Crystal chemistry and temperature behavior of the natural hydrous borate colemanite, a mineral commodity of boron

Lotti, Paolo; Gatta, G. Diego; Demitri, Nicola; Guastella, Giorgio; Rizzato, Silvia; Ortenzi, Marco Aldo; Magrini, Fabrizio; Comboni, Davide; Guastoni, Alessandro; Fernández‐Díaz, M. T.

doi:10.1007/s00269-017-0929-7

Cited by 20 publications

(21 citation statements)

References 32 publications

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“…The same natural sample of massive and transparent colemanite, already investigated and described by [45,46], has been used for this study. The sample, provided by the Museum of Mineralogy of the University of Padua (Italy), comes from the borate deposits of the Bigadiç Mine (Balikesir Province, Marmara Region, Turkey [52]).…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…The chemical analysis has been performed by means of a multi-methodological approach, which surveyed more than 50 chemical species. The analytical protocol is described in [46], whereas the chemical composition, summarizing the major components, is reported in Table 1.…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…Full-profile fits were performed by the Rietveld method, using the GSAS [54] and EXPGUI [55] packages. The atomic coordinates reported in [46], for the same colemanite sample, were used as starting model. The background curve was modeled by a Chebyshev polynomial with 19 variable parameters, whereas the peak profiles were modelled using the pseudo-Voigt function of Thomson et al [56].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…The borate chains are linked along the c crystallographic direction by chains of corner-sharing Ca-coordination polyhedra (coordination number: 8, Figure 1), building up heteropolyhedral layers perpendicular to the b axis. Along that direction, the layers are interconnected by few Ca-O(H)-B bonds and an extensive network of H-bonds made by both the hydroxyl groups and the H2O molecules [46], resulting in weaker connections along the b axis that are responsible for the perfect (010) cleavage plane observed in colemanite crystals. On cooling, at temperatures between 0 and -12°C, depending on the amount of chemical impurities [50], colemanite undergoes a phase transition toward a ferroelectric polymorph, still monoclinic, but with space group P21 and a slightly displaced atomic arrangement [46,51].…”

Section: Crystal Structure Of Colemanitementioning

confidence: 99%

“…In this light, the scope of this study is to provide, by means of in situ differential scanning calorimetry, thermogravimetric and synchrotron X-ray diffraction analyses, a clearer picture of the behavior of colemanite at high temperature by: 1) providing a thorough characterization of the dehydration process and of its influence on the structural stability and 2) quantifying the volume thermal expansion coefficient at ambient conditions and at varying temperature. This study is part of a long-term project devoted to the characterization of the behavior of Bcontaining compounds at non-ambient conditions [40][41][42][43][44][45][46], which included: 1) the study of the high-pressure behavior of colemanite, reporting a P-induced reconstructive phase transition, characterized by the increased coordination of a fraction of B atoms from triangular to tetrahedral [45], and 2) the study of the low-T behavior of colemanite, with the transition to its ferroelectric polymorph [46].…”

Section: Introductionmentioning

confidence: 99%

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Thermal stability and high-temperature behavior of the natural borate colemanite: An aggregate in radiation-shielding concretes

Lotti

Comboni

Gigli

et al. 2019

Construction and Building Materials

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Colemanite is a natural borate that can be used as an aggregate in neutron-radiation shielding concretes. In this study, we report its thermal behavior, up to 500°C, by describing: 1) its dehydration mechanisms and 2) its thermo-elastic parameters. The thermal expansion of colemanite is significantly anisotropic. The refined volume thermal expansion coefficient at ambient conditions is: V0 = 4.50(10)10-5 K-1. The loss of structural H2O occurs at least from ~ 240 °C and at T > 325 °C, an irreversible amorphization occurs, followed by a complete dehydration. The potential implications on the use of colemanite as concrete-aggregate are discussed.

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Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Crystal Structure Of Colemanitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Thermal stability and high-temperature behavior of the natural borate colemanite: An aggregate in radiation-shielding concretes

Lotti

Comboni

Gigli

et al. 2019

Construction and Building Materials

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A single-crystal neutron diffraction study of wardite, NaAl3(PO4)2(OH)4·2H2O

et al. 2018

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The crystal structure and crystal chemistry of wardite, ideally NaAl 3 (PO 4 ) 2 (OH) 4 ·2H 2 O, was investigated by single-crystal neutron diffraction (data collected at 20 K) and electron microprobe analysis in wavelength-dispersive mode. The empirical formula of the sample used in this study is: (Na 0.91 Ca 0.01 ) Σ=0.92 (Al 2.97 Fe 3+ 0.05 Ti 0.01 ) Σ=3.03 (P 2.10 O 8 )(OH) 4 •1.74H 2 O. The neutron diffraction data confirm that the crystal structure wardite can be described with a tetragonal symmetry (space groupP4 1 2 1 2, a = b =7.0577(5) and c = 19.0559(5) Å at 20 K) and consists of sheets made by edge-sharing Na-polyhedra and Al-octahedra along with vertex-sharing Al-octahedra, parallel to (001), connected by P-tetrahedra and H-bonds to form a (001) layer-type structure, which well explains the pronounced {001} cleavage of the wardite crystals. The present data show that four crystallographically independent H sites occur into the structure of wardite, two belonging to a H 2 O molecule (i.e., H1-O6-H2) and two forming hydroxyl groups (i.e., O5-H3 and O7-H4). The location of the hydrogen atoms allow us to define the extensive network of H-bonds: the H-atoms belonging to the H 2 O molecule form strong H-bonds, whereas both the H-atoms belonging to the two independent hydroxyl groups form weak interactions with bifurcated bonding schemes. As shown by the root-mean-square components of the displacement ellipsoids, oxygen and hydrogen atoms have slightly larger anisotropic displacement parameters if compared to the other sites (populated by P, Al and Na). The maximum ratio of the max and min root-mean-square components of the displacement ellipsoids is observed for the protons of the hydroxyl groups, which experience bifurcated H-bonding schemes. A comparative analysis of the crystal structure of wardite and fluorowardite is also provided.

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

et al. 2020

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The high-pressure behaviour of meyerhofferite [ideally Ca2B6O6(OH)10ꞏ2(H2O), with a ~6.63 Å, b ~8.34 Å, c ~6.47 Å, α = 90.8°, β = 102°, γ=86.8°, Sp. Gr. P1 ], a B-bearing raw material (with B2O3  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., V~ 30 Å 3 ). The isothermal bulk modulus (KV0=  -1 P0,T0, where P0,T0 is the volume compressibility coefficient) of meyerhofferite was found to be KV0 =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.

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Crystal chemistry and temperature behavior of the natural hydrous borate colemanite, a mineral commodity of boron

Cited by 20 publications

References 32 publications

Thermal stability and high-temperature behavior of the natural borate colemanite: An aggregate in radiation-shielding concretes

Thermal stability and high-temperature behavior of the natural borate colemanite: An aggregate in radiation-shielding concretes

A single-crystal neutron diffraction study of wardite, NaAl3(PO4)2(OH)4·2H2O

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

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