Electrical and electromechanical characteristics of LTCC embedded piezoelectric bulk actuators

Piezoelectric effect is a versatile method to generate force and movement in microsystems as well as electrical feedback in sensors and smart packages. On the other hand, low temperature cofired ceramic (LTCC) has been utilised as a base material for hybrid circuit boards, packages as well as some microfluidic devices; however, new means to introduce integrated functionalities for it are needed. In this paper, a 10×5 mm rectangle and 10 mm in diameter round PZT samples fully embedded and cofired with Heraeus HeraLock LTCC were manufactured and their hysteresis, dielectric, displacement and microstructure properties and coupling factors were characterised. Relative permittivity of the LTCC embedded varied from 1300 for the rectangle sample to 1500 for the round sample at 1 kHz, while r of 2209-2406 was obtained for corresponding bare bulk samples respectively. Measured piezoelectric d 33 coefficient was in the range of 324-441 pm V−1 for embedded structures, while 553-567 pm V−1 was obtained for free bulk samples at 100 Hz. Results show that LTCC has significant impact for electromechanical performance mainly due to constraining of the LTCC layers. In spite of this, feasible figures of merits were obtained for LTCC embedded PZT materials, while further improvements can be obtained by optimising the process and structures for LTCC based microsystems, sensors and actuators.