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Hydrothermal synthesis of new alkali silicates I. Potassium neodymium phases

Haile, S. M. and Wuensch, B. J. and Siegrist, T. and Laudise, R. A. (1993) Hydrothermal synthesis of new alkali silicates I. Potassium neodymium phases. Journal of Crystal Growth, 131 (3-4). pp. 352-372. ISSN 0022-0248. https://resolver.caltech.edu/CaltechAUTHORS:20131125-162532772

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Abstract

Hydrothermal techniques have been used to synthesize potassium neodymium silicates as potential new fast ion conductors (FICs). Alkali silicates are interesting both scientifically and technologically as FICs because of their typically open framework structures and the unique possibilities for crystal chemical tailoring. We describe here the growth conditions for eight phases, K_3NdSi_3O_8(OH)_2, K_3NdSi_7O_(17), K_5NdSi_9O_(22), K_8Nd_3Si_(12)O_(32)OH, K_3NdSi_6O_(15) (Bb * *), K_3NdSi_6O_(15) (Pbam), K_2NdSi_4O_(10)OH, and KNd_9(SiO_4)_6O_2 the first four of which have no known isomorphs. Syntheses has been carried out employing an aqueous solution of KOH, K_2CO_3, K_2B_4O_7, KF, or KHF_2 as the solvent, and either a glass of high silica content, 4K_2O-Nd_2O_3-17SiO_2, or a mixture of Nd_2O_3, vitreous SiO_2 and K_2CO_3 as the precursor material. Pressures, temperatures, and solution molarities utilized ranged from 0.3 to 1.4 kbar, from 350 to 600 ° C, and from 0 to 10 M, respectively. Experiments, performed both isothermally and under the influence of a temperature gradient, proceeded for 5 to 20 days. Phases were identified using electron microprobe composition measurements and X-ray single-crystal and powder diffraction methods. Most phases were produced under well-defined conditions and synthesis was characterized by a tendency to crystallize compounds of low silica content and hence low connectivity of the SiO_4 tetrahedra in the crystal structure at high molarities, high temperatures, and, to some extent, high pressures. Of the eight phases listed, six were obtained as crystals large enough for X-ray structure determination and conductivity measurements along at least one crystallographic axis.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0022-0248(93)90185-YDOIArticle
http://www.sciencedirect.com/science/article/pii/002202489390185YPublisherArticle
ORCID:
AuthorORCID
Haile, S. M.0000-0002-5293-6252
Additional Information:Copyright © 1993 Published by Elsevier. Received 20 November 1992. Accepted 23 March 1993. Many thanks are due to Anthony J. Caporaso (AT&T Bell Laboratories) for instruction and guidance in the hydrothermal technique and Bill Grodkiewicz (AT&T Bell Laboratories) for aid in glass preparation. We are indebted to Dr. Robert Opila (AT&T Bell Laboratories) an Mike Jercinovic (Massachusetts Institute of Technology) for assistance with EDX and WDX composition determinations, respectively. Dr. Bruce Foxman (Brandeis University) and Dr. Karl Peters (Max-Planck Institute für Festkörperforschung) have kindly provided single crystal intensity data for some phases. The authors are also grateful to Dr. O. V. Dimitrova (Moscow University) for helpful discussions. S. Haile acknowledges the AT&T Cooperative Research Fellowship Program for generous financial support.
Funders:
Funding AgencyGrant Number
AT&T Cooperative Research FellowshipUNSPECIFIED
Issue or Number:3-4
Record Number:CaltechAUTHORS:20131125-162532772
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131125-162532772
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42724
Collection:CaltechAUTHORS
Deposited By: Jonathan Gross
Deposited On:02 Dec 2013 21:40
Last Modified:03 Oct 2019 06:01

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