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Pseudocubic Perovskite-Like Lanthanide Gallate Crystals for Substrates

IP.com Disclosure Number: IPCOM000035106D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gallagher, WJ: AUTHOR [+4]

Abstract

Superconducting oxide materials with perovskite-like structures and composed of lanthanides, alkaline earths, bismuth, thallium, copper and other appropriate elements combined in the form of oxides have been refined further since the discovery of superconducting cuprates by K. A. Mueller and J. G. Bednorz (Z. Phys. B64, 189 (1986). The cuprates have only planar, not three-dimensional, superconductivity. Furthermore, epitaxial superconducting films on properly oriented perovskite-like single crystal substrates have higher limiting currents (important to device applications) compared to polycrystalline oxide superconductors in both film and bulk ceramic form.

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Pseudocubic Perovskite-Like Lanthanide Gallate Crystals for Substrates

Superconducting oxide materials with perovskite-like structures and composed of lanthanides, alkaline earths, bismuth, thallium, copper and other appropriate elements combined in the form of oxides have been refined further since the discovery of superconducting cuprates by K. A. Mueller and J. G. Bednorz (Z. Phys. B64, 189 (1986). The cuprates have only planar, not three- dimensional, superconductivity. Furthermore, epitaxial superconducting films on properly oriented perovskite-like single crystal substrates have higher limiting currents (important to device applications) compared to polycrystalline oxide superconductors in both film and bulk ceramic form. The presently preferred substrate for growing epitaxial films is the cubic perovskite SrTiO3, which has a nearly perfect lattice match for cuprates but is relatively soft and difficult to finish with a damage free flat surface. Also SrTiO3 has prohibitively high dielectric constants (e Z 200) for high frequency devices and it tends to react chemically with cuprates during film growth.

Large lanthanide gallate (LnGaO3) single crystals can be grown by the relatively simple Czochralski pulling method, and they can be processed into substrate wafers for epitaxial cuprate film growth. LaGaO3 has e = 25. Generally the lighter Ln gallates (where Ln is, e.g., La, Y, Nd and other rare earths singly or in solid solutions) have better lattice matches...