Measurements of LiNbO3 Properties by Multi-parameter Inversion Based on Acoustic Microcopy

This paper expands on a theoretical model between the mechanical and electrical properties with acoustic characteristics to obtain the theoretical dispersion curve for Y-cut LiNbO3 piezoelectric plate. The experimental dispersion curve of the LiNbO3 plate is extracted via V(f,z) analysis through defocusing measurements based on an acoustic microscopy and a lens-less line focusing transducer. The objective function of the inversion depends on the experimental dispersion curve. The inversion method adopts a hybrid particle-swarm-based simulated-annealing (PS-B-SA) optimization, which is used for joint inversion of the mechanical and electrical parameters of LiNbO3. The theoretical dispersion curve will approach the experimental dispersion curve by constantly modifying the mechanical and electrical parameters in the theoretical model: the elastic constants (C (11), C (12), C (22), C (23), C (25), C (55)), piezoelectric constants (e (11), e (12), e (26), e (33)), and dielectric constants (epsilon (11), epsilon (22)). The inversed series of constants are those who make the theoretical dispersion curve most fit the experimental ones. The results show that the inversed mechanical and electrical parameters agree well with the reported values, and the stability and accuracy of the inversion is acceptable. This research provides a useful tool to characterize the mechanical and electrical properties of piezoelectric materials simultaneously.