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Low-temperature chemical routes to formation and IR properties of lanthanum sesquisulfide (La2S3) ceramics

Published online by Cambridge University Press:  31 January 2011

Prashant N. Kumta
Affiliation:
Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213-3890
Subhash H. Risbud
Affiliation:
Division of Materials Science and Engineering, The University of California, Davis, California 95616
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Abstract

Lanthanum sulfide (La2S3) exists in three different allotropic forms in the crystalline state. The low-temperature orthorhombic phase (α) transforms to the intermediate tetragonal phase (β) which further undergoes transformation to the high-temperature cubic phase (γ). The intermediate tetragonal phase (β) is an oxysulfide with possible use as a phosphor, and the cubic phase (γ) of La2S3 shows potential for application as a far IR (8–14 μm) window material. We report metal-organic synthesis routes for the preparation of the β- and γ-phases of La2S3 by processing modifications and choice of precursor chemistry. The alkoxide-derived precursors and the transformed sulfide powders were characterized for morphology, microstructure, and thermal stability. Phase evolution studies were also conducted, and the results are discussed in the context of formation of the β- and γ-phases. Results of densification, microstructure, and infrared transmission characteristics are also presented.

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Copyright
Copyright © Materials Research Society 1993

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