Origin of Solid‐State Activated Sintering in Bi<sub>2</sub>O<sub>3</sub>‐Doped ZnO

Luo, Jian; Wang, Haifeng; Chiang, Yet‐Ming

doi:10.1111/j.1151-2916.1999.tb01853.x

Cited by 154 publications

(117 citation statements)

References 26 publications

(39 reference statements)

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“…If this problem were solved, engineers could confidently design interfaces with desired properties, e.g. increased toughness [2], tunable electrical conductivity [3] or enhanced sintering behaviour [4].…”

Section: Introductionmentioning

confidence: 99%

A genetic algorithm for predicting the structures of interfaces in multicomponent systems

et al. 2010

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Recent years have seen great advances in our ability to predict crystal structures from first principles. However, previous algorithms have focussed on the prediction of bulk crystal structures, where the global minimum is the target. Here, we present a general atomistic approach to simulate in multicomponent systems the structures and free energies of grain boundaries and heterophase interfaces with fixed stoichiometric and non-stoichiometric compositions. The approach combines a novel genetic algorithm using empirical interatomic potentials to explore the configurational phase space of boundaries, and thereafter refining structures and free energies with first principles electronic structure methods. We introduce a structural order parameter to bias the genetic algorithm search away from the global minimum (which would be bulk crystal), while not favouring any particular structure types, unless they lower the energy. We demonstrate the power and efficiency of the algorithm by considering nonstoichiometric grain boundaries in a ternary oxide, SrTiO 3 .

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Section: Introductionmentioning

confidence: 99%

A genetic algorithm for predicting the structures of interfaces in multicomponent systems

et al. 2010

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“…An important concept is that, despite the compressive force induced across particle contacts, enough of the liquid-forming material must remain adsorbed at the boundaries to provide the high boundary diffusion required to account for enhanced rates of densification via grain-boundary formation. 171,175 In Si 3 N 4 -based materials, boundaries with 1-2 nm thick, amorphous oxynitride films usually form between particles during liquid-phase sintering. 176 -178 Moreover, it has been shown that the boundary thickness is almost constant in a given material although it adjusts depending on the exact composition, 155,179 -181 implying that the thickness reflects some equilibrium condition.…”

Section: (7) Equilibrium Intergranular and Surficial Filmsmentioning

confidence: 99%

“…Moreover, the bismuthate film coexists with bulk solid or liquid phases, and it has been argued to be a true surface phase whose thickness and composition are determined by dispersion forces among other interactions. 215 These intergranular films have been implicated in subsolidus-activated sintering 217 as well as varistor behavior. 218 Recently, surface amorphous films of stable, nanometer thickness also have been identified in Bi 2 O 3 -ZnO (Fig.…”

Section: (C) Intergranular and Surficial Films In Znomentioning

confidence: 99%

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

French

2000

Journal of the American Ceramic Society

260

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The London dispersion forces, along with the Debye and Keesom forces, constitute the long-range van der Waals forces. London's and Hamaker's work on the point-to-point dispersion interaction and Lifshitz's development of the continuum theory of dispersion are the foundations of our understanding of dispersion forces. Dispersion forces are present for all materials and are intrinsically related to the optical properties and the underlying interband electronic structures of materials. The force law scaling constant of the dispersion force, known as the Hamaker constant, can be determined from spectral or parametric optical properties of materials, combined with knowledge of the configuration of the materials. With recent access to new experimental and ab initio tools for determination of optical properties of materials, dispersion force research has new opportunities for detailed studies. Opportunities include development of improved index approximations and parametric representations of the optical properties for estimation of Hamaker constants. Expanded databases of London dispersion spectra of materials will permit accurate estimation of both nonretarded and retarded dispersion forces in complex configurations. Development of solutions for generalized multilayer configurations of materials are needed for the treatment of more-complex problems, such as graded interfaces. Dispersion forces can play a critical role in materials applications. Typically, they are a component with other forces in a force balance, and it is this balance that dictates the resulting behavior. The ubiquitous nature of the London dispersion forces makes them a factor in a wide spectrum of problems; they have been in evidence since the pioneering work of Young and Laplace on wetting, contact angles, and surface energies. Additional applications include the interparticle forces that can be measured by direct techniques, such as atomic force microscopy. London dispersion forces are important in both adhesion and in sintering, where the detailed shape at the crack tip and at the sintering neck can be controlled by the dispersion forces. Dispersion forces have an important role in the properties of numerous ceramics that contain intergranular films, and here the opportunity exists for the development of an integrated understanding of intergranular films that encompasses dispersion forces, segregation, multilayer adsorption, and structure. The intrinsic length scale at which there is a transition from the continuum perspective (dispersion forces) to the atomistic perspective (encompassing interatomic bonds) is critical in many materials problems, and the relationship of dispersion forces and intergranular films may represent an important opportunity to probe this topic. Am. Ceram. Soc., 83 [9] 2117-46 (2000 Centennial FeatureThe London dispersion force is retarded at large separations, where the transit time of the electromagnetic interaction must be considered explicitly. Novel phenomena, such as equilibrium surficial films and bimodal wettin...

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“…10 Examples where the macroscopic properties of these materials depend critically on the grain boundary structures and the intergranular films include increased toughness, [11][12][13] reduced ionic conductivity, 9,[14][15][16][17] diminished creep resistance, 18,19 tunable electrical conductivity, 20,21 decreased thermal conductivity, 22 and enhanced sintering behavior. 23 The reason for this dominance is that interfaces inherently contain a concentration of defects and dopants far in excess of the equilibrium distribution in the bulk of the material. 24 This excess of defects results in the interface having a different atomic arrangement and consequently, different properties from the bulk.…”

Section: Introductionmentioning

confidence: 99%

Graded interface models for more accurate determination of van der Waals–London dispersion interactions across grain boundaries

et al. 2006

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Attractive van der Waals-London dispersion interactions between two half crystals arise from local physical property gradients within the interface layer separating the crystals. Hamaker coefficients and London dispersion energies were quantitatively determined for Σ5 and near-Σ13 grain boundaries in SrTiO 3 by analysis of spatially resolved valence electron energy-loss spectroscopy (VEELS) data. From the experimental data, local complex dielectric functions were determined, from which optical properties can be locally analyzed. Both local electronic structures and optical properties revealed gradients within the grain boundary cores of both investigated interfaces. The results show that even in the presence of atomically structured grain boundary cores with widths of less than 1 nm, optical properties have to be represented with gradual changes across the grain boundary structures to quantitatively reproduce accurate van der Waals-London dispersion interactions. London dispersion energies of the order of 10% of the apparent interface energies of SrTiO 3 were observed, demonstrating their significance in the grain boundary formation process. The application of different models to represent optical property gradients shows that long-range van der Waals-London dispersion interactions scale significantly with local, i.e., atomic length scale property variations. Attractive van der Waals-London dispersion interactions between two half crystals arise from local physical property gradients within the interface layer separating the crystals. Hamaker coefficients and London dispersion energies were quantitatively determined for ⌺5 and near-͚13 grain boundaries in SrTiO 3 by analysis of spatially resolved valence electron energy-loss spectroscopy ͑VEELS͒ data. From the experimental data, local complex dielectric functions were determined, from which optical properties can be locally analyzed. Both local electronic structures and optical properties revealed gradients within the grain boundary cores of both investigated interfaces. The results show that even in the presence of atomically structured grain boundary cores with widths of less than 1 nm, optical properties have to be represented with gradual changes across the grain boundary structures to quantitatively reproduce accurate van der Waals-London dispersion interactions. London dispersion energies of the order of 10% of the apparent interface energies of SrTiO 3 were observed, demonstrating their significance in the grain boundary formation process. The application of different models to represent optical property gradients shows that long-range van der Waals-London dispersion interactions scale significantly with local, i.e., atomic length scale property variations. Disciplines Engineering | Materials Science and Engineering Comments

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Origin of Solid‐State Activated Sintering in Bi₂O₃‐Doped ZnO

Cited by 154 publications

References 26 publications

A genetic algorithm for predicting the structures of interfaces in multicomponent systems

A genetic algorithm for predicting the structures of interfaces in multicomponent systems

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

Graded interface models for more accurate determination of van der Waals–London dispersion interactions across grain boundaries

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Origin of Solid‐State Activated Sintering in Bi2O3‐Doped ZnO

Cited by 154 publications

References 26 publications

A genetic algorithm for predicting the structures of interfaces in multicomponent systems

A genetic algorithm for predicting the structures of interfaces in multicomponent systems

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

Graded interface models for more accurate determination of van der Waals–London dispersion interactions across grain boundaries

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Origin of Solid‐State Activated Sintering in Bi₂O₃‐Doped ZnO