Fast three-step method for shear moduli calculation from quartz crystal resonator measurements.

Research paper by C C Behling, R R Lucklum, P P Hauptmann

Indexed on: 05 Feb '08Published on: 05 Feb '08Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control


Quartz crystal resonator measurements can be used for polymer material characterization. The non-gravimetric regime of these resonators is exploited: the electrical response of polymer-coated quartz resonators depends on the polymer shear modulus. Previously reported methods employ an electrical admittance analysis together with difficult and time-consuming data fitting procedures to calculate the film shear modulus. This contribution presents a fast and accurate three-step method for the calculation of complex shear moduli of polymer films from quartz crystal resonator measurements. In the first step, the acoustic load impedance is calculated from the electrical admittance of the quartz crystal. The key point of this method is the application of a family of approximations for the calculation of the shear modulus from the acoustic load impedance in the second step. In the third step, the best approximation is improved further in an iterative procedure.