Structure and Crystal Chemistry as a Function of Composition across the Wide Range Nonstoichiometric (1−ε)ZrO2·εSmO1.5, 0.38<ε<0.55, Oxide Pyrochlore System
✍ Scribed by Yasunori Tabira; Ray L. Withers
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 397 KB
- Volume
- 148
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The extent of the pyrochlore solid solution 5eld (at 15003C) in the (1؊ )ZrO 2 ' SmO 1.5 system has been determined as running from 38.5 to 55 mol% SmO 1.5 . Subtle changes in crystal structure have been investigated as a function of composition across this solid solution 5eld using a wide-angle convergent beam electron di4raction technique. Systematic changes in the one unknown oxygen atom fractional coordinate x are found as a function of composition and investigated from a crystal chemical point of view using the bond length + bond valence approach. The parameter x is found to be &0.352 for ؍ 0.40 and 0.348 for ؍ 0.45 and 0.55. Both values of x are signi5cantly larger than the value (x ؍ 0.342) found for the stoichiometric 50 mol% SmO 1.5 specimen by the same technique. The increased x value found for nonstoichiometric compositions on either side of the ideal pyrochlore composition ( ؍ 0.5) is consistent with a systematic shift toward the average value for this parameter in the so-called 99defect 6uorite:: structure (x ؍ 0.375), the phase 5eld for which appears on either side of the relevant pyrochlore solid solution 5eld.