Fabrication of a Laminated Actuator with Excellent Linearity Using Ground Potassium Sodium Niobate-Based Ceramic Sheets

Linearity is an important factor that affects actuator accuracy. However, the high nonlinearity of KNN piezoelectric ceramics restricts their application in actuators. In this study, we used grinding stress to improve the linearity of ceramic chips, and used them to fabricate a laminated actuator. The ceramic sheets were ground to a thickness of 0.5 mm. During grinding,some areas of the ceramic changed from tetragonal to orthorhombic, owing to the grinding stress. The piezoelectric constant (d33) increased from 198 to 268 pC/N. Notably, the linearity of the ceramics improved. Seven pieces of ground ceramics were bound, to fabricate a laminated multilayer actuator with a total thickness of 3.5 mm. A DC voltage was applied to the actuator, and the displacement was measured. The displacement reached 0.73 μm under a low driving voltage of 200 V. A linear regression analysis of the displacement–voltage relationship was performed, obtaining the regression equation of the actuator. The linearity correlation coefficient was approximately 0.9903, implying that the actuator exhibits a high accuracy. The grinding stress improved the linearity, together with the piezoelectric properties of the ceramic chips, thus improving the actuator accuracy. This research will promote the application of KNN piezoelectric ceramics in actuators.