Preparation and Characterization of a New Triclinic Compound Bi3.5V1.2O8.25 to Show the Known Phase Bi4V2O11 to Be Nonexistent as a Single Phase
✍ Scribed by Akiteru Watanabe
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 365 KB
- Volume
- 161
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
A new compound, Bi 3.5 V 1.2 O 8.25 (25.53 mol% V 2 O 5 ), has been found in the system Bi 2 O 3 +V 2 O 5 . It crystallizes in the triclinic symmetry with a ؍ 16.452(1) A > , b ؍ 16.886(1) A > , c ؍ 7.0914(7) A > , ؍ 91.330(8)3, ؍ 95.186(9)3, ؍ 96.031(9)3, and Z ؍ 10. The structure is considered a superstructure based on a pseudo-fcc subcell with a+5.5 A > , and the transformation matrix is ( 52 , 3 2 , 0)/(؊ 1,1,3)/( 1 2 ,؊1, 1 2 ). This compound yields low conductivity (10 ؊ 4 S cm ؊1 at 5003C); on heating, it decomposes into two unidenti5ed phases at 7903C, and melts at 8903C. Phase equilibrium studies between 25.53 and 50 mol% V 2 O 5 have shown that a mixture of Bi 3.5 V 1.2 O 8.25 and BiVO 4 is stable at least below 5503C and that the well-known phase Bi 4 V 2 O 11 does not exist as a pure phase. Thus, the reported 99 -Bi 4 V 2 O 11 -type:: solid solution is a metastable phase.