Polymorphic and morphotropic phase transitions in Pb(Mg1/3Nb2/3)O3–PbTiO3 solid solutions

Abstract

Study of evolution of ferroelectric correlations in a system which intrinsically exhibits short range polar order in the form of polar-nano regions (PNRs), is the goal of the present work. For this purpose, well-known Relaxor ferroelectric i.e. PbMg1/3Nb2/3O3(PMN) and its solid solutions with PbTiO3(PT) has been systemically synthesized by varying composition, precursors and synthesis parameters. Dynamics associated with the PNRs and structural phase transitions of various polymorphs have been traced through temperature and frequency dependent dielectric permittivity profile. Formation of solid solutions with PT generates ferroelectric correlations associated with the tetragonal polymorphs, suppresses thermal fluctuations, overcomes diffused character of phase transition, effects polarization switching, stabilizes ferroelectric hysteresis characteristics and shifts dielectric permittivity maxima toward higher temperatures. Addition of PT led to relaxation dynamics associated with the multiple polymorphic phase transitions for T < 500 K, where system exhibits intrinsic character. Polymorphs with low symmetries lies below freezing temperature, where structural phase transition generates polar order. Diffusivity and activation energy of phase transitions, and freezing temperatures of polar regions of various processes have been quantified and compared as a function of PT. Excellent ferroelectric response of the compositions lying in the vicinity of the Morphotropic phase boundary composition has been observed.