Electrical conductivity of MOXO{sub 4} (M=V, Nb; X=P, As) compounds intercalated with H{sub 2}O and H{sub 3}XO{sub 4}
- Joint Laboratory of Solid State Chemistry of Institute of Macromolecular Chemistry Acad. Sci. Czech Republic and University of Pardubice, Studentska 84, 532 10 Pardubice (Czech Republic)
- Dipartimento di Chimica, Centro di Eccellenza Materiali Innovativi Nanostrutturati, Universita di Perugia, via Elce di Sotto 8, 06123 Perugia (Italy)
Layered compounds with the general formula MOXO{sub 4}.yH{sub 2}O (M=V, Nb; X=P, As) were prepared. The content of water y was controlled by keeping the samples in an atmosphere with various relative humidities (RH). Depending on RH, the formation of several hydrates of niobyl phosphate and arsenate was observed and their basal spacings (d) were determined, namely, NbOPO{sub 4}.H{sub 2}O, d=6.4A, at 11% RH and lower, NbOPO{sub 4}.2H{sub 2}O, d=7.0A, at 22-33% RH, NbOPO{sub 4}.3H{sub 2}O, d=7.8A, at 43-84% RH, and NbOPO{sub 4}.5H{sub 2}O, d=8.0A, at 92% RH and above; NbOAsO{sub 4}.H{sub 2}O, d=6.2A, at 0-16% RH and NbOAsO{sub 4}.3H{sub 2}O, d=7.9A at 33% RH and above. As follows from ac and dc conductivity data, NbOXO{sub 4}.yH{sub 2}O compounds are practically pure protonic conductors, whereas VOXO{sub 4}.yH{sub 2}O compounds are mixed protonic-electronic conductors and the protonic component increases with y. Two intercalates of MOXO{sub 4}.yH{sub 2}O with inorganic acids were prepared. A new intercalate of H{sub 3}AsO{sub 4} into VOAsO{sub 4}.yH{sub 2}O with the formula VOAsO{sub 4}.0.5H{sub 3}AsO{sub 4}.yH{sub 2}O (y=0.5-0.8) has the cell parameters a=6.37 and c=8.81-9.13A at 0-22% RH. Above 22% RH, the intercalate decomposes and the parent VOAsO{sub 4}.yH{sub 2}O with H{sub 3}AsO{sub 4} adsorbed on the surface is formed. Another intercalate with formula NbOPO{sub 4}.H{sub 3}PO{sub 4}.yH{sub 2}O (y=2-4 at 0-75% RH) has the cell parameters a=6.43 and c=9.56-9.70A at RH from 0% to 5% and a=6.48 and c=11.2A at RH from 33% to 75%. Both intercalates are more conductive than their MOXO{sub 4}.yH{sub 2}O hosts and their conductivity increases with increasing RH of the surrounding atmosphere. Like NbOPO{sub 4}.yH{sub 2}O, also NbOPO{sub 4}.H{sub 3}PO{sub 4}.yH{sub 2}O can be considered pure proton conductor and its conductivity at 20 deg. C reaches 5x10{sup -3}Scm{sup -1} for y=4.
- OSTI ID:
- 20725962
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 6; Other Information: DOI: 10.1016/j.jssc.2005.03.016; PII: S0022-4596(05)00108-8; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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