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Full-Text Articles in Engineering
Origin Of Interfacial Polar Order In Incipient Ferroelectrics, Yijia Gu, Nan Wang, Fei Xue, Long-Qing Chen
Origin Of Interfacial Polar Order In Incipient Ferroelectrics, Yijia Gu, Nan Wang, Fei Xue, Long-Qing Chen
Materials Science and Engineering Faculty Research & Creative Works
There are ample experimental evidences indicating that the ferroelastic domain walls of incipient ferroelectrics, such as SrTiO3 and CaTiO3, are polar. The emergence of such interfacial polar order at a domain wall is exciting and believed to arise from the coupling between a primary order parameter, such as a strain or an antiferrodistortive (AFD) order parameter, and polarization. There have been several mechanisms proposed to explain the emergence of interfacial polar order, including biquadratic coupling, AFD-antiferroelectric coupling, and flexoelectric coupling. Using CaTiO3 as an example, we demonstrate, using both asymptotic analytics and numerical calculation, that the …
Orientations Of Low-Energy Domain Walls In Perovskites With Oxygen Octahedral Tilts, Fei Xue, Yijia Gu, Linyun Liang, Yi Wang, Long-Qing Chen
Orientations Of Low-Energy Domain Walls In Perovskites With Oxygen Octahedral Tilts, Fei Xue, Yijia Gu, Linyun Liang, Yi Wang, Long-Qing Chen
Materials Science and Engineering Faculty Research & Creative Works
Many applications of ferroic materials, such as data storage and spintronics, are achieved through the control and manipulation of their domain wall (DW) orientations and configurations. Here we propose a rotational compatibility condition to identify low-energy DWs in perovskites with oxygen octahedral tilt instability. It is derived from the strong DW energy anisotropy arising from the rigidity and corner-sharing feature of the octahedral network. We analyze quantitatively the DWs in SrTiO3 and explain successfully the unusual ferroelectric DW width and energy in BiFeO3.
First-Principles Study Of 180⁰ Domain Walls In Batio₃: Mixed Bloch-Néel-Ising Character, Menglei Li, Yijia Gu, Yi Wang, Long-Qing Chen, Wenhui Duan
First-Principles Study Of 180⁰ Domain Walls In Batio₃: Mixed Bloch-Néel-Ising Character, Menglei Li, Yijia Gu, Yi Wang, Long-Qing Chen, Wenhui Duan
Materials Science and Engineering Faculty Research & Creative Works
The 180⁰ ferroelectric domain walls (FDWs) have long been regarded as purely Ising type in ferroelectrics, but recent theoretical works suggested that they can also have Néel- and/or Bloch-like rotations. Using a combination of first-principles calculations with phase-field simulations, we studied the 180⁰ FDWs on different crystallographic planes in prototypical ferroelectric perovskite BaTiO3. The polarization profiles of 180 FDWs on (100) and (410) planes revealed that the (100)- and (410)-FDWs both exhibit Néel-like character besides their intrinsic Ising character, while the (410)-FDW also simultaneously shows a Bloch-like oblique of ~6 nm, as a consequence of the deviation of …
Monoclinic Phases Arising Across Thermal Inter-Ferroelectric Phase Transitions, Yijia Gu, Fei Xue, Shiming Lei, Tom T. A. Lummen, Jianjun Wang, For Full List Of Authors, See Publisher's Website.
Monoclinic Phases Arising Across Thermal Inter-Ferroelectric Phase Transitions, Yijia Gu, Fei Xue, Shiming Lei, Tom T. A. Lummen, Jianjun Wang, For Full List Of Authors, See Publisher's Website.
Materials Science and Engineering Faculty Research & Creative Works
Thermotropic phase boundaries (TPBs), as thermal analogs of morphotropic phase boundaries (MPBs), are associated with the thermal inter-ferroelectric phase transitions. Similar to an MPB, a TPB exhibits a characteristically flattened energy profile which favors polarization rotation, thus giving rise to a structurally bridging low-symmetry phase. We report on the kinetic process of thermal inter-ferroelectric phase transitions in BaTiO3 and KNbO3 using the phase-field method. The domain structures are found to play key roles in stabilizing the monoclinic phase. In simple domain structures, the monoclinic phase is a transient phase and cannot be stabilized into its neighboring phase regimes. …
Flexoelectricity And Ferroelectric Domain Wall Structures: Phase-Field Modeling And Dft Calculations, Yijia Gu, Menglei Li, Anna N. Morozovska, Yi Wang, Eugene A. Eliseev, For Full List Of Authors, See Publisher's Website.
Flexoelectricity And Ferroelectric Domain Wall Structures: Phase-Field Modeling And Dft Calculations, Yijia Gu, Menglei Li, Anna N. Morozovska, Yi Wang, Eugene A. Eliseev, For Full List Of Authors, See Publisher's Website.
Materials Science and Engineering Faculty Research & Creative Works
We show that flexoelectric effect is responsible for the non-Ising character of a 180° ferroelectric domain wall. The wall, long considered being of Ising type, contains both Bloch- and Néel-type polarization components. Using the example of classic ferroelectric BaTiO3, and by incorporating the flexoelectric effect into a phase-field model, it is demonstrated that the flexoelectric effect arising from stress inhomogeneity around the domain wall leads to the additional Bloch and Néel polarization components. The magnitudes of these additional components are two or three magnitudes smaller than the Ising component, and they are determined by the competing depolarization and flexoelectric fields. …
Phenomenological Thermodynamic Potential For Catio₃ Single Crystals, Yijia Gu, Karin Rabe, Eric Bousquet, Venkatraman Gopalan, Long-Qing Chen
Phenomenological Thermodynamic Potential For Catio₃ Single Crystals, Yijia Gu, Karin Rabe, Eric Bousquet, Venkatraman Gopalan, Long-Qing Chen
Materials Science and Engineering Faculty Research & Creative Works
The antiferrodistortive (AFD) structural transitions of calcium titanate (CaTiO3) at ambient pressure have been extensively studied during the last few years. It has been found that none of the AFD polymorphs is polar or ferroelectric. However, it was recently shown theoretically and later experimentally confirmed that a ferroelectric transition in CaTiO3 can be induced by tensile strains. The ferroelectric instability is believed to be strongly coupled to the AFD soft modes. In this paper, we present a complete thermodynamic potential for describing the coupling between the AFD and ferroelectric phase transitions. We analyzed the dependence of transition …