Structural origin of the relaxor-to-normal ferroelectric transition in Pb([Mg.sub.1/3][Nb.sub.2/3][O.sub.3])-xPbTi[O.sub.3]

A relaxor-to-normal, or micro-to-macrodomain, transition in Pb([Mg.sub.1/3][Nb.sub.2/3][O.sub.3])-xPbTi[O.sub.3], is found under electric fields applied along [001] for x>=0.24. The results have shown that an intermediate tetragonal ferroelectric phase is important to the sharpness of this transition, as observed in its dielectric response.