Data di Pubblicazione:
2020
Citazione:
High-pressure behavior and phase stability of Na2B4O6(OH)2·3H2O (kernite) / D. Comboni, F. Pagliaro, G.D. Gatta, P. Lotti, S. Milani, M. Merlini, T. Battiston, K. Glazyrin, H. Liermann. - In: JOURNAL OF THE AMERICAN CERAMIC SOCIETY. - ISSN 0002-7820. - 103:9(2020 Sep), pp. 5291-5301.
Abstract:
The high-pressure behavior of kernite [ideally Na2B4O6(OH)2·3H2O, a ~ 7.02 Å,
b ~ 9.16 Å, c ~ 15.68 Å, β = 108.9°, Sp Gr P21/c, at ambient conditions], an important
B-bearing raw material (with B2O3 ≈ 51 wt%) and a potential B-rich aggregate
in radiation shielding materials, has been studied by single-crystal synchrotron X-ray
diffraction up to 14.6 GPa. Kernite undergoes an iso-symmetric phase transition at
1.6-2.0 GPa (to kernite-II). Between 6.6-7.5 GPa, kernite undergoes a second phase
transition, possibly iso-symmetric in character (to kernite-III). The crystal structure
of kernite-II was solved and refined. The isothermal bulk modulus (KV0 = β-1
P0,T0, where βP0,T0 is the volume compressibility coefficient) of the ambient-pressure polymorph
of kernite was found to be KV0 = 29(1) GPa and a marked anisotropic compressional
pattern, with K(a)0: K(b)0: K(c)0~1:3:1.5., was observed. In kernite-II, the
KV0 increases to 43.3(9) GPa and the anisotropic compressional pattern increases
pronouncedly. The mechanisms, at the atomic scale, which govern the structure deformation,
have been described.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
borates; high-pressure; phase-transitions; single crystals; X-ray methods
Elenco autori:
D. Comboni, F. Pagliaro, G.D. Gatta, P. Lotti, S. Milani, M. Merlini, T. Battiston, K. Glazyrin, H. Liermann
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