In-situ TEM crystallization of silicate-glass films on Al{sub 2}O{sub 3}

Journal Article · Fri Dec 19 04:00:00 EST 1997 · Acta Materialia

OSTI ID:585947

Mallamaci, M P; Carter, C B ^[1]; Bentley, J ^[2]

---

1. Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science
2. Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

Silicate-glass films were grown by pulsed-laser deposition on single-crystal, basal-plane Al{sub 2}O{sub 3} substrates which had been pre-thinned to electron transparency. Experiments were then performed at high temperature in the TEM, which allowed direct observation and video-recording of the crystallization process. The epitactic growth of pseudo-orthorhombic anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}) and grossular (Ca{sub 3}Al{sub 2}Si{sub 3}O{sub 12}) on the basal Al{sub 2}O{sub 3} surface was observed, emphasizing the role of the substrate as a ``seed`` for glass devitrification. The grossular crystals nucleated and grew at random on the substrate surface. In contrast, the anorthite crystals showed preferential nucleation at defect sites in the as-deposited glass film. Nucleation was followed by lateral growth along the substrate surface radiating away from the defect sites. Rotational variants for the silicate crystals were found in both cases, owing to the three-fold symmetry of the substrate. The simultaneous growth of these rotational variants on the substrate surface caused the formation of high-symmetry grain boundaries within the silicate film. In the anorthite film, these grain boundaries were often faceted parallel to low-index planes in one or both grains.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-92ER45465
• OSTI ID: 585947
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 1 Vol. 46; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CRYSTAL GROWTH
CRYSTALLIZATION
GLASS
GRAIN BOUNDARIES
SILICATES
TRANSMISSION ELECTRON MICROSCOPY