Browsing by Author "Smirnova, OA"

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    First observation of the reversible O3↔P2 phase transition: crystal structure of the quenched high-temperature phase Na0.74Ni0.58Sb0.42O2
    (Elsevier, 2006-06-15) Smirnova, OA; Avdeev, M; Nalbandyan, VB; Kharton, VV; Marques, FMB
    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.