Abstract
Phase morphology and corresponding piezoelectricity in ferroelectric solid solutions were studied by using a phenomenological theory with the consideration of phase coexistence. Results have shown that phases with similar energy potentials can coexist, thus induce interfacial stresses which lead to the formation of adaptive monoclinic phases. A new tetragonal-like monoclinic to rhombohedral-like monoclinic phase transition was predicted in a shear stress state. Enhanced piezoelectricity can be achieved by manipulating the stress state close to a critical stress field. Phase coexistence is universal in ferroelectric solid solutions and may provide a way to optimize ultra-fine structures and proper stress states to achieve ultrahigh piezoelectricity.
Highlights
To explore the role of stress-induced phases on the enhancement of piezoelectricity, we focus on the most commonly used coefficient d33 of each different phase induced by the uniaxial stress XT and shear stress XR
Under shear stress state XR, the R phase keeps stable with only small change of the polarization amplitude since it is equivalent to a normal stress along [111]
Phase coexistence in solid solution systems was studied within the framework of the LandauDevonshire phenomenological theory
Summary
Understanding the origin of high electromechanical coupling and giant piezoelectric response in perovskite-like solid solutions is of both physical and technological importance, especially for the innovation of new generation Lead-free piezoelectric materials.[1,2,3,4] The high electromechanical coupling in the classical perovskite solid solution PbZr1-xTixO3 (PZT) was attributed to the existence of a morphotropic phase boundary (MPB) separating the rhombohedral and tetragonal phases,[5] and later to the existence of the monoclinic (M) phase as a bridge phase between the rhombohedral (R) and tetragonal (T) phases.[6,7] It is generally believed that such an easy polarization rotation path gives giant piezoelectric response in ferroelectric solid solutions with PZT-like MPB.[8]. The large increase of piezoelectricity in relaxor based ferroelectrics could be a critical phenomenon assisted with the elastic stress field and fine structures dominated by the charge-disordered random fields.[26,27,28] The question is what kind of phase structures are there in the MPB systems and how they related with the piezoresponse In this theoretical analysis, we will use a purely homogeneous Landau-Devonshire free energy to analyze the coexisting possibility of R and T phases in the MPB region. Piezoelectricity with respect to each possible phase was calculated and compared
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