Thermal expansion of LaAlO{sub 3} and (La,Sr)(Al,Ta)O{sub 3}, substrate materials for superconducting thin-film device applications
- Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393 (United States)
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802-5005 (United States)
- Commercial Crystal Laboratories, Inc., 4406 Arnold Avenue, Naples, Florida 33942 (United States)
- TRW, One Space Park, Redondo Beach, California 90278 (United States)
The thermal expansion for the perovskite (La,Sr)(Al,Ta)O{sub 3}, i.e., LSAT, grown from the formulation 0.29(LaAlO{sub 3}):0.35(Sr{sub 2}AlTaO{sub 6}), was determined by Rietveld refinement of neutron powder diffraction data over the temperature range of 15{endash}1200 K. In comparison to LaAlO{sub 3} the relative volume thermal expansion is the same, although the cell volume of LSAT is slightly larger. Site occupation refinement for LSAT gives a structural formula of (La{sub 0.29(5)}Sr{sub 0.71(5)}){sub A site}(Al{sub 0.65(1)}Ta{sub 0.35(1)}){sub B site}O{sub 3}. At and below 150 K, LSAT shows a small distortion from cubic symmetry. Unlike the cubic-to-rhombohedral transition (800 K) observed in LaAlO{sub 3}, the low temperature structural phase transition in LSAT appears to be cubic-to-tetragonal or cubic-to-orthorhombic. The rms displacement of the A site in LSAT is significantly larger than that for LaAlO{sub 3}, and about half of the difference can be accounted for by a static displacement component. {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 573943
- Journal Information:
- Journal of Applied Physics, Vol. 83, Issue 4; Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
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