Due to the inherent crystallographic anisotropy of piezoelec-tric materials83as well as various types of available vibrationalmodes, the piezoelectric coefficient tensor is of the third rankand relates second rank mechanical and first rank electrical vari-ables. During operation one of these variables denotes the inputsignal and the other denotes the output signal. The key exam-ples of these properties include piezoelectric charge or straincoefficients (dij), piezoelectric voltage or strain coefficients (gij),electromechanical coupling coefficients (kij), and mechanicalquality factor (Qm), which are shown here in reduced notation orVoigt notation.83Tables 3 and 4 outline a number of applicationsand their respective figures or merit.