  Structure of the morphotropic phase and the phase coexistence region has been
investigated in (1-x)Bi(Mg1/2Zr1/2)O3-xPbTiO3 ceramics. The structure is cubic
with space group Pm3m for the compositions with x<0.57 and tetragonal with
space group P4mm for the compositions with x>0.59. For the compositions with
0.56<x<0.60, both the tetragonal and cubic phases coexist, which suggest very
narrow morphotropic phase boundary region of compositional width
{\Delta}x~0.03. Rietveld refinement of the structure using x-ray diffraction
data confirms coexistence of the tetragonal and cubic phases in the MPB region
and rules out the coexistence of tetragonal and rhombohedral structure reported
by earlier workers. After poling appearance of significant value of
electromechanical coupling coefficient in the cubic compositions (x=0.55, 0.56)
suggests the presence of electric field induced transition from centrosymmetric
cubic phase to noncentrosymmetric phase. Polarization- Electric field
hysteresis loop measurement on the cubic composition with x=0.56 gives well
saturated loop similar to that observed in Pb(Mg1/3Nb2/3)O3 relaxor below the
freezing temperature.
