New insights into the high-pressure polymorphism of SiO2 cristobalite

Dera, Przemysław; Lazarz, John D.; Prakapenka, Vitali B.; Barkley, Madison C.; Downs, Robert T.

doi:10.1007/s00269-011-0424-5

Cited by 66 publications

(57 citation statements)

References 22 publications

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“…If this is the case, coesite II appears above 31 GPa as an " overpressurized " phase out of its (meta)stability field. A similar behavior was seen in cristobalite I, which compresses smoothly far out of its stability field, suppressing the formation of the more stable high-pressure polymorph cristobalite II [32] .…”

Section: Si2-o15-si3mentioning

confidence: 52%

High-pressure crystal chemistry of coesite-I and its transition to coesite-II

Černok

Bykova

Ballaran

et al. 2014

Zeitschrift Für Kristallographie - Crystalline Materials

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The high-pressure crystal chemistry of coesite was studied by means of single crystal X-ray diffraction in the pressure interval ∼ 2 -34 GPa and at ambient temperature. We compressed the samples using diamond-anvil cells loaded with neon as pressure-transmitting medium and collected X-ray diffraction data using synchrotron radiation. The thermodynamically stable coesite -coesite-I -was observed up to ∼ 20 GPa, with the following unit-cell parameters: a = 6.6533(12) Å , b = 11.9018(10) Å , c = 6.9336(10) Å , β = 121.250(20) ° and V = 469.38(15) Å 3 . The volume-pressure data of coesite-I are described by means of a third-order Birch-Murnhagan EoS with parameters V 0 = 547.26(66) Å 3 ,. Above such pressure we witness the formation of a well crystallized coesite-II, previously observed only by spectroscopic studies. The structure of the novel high-P polymorph was determined and refined at ∼ 28 and ∼ 31 GPa with final R indices of 8% and 12%, respectively. Coesite-II has P 2 1 /n symmetry and a unit cell that is " doubled " along the b -axis with respect to that of the initial coesite-I: a = 6.5591(10) Å , b = 23.2276(14) Å , c = 6.7953(9) Å , β = 121.062(19) ° and V = 886.84(19) Å 3 at ∼ 28 GPa. All Si atoms are in tetrahedral coordination. The displacive phase transition I-> II is likely driven by the extreme shortening (0.05 Å or 3.2%) of the shortest and the most compressible Si1-O1 bond, related to the stiff 180 ° Si1-O1-Si1 angle. Under compression the linear angle bends, resulting in two independent angles, one of which, however, retains almost linear geometry ( ∼ 178 ° ). The requirement of this angle to be close to linear likely causes further Si-O compression down to an extremely short distance of ∼ 1.52 Å which prompts subsequent structural changes, with the formation of a triclinic phase at ∼ 31 GPa, coesite-III.

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Section: Si2-o15-si3mentioning

confidence: 52%

High-pressure crystal chemistry of coesite-I and its transition to coesite-II

Černok

Bykova

Ballaran

et al. 2014

Zeitschrift Für Kristallographie - Crystalline Materials

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“…In helium pressure medium, which provides higher hydrostaticity, polycrystalline quartz is found to remain crystalline up to 45 GPa and to transform to a monoclinic phase at such pressure (Haines et al 2001). A transformation path through several metastable phases has been reported in cristobalite, as well (e.g., Yagi and Yamakata 2000;Prokopenko et al 2001;Dera et al 2011). Numerical calculations also stressed the fact that stable polymorphs of SiO 2 may undergo several phase transitions to metastable phases with increasing pressure before reaching amorphization (Teter and Hemley 1998;Wentzcovitch et al 1998;Dean et al 2000).…”

Section: Introductionmentioning

confidence: 78%

Pressure-induced phase transitions in coesite

Černok

Ballaran

Caracas

et al. 2014

American Mineralogist

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High-pressure behavior of coesite was studied on single crystals using diamond-anvil cells with neon as the pressure-transmitting medium by means of in situ Raman spectroscopy up to pressures of ~51 GPa. The experimental observations were complemented with theoretical computations of the Raman spectra under similar pressure conditions. We find that coesite undergoes two phase transitions and does not become amorphous at least up to ~51 GPa. The first phase transition (coesite I to coesite II) is reversible and occurs around 23 GPa. The second transition (coesite II to coesite III) at about 35 GPa is also reversible but involves a large hysteresis. Samples recovered from the highest pressure achieved, ~51 GPa, show Raman spectra of the initial coesite. The ab initio calculations gave insight into the initiation mechanism of the first phase transition, implying, from the analysis of unstable phonon modes, that it is probably a displacive phase transition due to shearing of the four-membered rings of SiO 4 tetrahedra upon compression. The transition to the lowest-symmetry phase, coesite III, is possibly a first-order phase transition that leads to a very distinct structure. None of the metastable high-pressure phases of coesite has been previously studied and it was widely accepted that coesite undergoes pressure-induced amorphization at significantly lower pressures (30 GPa). The study of the high-pressure behavior of coesite is important to better constrain the metastable phase diagram of silica. Further crystallographic investigations are necessary for characterizing the structures of these metastable coesite forms. Crystalline or amorphous metastable phases derived from coesite under high-pressure conditions are of particular interest because they can be used as potential tracers of peak transient pressures (stress) reached in processes such as impacts or faulting.

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“…The standard crystallographic data for the refinement of m-ZrO2, t-ZrO2, c-ZrO2, ZrSiO4 and c-SiO2 were obtained from Smith et.al., 18 Howard et.al., 19 Wyckoff, 20 Hazen et.al. 21 and Dera et al 22 respectively. The procedure for structural refinement was carried out in accordance with the previous report by the authors.…”

Section: Powder Characterizationmentioning

confidence: 99%

Tetragonal to Cubic Transformation of SiO₂-Stabilized ZrO₂ Polymorph through Dysprosium Substitutions

2017

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Partially stabilized tetragonal zirconia (t-ZrO2) is of particular interest for hard tissue replacements. Ageing related failures of the ceramic associated with the gradual transformation from t-ZrO2 to m-ZrO2 (monoclinic zirconia) can lead to its premature removal from the implant site. In addition, monitoring the satisfactory performance of the implant throughout its life span without invasive techniques is a challenging task. The magnetic resonance imaging (MRI) contrast ability of dysprosium (Dy 3+ ) is well established. To this aim, varied levels of Dy 3+ additions in the ZrO2-SiO2 binary oxide system have been explored. The results indicate the effective role of Dy 3+ in the formation of thermally and mechanically stable c-ZrO2 (cubic zirconia) phase at higher temperatures. The presence of SiO2 influenced the t-ZrO2 stabilization whereas Dy 3+ tends to occupy the ZrO2 lattice sites to induce c-ZrO2 transition. Magnetic and magnetic resonance imaging (MRI) tests displayed the commendable contrast ability of Dy 3+ stabilized ZrO2-SiO2 binary systems. Nanoindentation results demonstrate a remarkable enhancement on the mechanical properties.Keywords: Silica; Zirconia; Dysprosium; Stabilization; Mechanical. 3 IntroductionThe demand for bone implants is growing rapidly due to the increasing incidents of trauma and age related defects caused by osteoporosis. In view of the above potential advantages of Dy 3+ as an addition to ZrO2-SiO2 binary oxides in terms of increased t-ZrO2 stability and enhance MRI image contrast, we present a study of the influence of Dy 3+ on the ZrO2-SiO2 binary oxide system through in-situ sol-gel synthesis, followed by a systematic analysis of the resulting phase composition and structure, mechanical strength and imaging contrast features. Materials and Methods Powder synthesisThe synthesis of Dy 3+ doped ZrO2-SiO2 (DZS) binary oxides was achieved through the sol-gel method. Analytical grade Dy(NO3)3.H2O, ZrOCl2·8H2O and (C2H5)4OSi (TEOS), all procured from Sigma-Aldrich, India, were taken as precursors for the synthesis. The molar concentrations of ZrOCl2·8H2O and (C2H5)4OSi were maintained at a constant ratio of 1: 1 throughout the 5 synthesis whereas the Dy(NO3)3 additions were adjusted to obtain a wide range of compositions.Additionally, a pure ZrO2-SiO2 binary with 1:1 molar ratio was prepared for comparative purposes. The molar concentrations of the different precursors and the respective sample codes are reported in Table 1; the same codes will be used throughout the manuscript. The synthetic procedure is briefly explained as follows. Previously prepared Dy(NO3)3 stock solution as detailed in Table 1 was added to the ZrOCl2 solution under vigorous stirring. The required amount of ethanol was added to this continuously stirred mixture at an operating temperature of 80 °C for 30 minutes. This was followed by the addition of 1 M TEOS to the solution under constant stirring conditions and finally 0.1 M of HNO3 was added to this mixture as a catalyst. The homogeneous solut...

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New insights into the high-pressure polymorphism of SiO2 cristobalite

Cited by 66 publications

References 22 publications

High-pressure crystal chemistry of coesite-I and its transition to coesite-II

High-pressure crystal chemistry of coesite-I and its transition to coesite-II

Pressure-induced phase transitions in coesite

Tetragonal to Cubic Transformation of SiO₂-Stabilized ZrO₂ Polymorph through Dysprosium Substitutions

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New insights into the high-pressure polymorphism of SiO2 cristobalite

Cited by 66 publications

References 22 publications

High-pressure crystal chemistry of coesite-I and its transition to coesite-II

High-pressure crystal chemistry of coesite-I and its transition to coesite-II

Pressure-induced phase transitions in coesite

Tetragonal to Cubic Transformation of SiO2-Stabilized ZrO2 Polymorph through Dysprosium Substitutions

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Product

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Tetragonal to Cubic Transformation of SiO₂-Stabilized ZrO₂ Polymorph through Dysprosium Substitutions