High-pressure structural configuration and phase transition in celsian, BaAl2Si2O8

Curetti, Nadia; Benna, Piera; Bruno, E.

doi:10.1007/s00269-016-0847-0

Cited by 9 publications

(9 citation statements)

References 30 publications

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“…The bulk modulus of strontium feldspar is 90 GPa up to 3.7 GPa, with a volume softening for P > 4.2 GPa. In a preliminary study on HP behavior of barium feldspar, Curetti et al (2011a) observed a similar phase transition between 5.5 and 5.9 GPa in natural celsian.…”

mentioning

confidence: 67%

“…A similar trend in b angle was observed by Tribaudino et al (1999) in lead feldspar up to 7.1 GPa in a HP powder diffraction study. Considering all the other feldspars till now examined at HP, the b angle decreases in anorthite, celsian (Curetti et al 2011a), SrFsp 100 , and An 20 SrFsp 80 feldspars, while it increases in alkali feldspars with a plateau effect (Allan and Angel 1997;Nestola et al 2008).…”

Section: Lattice Deformationmentioning

confidence: 92%

“…Indeed, the pressure of the transition seems to increase with the decrease of the mean ionic radius of the M cation (Ba, Sr, Ca). The I2/c-P2 1 /c transition occurs in barium feldspar between 5.5 and 5.9 GPa (Curetti et al 2011a), while in strontium feldspar (with Sr 2+ cation smaller than Ba 2+ ) it occurs at about 6.6 GPa (Pandolfo et al 2011). The substitution of 20% of CaAl 2 Si 2 O 8 component into the strontium feldspar structure (with a decrease in the mean ionic radius) causes an increase of the transition pressure: in the Ca 0.2 Sr 0.8 Al 2 Si 2 O 8 feldspar the I2/c-P2 1 /c transition occurs at about 7.3 GPa (Nestola et al 2004).…”

Section: Hp Phase Transition: a Comparison With Alkaline-earth Feldsparsmentioning

confidence: 99%

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High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

Curetti

Benna

Bruno

2015

American Mineralogist

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In situ high-pressure X-ray diffraction study was performed on synthetic lead feldspar with composition PbAl 2 Si 2 O 8 (PbFsp). The crystals were synthesized from the melt and thermally treated at T = 1150 °C for 12 h and at T = 1000 °C for 70 h. At room condition the unit-cell parameters are a = 8.3936(4), b = 13.0498 (7), c = 14.3258(8) Å, b = 115.281(6)°, V = 1418.9(1) Å 3 ; space group: I2/c; Q od = 0.7.A single-crystal of lead feldspar was loaded in an ETH-type diamond-anvil cell and unit-cell parameters were measured at 26 different pressures up to 8.4 GPa at room T. The evolution with P of the unit-cell parameters and volume shows a strong discontinuity between 7.7 and 8.2 GPa indicating a first-order phase transition. The discontinuous character of the transition is especially noticeable in the behavior of the b angle, which decreases from 114.83° to 114.03°, and in the b parameter, which reduces from 12.746 to 12.567 Å.In the P range 0.0001-7.72 GPa, the trend shown by the axial compressibilityis similar to that observed in the previous HP powder diffraction study, performed on lead feldspar using high-brilliance synchrotron radiation up to 7.1 GPa.In the P range 0.0001-4.27 GPa at room T, the P-V data of the I2/c lead feldspar were fitted with a second-order Birch-Murnaghan EoS. The parameters obtained are: V 0 = 1422.2(1) Å 3 and K T0 = 76.4(9) GPa. At P > 4.27 GPa, the volume values deflect from the BM2 curve and show a volume softening, precursor of the reported HP phase transition. A volume softening was recently observed in strontium feldspar (SrFsp) above 4.2 GPa.A second crystal of PbFsp was loaded in the DAC cell and in situ high-pressure X-ray diffraction intensities were measured at P = 0.0001, 2.4, 3.1, 5.4, 6.0, 7.2, 8.4, and 9.7 GPa. The appearance of c and d-type reflections at 8.4 GPa, the analysis of the systematic absence and the structural refinements indicate the HP first-order transformation as an I2/c-P2 1 /c phase transition. Structural results show that the main variations with compression in lead feldspar are in Pb-O bond lengths and in T-O-T bond angles, while T-O distances and O-T-O angles do not change meaningfully, indicating that the Si,Al tetrahedra behave with pressure as a rigid body. Changes observed in the compressional behavior of the structure between 3 and 5 GPa could explain the softening observed at P > 4 GPa in the volume compressibility.The results obtained in the present work allow comparing the pressures of the HP I2/c-P2 1 /c phase transition occurring in lead feldspar with those observed in alkaline-earth feldspars.

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mentioning

confidence: 67%

Section: Lattice Deformationmentioning

confidence: 92%

Section: Hp Phase Transition: a Comparison With Alkaline-earth Feldsparsmentioning

confidence: 99%

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High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

Curetti

Benna

Bruno

2015

American Mineralogist

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“…The high-pressure behavior of celsian was studied recently by Curetti et al . 37 , who discovered a new P 2 1 / c high-pressure modification existing above 5.7 GPa.…”

Section: Introductionmentioning

confidence: 99%

“…Due to their high geological relevance and various technological applications, numerous X-ray diffraction studies at non-ambient conditions (high temperature (HT) and/or pressure (HP)) have been performed with detailed studies focused on orthoclase, sanidine, microcline, albite, and anorthite 57–72 . In feldspar-related minerals and inorganic compounds with divalent cations such as celsian, BaAl 2 Si 2 O 8 37 , PbAl 2 Si 2 O 8 64 , SrAl 2 Si 2 O 8 73,74 , and solid solutions between these compounds 75–77 , several phase transitions were found upon compression. However, all the reported phase transitions occur with a symmetry change but without reconstructive transformations in the aluminosilicate frameworks.…”

Section: Introductionmentioning

confidence: 99%

High pressure phase transitions of paracelsian BaAl2Si2O8

Gorelova

Pakhomova

Krivovichev

et al. 2019

Sci Rep

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Three new polymorphs of aluminosilicate paracelsian, BaAl 2 Si 2 O 8 , have been discovered using synchrotron-based in situ high-pressure single crystal X-ray diffraction. The first isosymmetric phase transition (from paracelsian-I to paracelsian-II) occurs between 3 and 6 GPa. The phase transition is associated with the formation of pentacoordinated Al 3+ and Si 4+ ions, which occurs in a stepwise fashion by sequential formation of Al-O and Si-O bonds additional to those in AlO 4 and SiO 4 tetrahedra, respectively. The next phase transition occurs between 25 and 28 GPa and is accompanied by the symmetry change from monoclinic ( P 2 1 / c ) to orthorhombic ( Pna 2 1 ). The structure of paracelsian-III consists of SiO 6 octahedra, AlO 6 octahedra and distorted AlO 4 tetrahedra, i.e. the transition is reconstructive and associated with the changes of Si 4+ and Al 3+ coordination, which show rather complex behaviour with the general tendency towards increasing coordination numbers. The third phase transition is observed between 28 and 32 GPa and results in the symmetry decreasing from Pna 2 1 to Pn . The transition has a displacive character. In the course of the phase transformation pathway up to 32 GPa, the structure of polymorphs becomes denser: paracelsian-II is based upon elements of cubic and hexagonal close-packing arrangements of large O 2− and Ba 2+ ions, whereas, in the crystal structure of paracelsian-III and IV, this arrangement corresponds to 9-layer closest-packing with the layer sequence ABACACBCB .

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Raman spectroscopy, phase transitions, microstructures, and mechano‐luminescence in Ca‐Sr feldspars (CaAl₂Si₂O₈‐SrAl₂Si₂O₈)

Curetti,

Bernasconi,

Tribaudino

2024

J Raman Spectroscopy

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The Raman spectra of Ca1‐xSrxAl2Si2O8 (0 ≤ x ≤ 1) feldspars have been measured, to investigate at a short‐range scale the effect of changing composition on the P ➔ I and I ➔ I2/c phase transitions and how phase transitions affect the mechano‐luminescence found in these feldspars. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were done on the same samples, to pinpoint the transitions, by the analysis of selected area diffraction patterns (SAED) and of the spontaneous strain. Natural anorthite (CaAl2Si2O8) shows a large number of well‐resolved peaks, together with sharp h + k even, l odd diffractions (c‐type) in SAED patterns, indicative of a P symmetry. In synthetic anorthite, the Raman spectrum is similar to that of natural anorthite, but the peaks are broader, and c‐type reflections are elongated. As Sr increases, the c‐type reflections become more diffuse and elongated, as the Raman peaks do. At x > 0.6, new peaks appear in Raman spectra, and other peaks show a change in their wavenumber. Moreover, the c‐type reflections disappear completely, and the lattice becomes I‐centred. Between x ~ 0.6 and x = 0.86(3), the XRD patterns prompt for a triclinic structure, with S.G. I. The transition to the monoclinic I2/c structure is well constrained by the ferroelastic strain, whereas the Raman spectra are more similar between the monoclinic and triclinic I and I2/c than between I and P. The absence of mechano‐luminescence in triclinic I compositions suggests that this property is enhanced in local P configurations at conditions close to the P to I transition. A possible mechanism for mechano‐luminescence involving a compression induced P to I transition in local Eu2+ bearing P configurations is proposed.

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High-pressure structural configuration and phase transition in celsian, BaAl2Si2O8

Abstract: changes with compression in celsian are the deformation in the Ba polyhedra and the variation in the T-O-T angles.

Cited by 9 publications

References 30 publications

High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

High pressure phase transitions of paracelsian BaAl2Si2O8

Raman spectroscopy, phase transitions, microstructures, and mechano‐luminescence in Ca‐Sr feldspars (CaAl₂Si₂O₈‐SrAl₂Si₂O₈)

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High-pressure structural configuration and phase transition in celsian, BaAl2Si2O8

Abstract: changes with compression in celsian are the deformation in the Ba polyhedra and the variation in the T-O-T angles.

Cited by 9 publications

References 30 publications

High-pressure equation of state and phase transition in PbAl2Si2O8feldspar

High-pressure equation of state and phase transition in PbAl2Si2O8feldspar

High pressure phase transitions of paracelsian BaAl2Si2O8

Raman spectroscopy, phase transitions, microstructures, and mechano‐luminescence in Ca‐Sr feldspars (CaAl2Si2O8‐SrAl2Si2O8)

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High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

Raman spectroscopy, phase transitions, microstructures, and mechano‐luminescence in Ca‐Sr feldspars (CaAl₂Si₂O₈‐SrAl₂Si₂O₈)