  The piezoelectric face-shear (d36) mode may be the most useful shear mode in
piezoelectrics, while currently this mode can only exist in single crystals of
specific point groups and cut directions. Theoretically the d36 coefficient
vanishes in piezoelectric ceramics because of its transversally isotropic
symmetry . In this work, we modified the symmetry of poled PZT ceramics from
transversally isotropic to orthogonal through ferroelastic domain switching by
applying a high lateral stress along the "2" direction and holding the stress
for several hours. After removing the compression, the piezoelectric
coefficient d31 is found much larger than d32. Then by cutting the compressed
sample along the zxt+45 deg direction, we realized d36 coefficients up to 206
pC/N which is measured by using a modified d33 meter. The obtained large d36
coefficients in PZT ceramics could be very promising for face-shear mode
resonators and shear horizontal (SH) wave generation in nondestructive testing.
