Neutron powder diffraction measurements and a constitutive model were used to determine the bulk longitudinal and transverse electrostrictive coefficients (Qijkl) for polycrystalline samples of the subject material. Effective single-crystal Qijkl were calculated from the powder neutron diffraction data. The resulting values of the three independent Qijkl, as determined from the cubic symmetry of the underlying lattice, are Q3333 = 2.1×10−2 m4/C2, Q3322 = −0.87×10−2 m4/C2, and Q3232 = 1.2×10−2 m4/C2. Using these effective single-crystal values, a random ensemble average was used to predict the electromechanical performance of the polycrystalline material. Predicted values of bulk Q3333 = 1.86×10−2 m4/C2 and Q3322 = −0.78×10−2 m4/C2 are 89% and 87%, respectively, of the effective single-crystal values for Q3333 and Q3322, while measured values of polycrystalline specimens are only ∼ 70% of the single-crystal values. © 1998 American Institute of Physics.