Novel poling method in piezoelectric ceramics opens the door to the next-generation large-strain actuators

A piezoelectric actuator, a precisely controlled micro-displacement device driven by an electric field, has broad applications in many areas, such as medical equipment and robotics. However, because the most widely used ferroelectric ceramics based actuators suffer from small output strains, large-size actuators, for example, long, hundreds-layered piezoelectric injectors in automobile engines, are common.

In Journal of Applied Physics, a group of Chinese researchers report having developed a novel periodically orthogonal poling method in the widely-used piezoelectric ceramic—lead titanate zirconate (PZT) that realizes actuation strain of nearly 0.6 % — about four times larger than existing PZT actuators.

The researchers applied high voltage in vertical or horizontal directions to periodically pole a soft PZT sample in different regions, to induce orthogonal poling directions in adjacent poling domains. Then, the researchers applied a unipolar vertical electric field to the whole sample and measured the electric induced actuation using a laser displacement sensor.

Lead researcher Faxin Li of Peking University explained when an electric field is applied on a poled ferroelectric ceramic along the poling direction, a small reversible strain can be induced via the piezoelectric effect. If the electric field is perpendicular to the original poling direction, a large switching strain will be generated due to the non-180^° domain switching, but since the strain is irreversible, scientists considered it to not offer practical applications.

The researchers’ method for the first time realizes a reversible, large domain switching strain that keeps quite stable after 10⁴ cycles of electric loading, applicable for smaller, cheaper low-frequency large-strain actuators such as compact piezo-injectors in low-emission automobile engines. Li’s group is now developing a multi-layer actuator based on the periodically poled PZT ceramics, in which the maximum actuation strain can always be employed.

Source: “Giant actuation strain nearly 0.6% in a periodically orthogonal poled lead titanate zirconate ceramic via reversible domain switching,” by Faxin Li, Qiangzhong Wang, and Hongchen Miao, Journal of Applied Physics (2017). The article can be accessed at https://doi.org/10.1063/1.4997940 .