Relaxor single crystals PZN-9%PT have been cut and poled along [ 1 101] direction for which the spontaneous polarization P s is approximately parallel to the poling field E p . The piezoelectric matrix of the monoclinic single-domain (1M state) has been determined, in the approximation of an orthorhombic symmetry. The shear mode (15) along [101], gives the highest electromechanical coupling factor k 15 (>80%) and the largest piezoelectric coefficient d 15 ($3200 pC/N). The properties of the disoriented 1M state have been calculated from a change of axes. The maximum of d ' 33 is obtained along a direction close to [001]. This is due to the very large value of d 15 compared to d 33 in the basic 1M state. On the other hand the transverse piezoelectric coefficient along [uv0] for the [001] disoriented P s single domain presents a strong anisotropy. Finally, in the [001] domain engineered configuration, an important extrinsic contribution of the domain coexistence is evidenced by comparing calculated and measured coefficients.

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