Theoretical Basis And Application Of Interferometric Method In Measuring Piezoelectric Coefficient

Piezoelectric material is a kind of compound which can realize the mutual conversion of electrical energy and mechanical energy.It is widely used in nondestructive testing,dynamic sensing,medical imaging and other technical fields.Piezoelectric coefficient is an important index to evaluate the performance of piezoelectric materials,and its accurate calculation directly affects the application of piezoelectric materials in various piezoelectric devices.Therefore,the accurate measurement of piezoelectric parameters is of great significance for the development and application of piezoelectric materials.At present,the characterization methods of piezoelectric constants mainly include static method,quasi-static method,resonance method and ultrasonic method.These methods can characterize the piezoelectric coefficients to some extent,but have their own limitations.The static method has relatively low measurement accuracy.The resonance method is easy to be interfered by the uncorrelated vibration mode,which has high requirements on sample size and is difficult to directly determined the symbol of piezoelectric coefficient.The ultrasonic method is mainly used to evaluate the elastic constant,while the piezoelectric coefficients need further calculation.Therefore,it is nesseary to find a direct and effective method to charactererize the piezoelectric coefficients for accurately evaluating the performance parameters of piezoelectric materials.In view of the shortcomings of the existing testing methods,this paper analyzes the influencing factors of the interferometric method in the measurement of piezoelectric coefficients,and explores the feasibility of the interferometric method for the piezoelectric coefficient characterization.On the basis of studying the inverse piezoelectric effect for trigonal crystal system,the measurement of piezoelectric coefficient by interferometric method is verified by the combination of simulation and experiment tests,and the sample dimensional conditions suitable for interferometric measurement were given.The interferometric method has also been promoted and verified in the piezoelectric measurement for low symmetry crystals.The main work includes:1.The theoretical basis of interferometric method was analyzed.The factors influencing the crystal deformation were discussed and the dimension conditions of the inverse piezoelectric deformation for interferometric measurement.The possible errors in the experiment were discussed and the corresponding solutions were provided.2.The inverse piezoelectric deformation of LiNbO3(LN)and La3Ga5.5Ta0.5O14(LGT)crystals with trigonal symmettry was studied by COMSOL simulation.Crystal cuts suitable for piezoelectric coefficient evaluation using interferometric method were discussed,which provides theoretical support for the sample design in the actual testing process.3.According to the simulation studies,the suitable LGT and LN crystal cuts were designed and tested with the interferometric method.Compared with the reported results,the piezoelectric coefficients determined by interferometric method shows good accuracy,exhibiting the advantages in testing the value and symbol of the piezoelectric coefficients.4.Promote the interferometric method to the evaluation of piezoelectric coefficients of ?-BiB3O6(BIBO)crytal with monoclinic phase.Crystal cuts were designedand the independent piezoelectric coefficients of BIBO crystal were determined.Based on the obtainedresults,the inverse piezoelectric deformation of BIBO crystal was simulated,which in good agreement with the experimental results.It was proved that the interferometric method also possessed good adaptability and accuracy in the piezoelectric measurement for thelow-symmetry crystals.