High-pressure behaviour and atomic-scale deformation mechanisms in inyoite, CaB3O3(OH)5·4H2O

Abstract

The compressional behaviour of inyoite, ideally CaB3O3(OH)5•4H2O, has been studied by an insitu high-pressure single crystal X-ray experiment, at the ESRF large scale facility, up to 19.80(5) GPa. Inyoite undergoes a first-order phase transition to inyoite-II, bracketed between 8.25(5) and 8.86(5) GPa, with a large volume discontinuity (ΔV⁓7.5%). The structure of the high-pressure polymorph has not been solved due to a significant decrease in the number of Bragg reflections.The isothermal bulk modulus (KV0 = β −1 P0,T0, where βP0,T0 is the volume compressibility coefficient) of inyoite was found to be KV0 = 26.9(8) GPa, whereas in inyoite-II the KV0 value increases to 52(5) GPa. The increase of the bulk modulus is paired with a sharp decrease of the anisotropic compressibility, as shown by the magnitude of the Eulerian finite unit-strain ellipsoid with: ε1:ε2:ε3 = 3.5:2.1:1 in inyoite and ε1:ε2:ε3 =1.5:1.1:1 in inyoite-II. The P-induced deformation mechanisms controlling, at the atomic scale, the bulk compression of inyoite are here described on the basis of a series of structure refinements.

On the crystal-chemistry of meyerhofferite, CaB3O3(OH)5·H2O

“…In addition, these minerals release sodium, when dissolved into the paste, which can activate harmful reactions for the durability of Portland cement concretes. In the framework of a long-term project to select new B-bearing aggregates, as potential substituents of borax and ulexite in cement concretes, we have re-investigated the crystal chemistry, chemical stability and low/high-temperature and pressure behaviour of a series of natural borates: colemanite (CaB 3 O 4 (OH) 3 •H 2 O, Lotti et al 2017a,b;2019), kernite (Na 2 B 4 O 6 (OH) 2 •3H 2 O, Comboni et al 2020a;Gatta et al 2020), kurnakovite (MgB 3 O 3 (OH) 5 •5H 2 O, Gatta et al 2019;Pagliaro et al 2021) and inyoite (Ca 2 B 6 O 6 (OH) 10 •8H 2 O, Comboni et al 2021a). This study extends our investigation to meyerhofferite, which is a Na-free borate, ideally CaB 3 O 3 (OH) 5 •H 2 O (or Ca 2 B 6 O 6 (OH) 10 •2H 2 O), and contains up to 46.7 wt% B 2 O 3 .…”

High‐pressure behavior and phase transition of jadarite, a promising B and Li mineral commodity

“…On the other hand, above the phase transition, the +10% volume increase of the Li tetrahedron is coupled with a triplication of its 𝜎 2 (Table 2), reflecting a major increase in the Li tetrahedron deformation. Contrary to the other hydrous borates studied so far, the high-pressure phase transition of jadarite does not lead to an increase in the coordination of any boron site (e.g., 21,26,41,42 ). Furthermore, in other studies (e.g., meyerhofferite, colemanite, kernite, kurnakovite, ulexite, etc.…”

“…Contrary to the other hydrous borates studied so far, the high‐pressure phase transition of jadarite does not lead to an increase in the coordination of any boron site (e.g., 21,26,41,42 ). Furthermore, in other studies (e.g., meyerhofferite, colemanite, kernite, kurnakovite, ulexite, etc.…”

Atomic-scale deformation mechanisms at high-pressure in inderborite, CaMg[B3O3(OH)5]2(H2O)4⋅2H2O

“…In both the experiments, crystals did not recover after the phase transition. This was the most destructive phase transition observed in hydrated borates to date (e.g., Comboni et al, 2020bComboni et al, , 2022b, since the number of observed reflections was barely enough to properly index the diffraction pattern of the high-pressure polymorph, inderborite-II, which was found to be metrically monoclinic. The space group has not unambiguously determined.…”