The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Long-qing Chen - One of the best experts on this subject based on the ideXlab platform.
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Theory of strain phase separation and strain spinodal: Applications to ferroelastic and ferroelectric systems
Acta Materialia, 2017Co-Authors: Yanzhou Ji, Long-qing ChenAbstract:Abstract In the well-known phase decomposition process, a phase with a homogeneous composition separates into two phases with different local compositions that can be geometrically determined by the Common Tangent Construction on the molar free energy versus composition curves. Here we consider an analogous phase destrain process in which a phase with a homogeneous strain separates into two phases with different local strains that can be geometrically determined by the Common Tangent Construction on the volume free energy density versus strain curves. There is also a complete analogy between compositional and strain spinodals. Within the phase destrain model, we provide a general thermodynamic formulation for the phase rule, lever rule, equilibrium conditions of chemical potential, and coherent/incoherent strain spinodals. Using the cubic to tetragonal ferroelastic/ferroelectric transition as an example, we study the possible strain phase separation and spinodal phenomena, and calculate the strain-strain and strain-temperature phase diagrams for the first-order proper, first-order improper, and second-order improper ferroelastic transitions. The proposed phase destrain theory complements the existing compositional phase separation theory and can serve as guidance for the analysis and design of multi-domain/multi-phase structures during any phase transitions associated with structural changes.
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Strain phase separation: Formation of ferroelastic domain structures
Physical Review B, 2016Co-Authors: Fei Xue, Jinxing Zhang, Long-qing ChenAbstract:Phase decomposition is a well-known process leading to the formation of two-phase mixtures. Here we show that a strain imposed on a ferroelastic crystal promotes the formation of mixed phases and domains, i.e., strain phase separation with local strains determined by a Common Tangent Construction on the free energy versus strain curves. It is demonstrated that a domain structure can be understood using the concepts of domain/phase rule, lever rule, and coherent and incoherent strain phase separation, in a complete analogy to phase decomposition. The proposed strain phase separation model is validated using phase-field simulations and experimental observations of $\mathrm{PbTi}{\mathrm{O}}_{3}$ and $\mathrm{BiFe}{\mathrm{O}}_{3}$ thin films as examples. The proposed model provides a simple tool to guide and design domain structures of ferroelastic systems.
Y.j.m. Brechet - One of the best experts on this subject based on the ideXlab platform.
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Equilibrium and diffusion in coherent multilayers
Acta Materialia, 1996Co-Authors: Gary R. Purdy, Y.j.m. BrechetAbstract:Abstract A thermodynamic treatment is presented of isothermal phase equilibria and diffusion in coherent planar multilayers. For two-component systems, coherent two-phase equilibrium compositions can often be generated using the familiar procedure in which a line is constructed doubly Tangential to the coherent free energy functional(s). Only in special cases, however, are the phase equilibria so generated independent of the average composition (for unsupported multilayers) or the substrate effective composition (for multilayers coherently attached to a substrate). The Common Tangent Construction is extended to ternary solution systems, and conditions for which the coherent ternary equilibria are independent of the average or substrate compositions defined. The formal thermodynamic aspects of diffusion in binary and ternary solids are reviewed, and the expected effects of coherency strain on the diffusional homogenization process outlined. The diffusion formalism can often be extended to account for coherency strains simply by substituting the coherent free energy density for its incoherent counterpart. In ternary and higher order systems, it is always possible to choose an initial condition that is free of strain; it is not in general possible to maintain this strain-free condition during the course of diffusional homogenization. The general effect of strain energy on ternary diffusion is to rotate the diffusion eigenvectors such that the strain is reduced. Some sample calculations are presented for the system CuAuAg.
Fei Xue - One of the best experts on this subject based on the ideXlab platform.
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Strain phase separation: Formation of ferroelastic domain structures
Physical Review B, 2016Co-Authors: Fei Xue, Jinxing Zhang, Long-qing ChenAbstract:Phase decomposition is a well-known process leading to the formation of two-phase mixtures. Here we show that a strain imposed on a ferroelastic crystal promotes the formation of mixed phases and domains, i.e., strain phase separation with local strains determined by a Common Tangent Construction on the free energy versus strain curves. It is demonstrated that a domain structure can be understood using the concepts of domain/phase rule, lever rule, and coherent and incoherent strain phase separation, in a complete analogy to phase decomposition. The proposed strain phase separation model is validated using phase-field simulations and experimental observations of $\mathrm{PbTi}{\mathrm{O}}_{3}$ and $\mathrm{BiFe}{\mathrm{O}}_{3}$ thin films as examples. The proposed model provides a simple tool to guide and design domain structures of ferroelastic systems.
Gary R. Purdy - One of the best experts on this subject based on the ideXlab platform.
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Equilibrium and diffusion in coherent multilayers
Acta Materialia, 1996Co-Authors: Gary R. Purdy, Y.j.m. BrechetAbstract:Abstract A thermodynamic treatment is presented of isothermal phase equilibria and diffusion in coherent planar multilayers. For two-component systems, coherent two-phase equilibrium compositions can often be generated using the familiar procedure in which a line is constructed doubly Tangential to the coherent free energy functional(s). Only in special cases, however, are the phase equilibria so generated independent of the average composition (for unsupported multilayers) or the substrate effective composition (for multilayers coherently attached to a substrate). The Common Tangent Construction is extended to ternary solution systems, and conditions for which the coherent ternary equilibria are independent of the average or substrate compositions defined. The formal thermodynamic aspects of diffusion in binary and ternary solids are reviewed, and the expected effects of coherency strain on the diffusional homogenization process outlined. The diffusion formalism can often be extended to account for coherency strains simply by substituting the coherent free energy density for its incoherent counterpart. In ternary and higher order systems, it is always possible to choose an initial condition that is free of strain; it is not in general possible to maintain this strain-free condition during the course of diffusional homogenization. The general effect of strain energy on ternary diffusion is to rotate the diffusion eigenvectors such that the strain is reduced. Some sample calculations are presented for the system CuAuAg.
Jinxing Zhang - One of the best experts on this subject based on the ideXlab platform.
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Strain phase separation: Formation of ferroelastic domain structures
Physical Review B, 2016Co-Authors: Fei Xue, Jinxing Zhang, Long-qing ChenAbstract:Phase decomposition is a well-known process leading to the formation of two-phase mixtures. Here we show that a strain imposed on a ferroelastic crystal promotes the formation of mixed phases and domains, i.e., strain phase separation with local strains determined by a Common Tangent Construction on the free energy versus strain curves. It is demonstrated that a domain structure can be understood using the concepts of domain/phase rule, lever rule, and coherent and incoherent strain phase separation, in a complete analogy to phase decomposition. The proposed strain phase separation model is validated using phase-field simulations and experimental observations of $\mathrm{PbTi}{\mathrm{O}}_{3}$ and $\mathrm{BiFe}{\mathrm{O}}_{3}$ thin films as examples. The proposed model provides a simple tool to guide and design domain structures of ferroelastic systems.