Dielectric Spectroscopy at High Frequencies on Glass Forming Liquids

1996 ◽  
Vol 455 ◽  
Author(s):  
P. Lunkenhemer ◽  
A. Pimenov ◽  
M. Dressel ◽  
B. Gorshunov ◽  
U. Schneider ◽  
...  
Keyword(s):  
Light Scattering ◽  
Dielectric Loss ◽  
Propylene Carbonate ◽  
Dielectric Spectroscopy ◽  
Far Infrared ◽  
Relaxation Peak ◽  
Fast Process ◽  
High Frequencies ◽  
Glass Forming

ABSTRACTDielectric spectroscopy up to 950 GHz has been performed on various glass formers as glycerol, propylene-carbonate, and Salol. Special attention is given to the dielectric loss, ε″, in the crossover regime from the a-relaxation to the far-infrared (FIR) response where it can be directly compared to the dynamic susceptibilities obtained by neutron and light scattering techniques. We observe a minimum in ε″(ν) at high frequencies which cannot be explained by a simple transition from a-relaxation peak to the FIR bands but has to be attributed to additional fast processes. In all materials investigated, ε″(ν) increases significantly sublinear above the minimum. The ratio of the intensity of the α-process and the fast process as determined from our dielectric experiments is significantly higher compared to the results from the scattering experiments.

scholarly journals Broadband dielectric spectroscopy on glass-forming propylene carbonate

1999 ◽  
Vol 59 (6) ◽  
pp. 6924-6936 ◽  
Author(s):  
U. Schneider ◽  
P. Lunkenheimer ◽  
R. Brand ◽  
A. Loidl
Keyword(s):  
Propylene Carbonate ◽  
Dielectric Spectroscopy ◽  
Glass Forming ◽  
Broadband Dielectric Spectroscopy

Density and confinement effects of glass forming m-toluidine in nanoporous Vycor investigated by depolarized dynamic light scattering

2013 ◽  
Vol 138 (11) ◽  
pp. 114501 ◽  
Author(s):  
Thomas Blochowicz ◽  
Emmanuel Gouirand ◽  
Sebastian Schramm ◽  
Bernd Stühn
Keyword(s):  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Confinement Effects ◽  
Glass Forming

scholarly journals Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michela Romanini ◽  
Roberto Macovez ◽  
Maria Barrio ◽  
Josep Lluís Tamarit
Keyword(s):  
Glass Transition ◽  
Dielectric Loss ◽  
Dielectric Spectroscopy ◽  
Parent Compound ◽  
Scanning Calorimetry ◽  
Molecular Conformations ◽  
Molecular Glass ◽  
Phenyl Ketone ◽  
Temperature And Pressure ◽  
Opposite Chirality

AbstractWe employ temperature- and pressure-dependent dielectric spectroscopy, as well as differential scanning calorimetry, to characterize benzophenone and the singly-substituted ortho-bromobenzophenone derivative in the liquid and glass states, and analyze the results in terms of the molecular conformations reported for these molecules. Despite the significantly higher mass of the brominated derivative, its dynamic and calorimetric glass transition temperatures are only ten degrees higher than those of benzophenone. The kinetic fragility index of the halogenated molecule is lower than that of the parent compound, and is found to decrease with increasing pressure. By a detailed analysis of the dielectric loss spectra, we provide evidence for the existence of a Johari–Goldstein (JG) relaxation in both compounds, thus settling the controversy concerning the possible lack of a JG process in benzophenone and confirming the universality of this dielectric loss feature in molecular glass-formers. Both compounds also display an intramolecular relaxation, whose characteristic timescale appears to be correlated with that of the cooperative structural relaxation associated with the glass transition. The limited molecular flexibility of ortho-bromobenzophenone allows identifying the intramolecular relaxation as the inter-enantiomeric conversion between two isoenergetic conformers of opposite chirality, which only differ in the sign of the angle between the brominated aryl ring and the coplanar phenyl-ketone subunit. The observation by dielectric spectroscopy of a similar relaxation also in liquid benzophenone indicates that the inter-enantiomer conversion between the two isoenergetic helicoidal ground-state conformers of opposite chirality occurs via a transition state characterized by a coplanar phenyl-ketone moiety.

Light scattering measurement of shear viscosity in a fragile glass-forming liquid, metatoluidine

1998 ◽  
Vol 42 (1) ◽  
pp. 55-60 ◽  
Author(s):  
C Dreyfus ◽  
A Aouadi ◽  
R. M Pick ◽  
T Berger ◽  
A Patkowski ◽  
...  
Keyword(s):  
Light Scattering ◽  
Shear Viscosity ◽  
Glass Forming ◽  
Fragile Glass ◽  
Light Scattering Measurement ◽  
Scattering Measurement

Leveraging Glass Properties for Advanced Packaging

2015 ◽  
Vol 2015 (1) ◽  
pp. 000370-000374
Author(s):  
A.B. Shorey ◽  
Y.J. Lu ◽  
G.A. Smith
Keyword(s):  
Coefficient Of Thermal Expansion ◽  
Cost Effective ◽  
High Frequencies ◽  
Glass Substrates ◽  
Glass Forming ◽  
Cost Structures ◽  
Advanced Packaging ◽  
Downstream Processes ◽  
Electrical Loss ◽  
Made In

Glass provides many opportunities for advanced packaging. The most obvious advantage is given by the material properties. As an insulator, glass has low electrical loss, particularly at high frequencies. The relatively high stiffness and ability to adjust the coefficient of thermal expansion gives advantages to manage warp in glass core substrates and bonded stacks for both through glass vias (TGV) and carrier applications. Glass also gives advantages for developing cost effective solutions. Glass forming processes allow the potential to form both in panel format as well as at thicknesses as low as 100 um, giving opportunities to optimize or eliminate current manufacturing methods. As the industry adopts glass solutions, significant advancements have been made in downstream processes such as glass handling and via/surface metallization. Of particular interest is the ability to leverage tool sets and processes for panel fabrication to enable cost structures desired by the industry. By utilizing the stiffness and adjustable CTE of glass substrates, as well as continuously reducing via size that can be made in a panel format, opportunities to manufacture glass TGV substrates in a panel format increase. We will provide an update on advancements in these areas as well as handling techniques to achieve desired process flows. We will also provide the latest demonstrations of electrical, thermal and mechanical reliability.

scholarly journals Light-scattering study of the liquid-glass transition in propylene carbonate

1994 ◽  
Vol 49 (3) ◽  
pp. 2192-2205 ◽  
Author(s):  
W. M. Du ◽  
G. Li ◽  
H. Z. Cummins ◽  
M. Fuchs ◽  
J. Toulouse ◽  
...  
Keyword(s):  
Glass Transition ◽  
Light Scattering ◽  
Propylene Carbonate ◽  
Liquid Glass ◽  
Scattering Study
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