Sol-gel-derived single-crystal alumina coatings with vermicular structure

Sreya Dutta, Taek Bo Kim, Timothy Krentz, Richard P. Vinci, Helen M. Chan

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Alumina sols were spin-coated on {0001} (c-plane) sapphire substrates. Heat treatment in air at temperatures varying between 1100° and 1400°C resulted in epitaxial conversion of the coating to α-alumina. Seeded single-crystal conversion could be achieved at temperatures as low as 1025°C at longer annealing times (18 h). The converted coatings were crack free, and exhibited a porous, vermicular microstructure that was attributed to the negative volume change during the γ to α alumina phase change, coupled with the volume constraint of the underlying sapphire substrate. Isolated regions of the coating that had delaminated from the substrate did not convert to {0001} sapphire, but instead remained polycrystalline after heat treatment. Single-crystal islands that were not c-plane oriented were occasionally observed at shorter times. It is suggested that such regions resulted from the random nucleation of α-grains with a more rapid growth rate in the direction perpendicular to the substrate. The epitaxial conversion of alumina sol-gel coatings provides a potentially convenient method for generating patterned, single-crystal ceramic substrates for a variety of applications.

Original languageEnglish (US)
Pages (from-to)340-343
Number of pages4
JournalJournal of the American Ceramic Society
Volume94
Issue number2
DOIs
StatePublished - Feb 1 2011

Fingerprint

Aluminum Oxide
aluminum oxide
Sol-gels
coating
sapphire
Alumina
gel
Single crystals
crystal
substrate
Coatings
Sapphire
Substrates
Heat treatment
volume change
annealing
Sols
ceramics
nucleation
microstructure

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

Cite this

Sol-gel-derived single-crystal alumina coatings with vermicular structure. / Dutta, Sreya; Kim, Taek Bo; Krentz, Timothy; Vinci, Richard P.; Chan, Helen M.

In: Journal of the American Ceramic Society, Vol. 94, No. 2, 01.02.2011, p. 340-343.

Research output: Contribution to journalArticle

Dutta, Sreya ; Kim, Taek Bo ; Krentz, Timothy ; Vinci, Richard P. ; Chan, Helen M. / Sol-gel-derived single-crystal alumina coatings with vermicular structure. In: Journal of the American Ceramic Society. 2011 ; Vol. 94, No. 2. pp. 340-343.
@article{160af5a9a01b47db8ae43e702f96a4c0,
title = "Sol-gel-derived single-crystal alumina coatings with vermicular structure",
abstract = "Alumina sols were spin-coated on {0001} (c-plane) sapphire substrates. Heat treatment in air at temperatures varying between 1100° and 1400°C resulted in epitaxial conversion of the coating to α-alumina. Seeded single-crystal conversion could be achieved at temperatures as low as 1025°C at longer annealing times (18 h). The converted coatings were crack free, and exhibited a porous, vermicular microstructure that was attributed to the negative volume change during the γ to α alumina phase change, coupled with the volume constraint of the underlying sapphire substrate. Isolated regions of the coating that had delaminated from the substrate did not convert to {0001} sapphire, but instead remained polycrystalline after heat treatment. Single-crystal islands that were not c-plane oriented were occasionally observed at shorter times. It is suggested that such regions resulted from the random nucleation of α-grains with a more rapid growth rate in the direction perpendicular to the substrate. The epitaxial conversion of alumina sol-gel coatings provides a potentially convenient method for generating patterned, single-crystal ceramic substrates for a variety of applications.",
author = "Sreya Dutta and Kim, {Taek Bo} and Timothy Krentz and Vinci, {Richard P.} and Chan, {Helen M.}",
year = "2011",
month = "2",
day = "1",
doi = "10.1111/j.1551-2916.2010.04307.x",
language = "English (US)",
volume = "94",
pages = "340--343",
journal = "Journal of the American Ceramic Society",
issn = "0002-7820",
publisher = "Wiley-Blackwell",
number = "2",

}

TY - JOUR

T1 - Sol-gel-derived single-crystal alumina coatings with vermicular structure

AU - Dutta, Sreya

AU - Kim, Taek Bo

AU - Krentz, Timothy

AU - Vinci, Richard P.

AU - Chan, Helen M.

PY - 2011/2/1

Y1 - 2011/2/1

N2 - Alumina sols were spin-coated on {0001} (c-plane) sapphire substrates. Heat treatment in air at temperatures varying between 1100° and 1400°C resulted in epitaxial conversion of the coating to α-alumina. Seeded single-crystal conversion could be achieved at temperatures as low as 1025°C at longer annealing times (18 h). The converted coatings were crack free, and exhibited a porous, vermicular microstructure that was attributed to the negative volume change during the γ to α alumina phase change, coupled with the volume constraint of the underlying sapphire substrate. Isolated regions of the coating that had delaminated from the substrate did not convert to {0001} sapphire, but instead remained polycrystalline after heat treatment. Single-crystal islands that were not c-plane oriented were occasionally observed at shorter times. It is suggested that such regions resulted from the random nucleation of α-grains with a more rapid growth rate in the direction perpendicular to the substrate. The epitaxial conversion of alumina sol-gel coatings provides a potentially convenient method for generating patterned, single-crystal ceramic substrates for a variety of applications.

AB - Alumina sols were spin-coated on {0001} (c-plane) sapphire substrates. Heat treatment in air at temperatures varying between 1100° and 1400°C resulted in epitaxial conversion of the coating to α-alumina. Seeded single-crystal conversion could be achieved at temperatures as low as 1025°C at longer annealing times (18 h). The converted coatings were crack free, and exhibited a porous, vermicular microstructure that was attributed to the negative volume change during the γ to α alumina phase change, coupled with the volume constraint of the underlying sapphire substrate. Isolated regions of the coating that had delaminated from the substrate did not convert to {0001} sapphire, but instead remained polycrystalline after heat treatment. Single-crystal islands that were not c-plane oriented were occasionally observed at shorter times. It is suggested that such regions resulted from the random nucleation of α-grains with a more rapid growth rate in the direction perpendicular to the substrate. The epitaxial conversion of alumina sol-gel coatings provides a potentially convenient method for generating patterned, single-crystal ceramic substrates for a variety of applications.

UR - http://www.scopus.com/inward/record.url?scp=79751522574&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79751522574&partnerID=8YFLogxK

U2 - 10.1111/j.1551-2916.2010.04307.x

DO - 10.1111/j.1551-2916.2010.04307.x

M3 - Article

AN - SCOPUS:79751522574

VL - 94

SP - 340

EP - 343

JO - Journal of the American Ceramic Society

JF - Journal of the American Ceramic Society

SN - 0002-7820

IS - 2

ER -