First observation of the reversible O3↔P2 phase transition: crystal structure of the quenched high-temperature phase Na0.74Ni0.58Sb0.42O2

Smirnova, OA; Avdeev, M; Nalbandyan, VB; Kharton, VV; Marques, FMB

First observation of the reversible O3↔P2 phase transition: crystal structure of the quenched high-temperature phase Na0.74Ni0.58Sb0.42O2

Date

2006-06-15

Authors

Publisher

Elsevier

Abstract

According to thermal expansion data, O3-type phase NaxNi(1+x)/3Sb(2−x)/3O2 (x ≈ 0.8) undergoes at ca. 1270 K a reversible transition to a less dense form. The high-temperature phase quenched to liquid nitrogen belongs to P2 type, space group P63/mmc (no. 194), a = 3.0123 Å(2), c = 11.2264 Å(7) for x ≈ 0.74 at 298 K. The stabilisation of P2 versus O3-type structure at high temperatures seems to be due to alkali distribution over greater number of sites thus increasing entropy and decreasing Na+–Na+ repulsion. © 2005 Elsevier Ltd.

Keywords

Thermal expansion, Crystal structure, X-ray diffraction, Phase transformations, Nitrogen, Entropy

Citation

Smirnova, O. A., Avdeev, M., Nalbandyan, V. B., Kharton, V. V., & Marques, F. M. B. (2006). First observation of the reversible O3↔P2 phase transition: crystal structure of the quenched high-temperature phase Na0.74Ni0.58Sb0.42O2. Materials Research Bulletin, 41(6), 1056-1062. doi:10.1016/j.materresbull.2005.11.014