Poling relaxor- PbTiO3 single crystals along pseudocubic  results in a macroscopic symmetry of mm2, enabling a large face shear d 36 in Zt±45° cut crystals. In order to allow the determination of electrical properties by the resonance method, square samples are required. Using Pb (In0.5 Nb0.5) O3 -Pb (Mg1/3 Nb2/3) O 3 - PbTiO3 crystals, piezoelectric d36 coefficients were determined to be in the range of 2000-2500 pC/N, with electromechanical coupling factor k36 ∼0.80-0.83. Mechanical quality factor Q∼180 and ultralow frequency constant of ∼500 Hz m were obtained. Together with the wide temperature usage range (up to ∼110 °C) and high ac driving field stability (∼5 kV/cm), such face shear crystals have a promising potential for ultralow-frequency-transducer applications. © 2011 American Institute of Physics.