Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    The degree and nature of radiation damage in zircon observed by 29Si nuclear magnetic resonance (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2084-2090 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantitative analysis of 29Si nuclear magnetic resonance spectra of radiation damaged, natural zircons showed that the local structure in crystalline and amorphous regions depend explicitly on radiation dose. Nonpercolating amorphous islands of high density "glass" within the crystalline matrix show a low interconnectivity of SiO4 tetrahedra. This structural state is quite different from that of the high dose, percolating regions of low density glass with more polymerised tetrahedra. A continuous nonlinear dose dependence between the high and low density glass states is reported. A continuous evolution of the local structure of the crystalline phase up to the percolation point is also reported. No phase separation into binary oxides was observed. The total number of permanently displaced atoms per α-recoil event is ∼3800 atoms for low radiation doses and decreases to ∼2000 atoms for 10×1018 α events/g. No indication of partitioning of paramagnetic impurities between crystalline and amorphous regions was found for these natural zircons. The amorphous fractions of the metamict zircons were determined as a function of their accumulated radiation dose. These values coincide closely with those recently determined by x-ray diffraction studies. They are much greater than previously assumed based on density measurements. The dose dependence is consistent with the concept of direct impact amorphization in the atomic cascade following an α-recoil event. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1343523
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    MESO – a program to convert X-ray diffraction data from angular to reciprocal space (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 362-364 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A computer code has been developed to convert X-ray diffraction data generated by Siemens X-1000 and Siemens HISTAR area detectors and INEL CPS 120 linear detectors from angular to reciprocal space. Programs have been written to visualize and analyse the resulting data using AVS (Advanced Visual Systems Inc., MA, USA). Two examples of the application of MESO to problems in X-ray diffuse scattering are presented. Firstly, the `butterfly' associated with tweed microstructure in the high-temperature superconductor YBa2(Cu1–xMx)3O7–δ. Secondly, the `dog bone' generated by scattering off domain walls in the perovskite-like WO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889898017221
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Crystallography and structural phase transitions, an introduction (1991)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 453-469 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Structural phase transitions which involve the generation of lattice strain (i.e. in ferroelastic and co-elastic crystals) are reviewed. Landau–Ginzburg theory is found to lead to an appropriate description of order parameters following the theoretical predictions over large temperature intervals. A quantum extension of Landau–Ginzburg theory is presented which describes the saturation of order parameters at low temperatures. Coupling between different order parameters is relevant if more than one phase transition (or lattice instability) occurs in a crystal. Finally, the importance of microstructures and kinetic processes for the structural behaviour of crystals is pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767391004300
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Lattice parameters, spontaneous strain and phase transitions in Pb3(PO4)2 (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 387-392 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768192008127
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Al,Ge cation ordering in BaAl2Ge2O8-feldspar: monodomain ordering kinetics (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 203-212 
    Details
    ISSN: 1432-2021
    Keywords: Key words Kinetics ; Feldspar ; Fluctuations ; BaAl2Ge2O8 ; Partial conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The kinetics of monodomain order-disorder processes in monoclinic (I2/c) BaAl2Ge2O8-feldspar have been investigated by X-ray powder diffraction, Hard Mode IR Spectroscopy, and TEM darkfield imaging on quenched samples. Compared to the behaviour predicted by the TDGL approximation ordering kinetics observed at low temperatures slow down significantly when equilibrium is approached. Such a delay is not observed in disordering experiments starting from essentially ordered cation distributions. The deviation from TDGL behaviour is interpreted in terms of partial order parameter conservation in a non-uniformly ordered phase. Modifications to the uniform TDGL rate equation are tested against the available data. An activation energy of 352 ± 28 kJ/mol is obtained for Al,Ge ordering. The mixing coefficient ξc 2/ξ2, which describes the degree of order parameter conservation, is obtained as a function of temperature. While this coefficient vanishes in the vicinity of the transformation temperature T tr, it saturates towards a level of ξc 2/ξ2≈0.4 for T→0. ξ c 2/ξ2 determines the kinetic stability of ordered clusters quenched from T≈T tr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050008
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Thermally induced phase transitions in tridymite: an infrared spectroscopy study (1995)
    Springer
    Physics and chemistry of minerals 22 (1995), S. 50-60 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The temperature dependence of the infrared active modes of meteoritic and synthetic tridymite have been investigated between 23 K and 1073 K in IR absorption and IR emission experiments. At room temperature both tridymite samples consist of a mixture of low temperature forms, in different proportions, due to the grinding. The sequence of phase transitions in Steinbach tridymite deduced from the IR data agrees well with recent X-ray and calorimetry studies using identical samples (Cellai et al. 1994). The previously suspected structural phase transition P6322⇔P63/mmc is confirmed by the disappearance of the 470 cm-1 mode and a temperature anomaly of the spectral shift of the 790 cm-1 mode. Changes in the infrared spectra of synthetic tridymite give a different sequence of phase transitions from those of the meteoritic sample, consistent with the structural phase transitions observed in a 29Si MAS NMR investigation using the same sample (Xiao et al. 1993).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202680
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Phase transition(s) in titanite CaTiSiO5: An infrared spectroscopic, dielectric response and heat capacity study (1995)
    Springer
    Physics and chemistry of minerals 22 (1995), S. 41-49 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The structural phase transition in titanite near 500 K (averaged symmetries A2/a→P2 1/a) and a second anomaly around 900 K have been studied using infrared spectroscopy on single crystals aqnd powder samples, measurements of the dielectric properties and the specific heat. The same synthetic single crystal was used in all experiments. The phase transition near 500 K is associated with a break in the temperature evolution of phonon frequencies and absorption intensities. Some phonon signals decrease rapidly under further heating and their extrapolated intensities disappear at ca. 850 K. The most dominant temperature effect relates to Ti-O phonons with amplitudes along the crystallographic a axis. These phonons show large LO-To splitting and continue to soften under heating even at temperatures above the transitions point (ca. 500 K). The softening of these modes correlates directly with the increase of the real part of the dielectric constant with a well-pronounced anomaly at 500 K. The dielectric losses also increse with increasing temperature. Measurements under strong field do not show antiferroelectricity. The transition at 500 K generates a small but sharp λ-anomaly in the excess specific heat. A second, weaker anomaly was found near 850 K. The results are discussed in terms of thermodynamic models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202679
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    An infrared spectroscopic and single-crystal X-ray study of malayaite, CaSnSiO5 (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 546-553 
    Details
    ISSN: 1432-2021
    Keywords: Key words Malayaite ; Infrared spectroscopy ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Powder infrared spectroscopy and X-ray diffraction techniques on single crystals were used to study the thermal behaviour of malayaite, CaSnSiO5. Infrared spectra show a discontinuity in the temperature evolution of phonon frequencies and absorbance near 500 K. However, crystal structure data collected at 300, 450, 550, 670, and 750 K show no evidence of a symmetry-breaking phase transition and no split positions. The most obvious change with heating is a tumbling motion of the SnO6 octahedra and an increase of the anisotropic displacement factors of Ca. The thermal evolution of the mean-square vibrational amplitude of the Ca atom shows a pronounced change in slope near 500 K. The evidence suggests that the 500 K anomaly in malayaite is more similar in character to the 825 K (β-γ) transition as opposed to the 496 K (α-β) transition in synthetic titanite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050218
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Time evolution of twin domains in cordierite: a computer simulation study (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 275-296 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cordierite ; Twin structure ; Time evolution ; Domain ; Computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  The time and temperature evolution of twinning in cordierite is simulated using three computer models. The orientation of walls between twin domains in natural cordierite follows mainly the ferroelastic pattern which minimises the strain energy of the walls between twin-related domains. Such ferroelastic twinning is simulated in an elastic three-states Potts model in which each structural six-membered ring is represented by a three state pseudo-spin. The resulting twin pattern in a sample with 3169 structural rings shows sector trilling and fine scale ferroelastic wall patterns which coarsen with increasing annealing time. The poorly defined wall directions observed in cordierite were found to be related to twin walls which do not minimise the strain energy. Instead, these walls are located along the corners of pseudo-hexagonal rings and appear as the consequence of local rather than global interatomic interactions. Simulations using two-dimensional (38028 atoms) and three-dimensional (408 228 atoms) structural models show a predominance of these topological walls over the strain walls at early stages in the ordering process. The domain structure in the simulation is patchy rather than corresponding to repeated stripe structures found in other ferroelastic and co-elastic materials. In all models, a strong tendency for sector trilling is observed. In kinetic tweed patterns a novel 60º tweed is found at atomic length scales while the usual strain-mediated 90º tweed appears at mesoscopic length scales. An unusual surface tension effect in domain formation and ’writhing’, fluid-like motion was found in the three-dimensional structural model. This motion, along with the existence of non strain-mediated walls may contribute to cordierite’s poorly defined domain wall directions at the early stages of domain coarsening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050188
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Cation ordering in BaAl2Ge2O8-feldspar: implications for the phase transition in anorthite (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 354-366 
    Details
    ISSN: 1432-2021
    Keywords: Key words Phase transition ; Anorthite ; Ising-Model ; BaAl2Ge2O8
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  BaAl2Ge2O8-Feldspar undergoes an order-disorder phase transition I2/c↔C2/m at T tr ≈1690 K. The thermodynamics of the Al,Ge cation ordering process is described in terms of the compressible Ising model in mean field approximation. The mean field potential predicts a first order character of the phase transition. This is compared to antiferromagnetic ordering in a two-dimensional square Ising model with NN-pair interactions and four-spin interactions on alternating squares. Calculated order parameters and short range ordering are in good agreement with the corresponding properties observed in BaAl2Ge2O8-feldspar by means of X-ray diffraction, hard mode infrared spectroscopy and TEM. Using known calorimetric data a similar model is postulated for Al,Si ordering in anorthite, CaAl2Si2O8, for which the derived potential describes a transition with slightly stronger first order character at T tr ≈1928 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050195
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...