piezoelectric multilayer actuators (MLAs) with low driving voltages and compact structures are great in line with the equipment trend of miniaturization and functional integration. However, the coarse textured grains result in few grain layers in each thin ceramic layer of MLAs, hardly guaranteeing the electromechanical dependability. In this work, we combined the composition regulation with a modified template grain growth (TGG) to prepare fine-grained textured ceramics. The Zr4+ and Sn4+ co-substituted (Ba0.95Ca0.05)(Ti0.94Zr0.05Sn0.01)O3 (BCZTS) was chosen as the matrix composition. Unreacted BaCO3 (BC, 7.3 % in content) was artificially introduced into matrix to realize the partial reaction template grain growth (RTGG), reducing textured grains from 9.7 μm to 6.9 μm. Textured BCTZS-BC MLAs achieved high texture degree of 92 % and further smaller grain size of 3.4 μm at 1300 °C, due to inhibition on mass transfer and improvement on thermal conductivity of Pt electrodes. The high strain of 0.12 % in textured MLAs is almost 2.3 times enhancement compared to non-textured counterparts, and the ultralow strain hysteresis Hs of 5.6 % at 30 kV/cm is equivalent to that in PZT MLAs. The microscopic coercive voltage is 3.1 V with a maximum displacement of 210 p.m., which is mainly ascribed to the smaller domain sizes and the favorable “4O” domain configuration in textured MLAs.

Thermochemical Reactions Between PZT and Ag/Pd Powders: Relevance to Cofiring of Multilayer Actuators

Mixtures of Ag1−xPdx (x=0.2, 0.3) and doped PZT ceramic powders have been heat treated in air and the resulting phase content has been analyzed by X‐ray diffraction and transmission electron microscopy. Beginning around 400°C, a phase similar to PbPdO2 is formed on the surface of the Ag1−xPdx particles and subsequently decomposes at temperatures <700°C. Consequently, the remaining Ag1−xPdx powder becomes significantly silver‐rich while the reaction progresses. After decomposition the Pd appears to realloy and the initial Ag1−xPdx composition is recovered. We show that the reaction is all but eliminated in a nitrogen atmosphere. The occurrence of this reaction was also investigated in PZT multilayer actuators cofired with Ag0.7Pd0.3 electrodes. Transmission electron microscope analysis revealed the presence of distinct crystallites at the electrode–ceramic interface, most likely nucleated from a PbO liquid phase arising from the decomposition of PbPdO2.

Effect of grain sizes on piezoelectric properties of multilayer thick film actuators

A unique piezoelectric multilayer thick film actuator for computer hard disk drives has been designed and fabricated using the screen printing technology. Dielectric and piezoelectric properties of such PZT thick film actuators with grain sizes ranging from 0.8 to 3.0 μm have been investigated. Under an applied electric voltage of 6V. displacement values of 0.25 μm, 0.44 μm, and 0.55 μm and corresponding resonance frequencies of 58.0 kHz, 61.4 kHz, and 65.6 kHz are obtained in those PZT multilayer actuators with grain sizes of 0.8 μm, 1.3 μm, and 3.0 μm, respectively. The correlation between processing parameters with grain sizes and piezoelectric properties is discussed.

Fabrication and characterization of PZT multilayer actuators

Multilayer actuators with sixty 165-μm-layers (6.5 mm × 6.5 mm × 10 mm) of lead zirconate-titanate (PZT-4D) were made and tested to determine their possible use for low voltage electromechanical uses. These actuators were fabricated via tapecasting and cofired with integral platinum electrodes. After firing, external lead wires were attached for poling, testing, and final use. Such multilayers require 4 MV/m. The high capacitance of the actuators results in a measured transition from capacitive to inductive behavior at high frequency (∼850 kHz) as the actuator becomes electrically resonant with typical test leads.