Details

Autor(en) / Beteiligte

• Comboni, Davide
• Pagliaro, Francesco
• Gatta, G. Diego
• Lotti, Paolo
• Battiston, Tommaso
• Garbarino, Gaston
• Hanfland, Michael

Titel

High-pressure behaviour and phase stability of Ca2B6O6(OH)10·2(H2O) (meyerhofferite)

Ist Teil von

• Physics and chemistry of minerals, 2020-11, Vol.47 (11), Article 50

Ort / Verlag

Berlin/Heidelberg: Springer Berlin Heidelberg

Erscheinungsjahr

2020

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The high-pressure behaviour of meyerhofferite [ideally Ca 2 B 6 O 6 (OH) 10 ·2(H 2 O), with a  ~ 6.63 Å, b  ~ 8.34 Å, c  ~ 6.47 Å, α = 90.8°, β  = 102°, γ = 86.8°, Sp. Gr. P 1 ¯ ], a B-bearing raw material (with B 2 O 3 ≈ 46 wt%) and a potential B-rich aggregate, has been studied by single-crystal synchrotron X-ray diffraction up to 9 GPa, under hydrostatic conditions. Meyerhofferite undergoes a first-order phase transition to meyerhofferite-II, likely iso-symmetric, bracketed between 3.05 and 3.48 GPa, with a spectacular unit-cell volume discontinuity ( i.e ., Δ V  ~ 30 Å 3 ). The isothermal bulk modulus ( K V0  = β −1 P0,T0 , where β P0,T0 is the volume compressibility coefficient) of meyerhofferite, was found to be K V0  = 31.6(5) GPa, and a marked anisotropic compressional pattern, with K ( a) 0 : K ( b) 0 : K ( c) 0  ~ 1.5:1:3, was observed. The bulk modulus of meyerhofferite-II increases to 55(2) GPa and, differently to the majority of the borates studied at high pressure so far, the anisotropic compressional pattern of meyerhofferite decreases markedly in the high-pressure form. The P -induced deformation mechanisms controlling, at the atomic scale, the bulk compression of meyerhofferite are here described. Considerations about the use of meyerhofferite as a potential B-based aggregate in concretes, mortars or resins, are provided.