VARIABLE STRUCTURAL ORDERING IN LEAD SCANDIUM TANTALATE-LEAD TITANATEMATERIALS

A phase region of variable order-disorder [VOD] has been identified in this study for compositions in the range [x = 0.0-0.075] (x: mole fra ction PbTiO3). Materials from this region retain some degree of long-r ange ordering of B-site cations as evidenced by x-ray and electron dif fraction which is enhanced with post-sintering annealing. Annealed cer amics exhibit sharp dielectric responses [K(T)] and near-normal first- order ferroelectric behavior while as-fired specimens with lesser degr ees of long-range ordering show the more diffuse and dispersive charac teristics of a relaxer ferroelectric.