Ternary single crystals Pb(In0.5Nb0.5)O 3-Pb(Mg1/3Nb2/3)O3-PbTiO 3 with monoclinic phase poled along  direction show single domain state (1O state) with macroscopic mm2 symmetry. The complete set of material constants was determined using the combination of impedance and ultrasonic methods. The thickness shear vibrations in the single domain state give the highest piezoelectric coefficients, with values being on the order of d15 4550 pC/N and d24 4100 pC/N. The rotated value of d33* along , calculated using the single domain data, is in good agreement with the  poled multidomain crystal, being 1790 pC/N versus 2010 pC/N, exhibiting the high longitudinal piezoelectric in multidomain comes from the high shear properties in single domain state, with the extrinsic contribution about ∼11, induced by the phase boundary motion. © 2011 American Institute of Physics.