Dielectric phase-transition and polarization studies in stepped and compositionally graded lead magnesium niobate-lead titanate relaxor thin films

Abstract

Ferroelectric properties of chemically heterogeneous multilayers and graded composition thin films of (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃, a well-known relaxor, were prepared using a multitarget pulsed laser ablation system. Target materials with different values of x (0.0, 0.1, 0.2, and 0.3) were used for ablation growth. Films with sharp interfaces and graded interfaces were prepared and were characterized for their electrical properties. The stepped films were found to have a phase-transition behavior dominated by the individual layer behavior with their corresponding local dielectric maxima. The graded films showed an overall averaged effect of the system. The graded films showed an enhanced diffusiveness in the phase transition and the γ value was found to be 2.43, which is a measure of diffusivity. The tunability of these graded films was found to be high around 60% and was twice that of any of the film of homogeneous composition films. The room-temperature polarization hysteresis curves exhibited slim loop characteristics with a saturation polarization of about 40 µ C/cm² in the case of both stepped and graded films.