MEASUREMENT OF THE ELECTROSTRICTIVE COEFFICIENTS OF MODIFIED LEAD MAGNESIUM NIOBATE USING NEUTRON POWDER DIFFRACTION

Neutron powder diffraction measurements and a constitutive model were used to determine the bulk longitudinal and transverse electrostrictiv e coefficients (Q(ijkl)) for polycrystalline samples of the subject ma terial. Effective single-crystal Q(ijkl) were calculated from the powd er neutron diffraction data. The resulting values of the three indepen dent Q(ijkl), as determined from the cubic symmetry of the underlying lattice, are Q(333)=2.1x10(-2) m(4)/C-2, Q(3322)=-0.87x10(-2) m(4)/C-2 , and Q(3232)=1.2x10(-2) m(4)/C-2. Using these effective single-crysta l values, a random ensemble average was used to predict the electromec hanical performance of the polycrystalline material. Predicted values of bulk Q(3333)=1.86x10(-2) m(4)/C-2 and Q(3322)=-0.78x10(-2) m(4)/C-2 are 89% and 87%, respectively, of the effective single-crystal values for Q(3333) and Q(3322), while measured values of polycrystalline spe cimens are only similar to 70% of the single-crystal values. (C) 1998 American Institute of Physics.