  The dielectric and structural order-disorder properties of as-sintered
complex perovskite (x)Pb(In1/2Nb1/2)O3:(1-x)Pb(Mg1/3Nb2/3)O3 ceramics are
highly influenced by the quantity of Pb(In1/2Nb1/2)O3 (PIN). High PIN quantity
causes the relative permittivity maxima to decrease and the temperature (Tmax)
to increase. Also, strong frequency dispersion is dominant in the relative
permittivity plotted against the temperature. In the ferroelectric hysteresis
loop measurements, the maximum values of electric displacements (Dmax) decrease
with increasing PIN. The ceramics in the composition range x = 0.1 to 0.8
behave as ferroelectric relaxors and exhibit very slim hysteresis loops for all
these compositions. Transmission electron microscopy (TEM) studies show that
the size of the 1:1 structural ordered domains is influenced by the PIN
quantity. The relationship between the dielectric properties and the long-range
1:1 order in these relaxors appear to be in conflict with the commonly accepted
order-disorder behavior in complex perovskite ferroelectrics, in which large
structural domains correspond with the tendency to depart from the relaxor
state. TEM observations show that individual 1:1 ordered domains in
(x)PIN:(1-x)PMN ceramics are composed of numerous nano-sized ordered domains,
separated by fine antiphase boundaries.
