High frequency PZT composite thick film resonators

High frequency, thickness mode resonators were fabricated using a 7 μm PZT thick film which was produced using a modified composite ceramic sol-gel process. Devices were produced and the acoustic properties measured for different electrode sizes ranging from 45 * 45 to 250 * 250 μm². The best electrode size, which maximised the acoustic response and minimised the insertion loss, was found using an area of 110 * 110 μm². This showed a resonant frequency of about 200 MHz, an electro-mechanical coupling coefficient effective of 0.29 and a Q factor of 22. The devices were modelled using a Mason type model which gave good agreement between the experimental data and the simulations. The latter showed for the PZT thick film an electro mechanical coupling coefficient of 0.4 and a stiffness of 8.55 * 10¹⁰ N·m^-2.