ROLE OF DEFECTS IN THE FERROELECTRIC RELAXER LEAD SCANDIUM TANTALATE

Unlike Pb(Mg1/3Nb2/3)O-3 and similar ferroelectric relaxors which neve r truly become ferroelectric at zero-field, disordered Pb(Sc1/2Ta1/2)O -3 (PST) is a relaxer that spontaneously transforms into a ferroelectr ic phase. The control of the degree of order of the B-site cations in PST by appropriate heat treatment has been often used to demonstrate t he influence of chemical disorder on the dielectric properties of ferr oelectrics. Here it is shown that, in PST, disorder itself is not suff icient to prevent a macroscopic ferroelectric transition, and that dis ordered stoichiometric PST exhibits a strong dielectric relaxation, bu t upon cooling it spontaneously becomes a macroscopic ferroelectric. L ead deficiency in disordered Pb(Sc1/2Ta1/2)O-3 prevents this spontaneo us ferroelectric transformation, and the material shows more usual rel axer properties.