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Abstract This study investigates the grain boundary energy dependence on segregated dopants in nanocrystalline zinc aluminate ceramics. Atomistic simulations of Σ3 and Σ9 grain boundaries showed that trivalent ions of varying ionic radii [Sc3+(74.5 pm), In3+(80.0 pm), Y3+(90.0 pm), and Nd3+(98.3 pm)] have a tendency to segregate to both interfaces, with Y3+presenting the highest segregation potentials. The connection between segregation and the reduction of interfacial energies was explored by measuring the grain boundary energy on nanoceramics fabricated via high‐pressure spark plasma sintering (HP‐SPS) using differential scanning calorimetry (DSC). The results revealed that Y3+doping at 0.5 mol% reduces the grain boundary energy in zinc aluminate nanoceramics from 1.1–1.3 J/m2to 0.6–0.8 J/m2; the range correlates with the observed size dependence of the excess energy, with higher values observed for the smaller grain sizes (∼17 nm). The noted decrease in interfacial energies for doped samples suggests it is indeed possible to alter the stability of zinc aluminate grain boundaries via dopant segregation.
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Thermodynamic and kinetic analyses of sintering in Al‐doped Y 2 O 3 nanoparticles
Abstract This work investigates the effects of doping on both the thermodynamics and kinetics of sintering in aluminum‐doped yttrium oxide nanoparticles (Al‐doped Y2O3), with the objective of delineating their interdependent effects at different stages of the process. Direct measurements of surface and grain boundary energies using differential scanning calorimetry showed that Al‐doping decreases both interfacial energies, leading to an increase in dihedral angle (from 152.7 ± 5.6° to 165.8 ± 5.5°) and, therefore, sintering stress. Densification and grain growth analyses showed that despite this increase in sintering stress, the onset of sintering is delayed for the Al‐doped samples, demonstrating that a large dihedral angle is a necessary but not sufficient condition for densification. The measurements of activation energies for densification and grain growth point out that Al suppresses grain boundary mobility by increasing the activation energy from 400 to 448 kJ/mol, hindering densification at the intermediate stages of sintering. At temperatures above 1150℃, grain growth is activated in the Al‐doped samples, which rapidly releases the accumulated sintering stress and exhibits a higher densification rate than in undoped Y2O3. This study demonstrates a complex interconnectivity between the thermodynamics and kinetics at different temperature ranges of sintering and reinforces the need for a comprehensive description for proper design of sintering aids.
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- Award ID(s):
- 2015650
- PAR ID:
- 10367541
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 105
- Issue:
- 1
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 147-158
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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