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Title: Structural Effects of Lanthanide Dopants on Alumina

Abstract

Lanthanide (Ln 3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1338998
Resource Type:
Journal Article
Resource Relation:
Journal Name: Scientific Reports; Journal Volume: 7; Journal Issue: 01, 2017
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Patel, Ketan, Blair, Victoria, Douglas, Justin, Dai, Qilin, Liu, Yaohua, Ren, Shenqiang, and Brennan, Raymond. Structural Effects of Lanthanide Dopants on Alumina. United States: N. p., 2017. Web. doi:10.1038/srep39946.
Patel, Ketan, Blair, Victoria, Douglas, Justin, Dai, Qilin, Liu, Yaohua, Ren, Shenqiang, & Brennan, Raymond. Structural Effects of Lanthanide Dopants on Alumina. United States. doi:10.1038/srep39946.
Patel, Ketan, Blair, Victoria, Douglas, Justin, Dai, Qilin, Liu, Yaohua, Ren, Shenqiang, and Brennan, Raymond. Fri . "Structural Effects of Lanthanide Dopants on Alumina". United States. doi:10.1038/srep39946.
@article{osti_1338998,
title = {Structural Effects of Lanthanide Dopants on Alumina},
author = {Patel, Ketan and Blair, Victoria and Douglas, Justin and Dai, Qilin and Liu, Yaohua and Ren, Shenqiang and Brennan, Raymond},
abstractNote = {Lanthanide (Ln3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.},
doi = {10.1038/srep39946},
journal = {Scientific Reports},
number = 01, 2017,
volume = 7,
place = {United States},
year = {Fri Jan 06 00:00:00 EST 2017},
month = {Fri Jan 06 00:00:00 EST 2017}
}
  • Lanthanide (Ln 3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO 3, Ln 2O 3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. In addition, the delay in phase transition (θ → α),more » and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. Lastly, this study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.« less
  • Starting from the atomic structure of silicon quantum dots (QDs), and utilizing ab initio electronic structure calculations within the Förster resonance energy transfer (FRET) treatment, a model has been developed to characterize electronic excitation energy transfer between QDs. Electronic energy transfer rates, K{sub EET}, between selected identical pairs of crystalline silicon quantum dots systems, either bare, doped with Al or P, or adsorbed with Ag and Ag{sub 3}, have been calculated and analyzed to extend previous work on light absorption by QDs. The effects of their size and relative orientation on energy transfer rates for each system have also beenmore » considered. Using time-dependent density functional theory and the hybrid functional HSE06, the FRET treatment was employed to model electronic energy transfer rates within the dipole-dipole interaction approximation. Calculations with adsorbed Ag show that: (a) addition of Ag increases rates up to 100 times, (b) addition of Ag{sub 3} increases rates up to 1000 times, (c) collinear alignment of permanent dipoles increases transfer rates by an order of magnitude compared to parallel orientation, and (d) smaller QD-size increases transfer due to greater electronic orbitals overlap. Calculations with dopants show that: (a) p-type and n-type dopants enhance energy transfer up to two orders of magnitude, (b) surface-doping with P and center-doping with Al show the greatest rates, and (c) K{sub EET} is largest for collinear permanent dipoles when the dopant is on the outer surface and for parallel permanent dipoles when the dopant is inside the QD.« less
  • To achieve low-temperature superplasticity in alumina, the authors have introduced charge-compensating dopants, Ti{sup 4+} and Mn{sup 2+}, which jointly have a high solubility and significantly enhance the diffusion and deformation processes during sintering and forming. Zirconia as a second-phase pinning agent has also been incorporated to impart microstructural stability against static and dynamic grain growth. The superplastic alumina obtained can be shape-formed under biaxial tension to 100% engineering strain at temperatures below 1,300 C. Deformation characteristics of this alumina at temperatures from 1,200 to 1,400 C and at strain rates from 4 {times} 10{sup {minus}6} to 3 {times} 10{sup {minus}3}/smore » are described. The origin of enhanced kinetics is attributed to the formation and dissociation of dopant-defect complexes.« less
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