Do tunneling states and boson peak persist or disappear in extremely stabilized glasses?

We review and concurrently discuss two recent works conducted by us, which apparently give opposite results. Specifically, we have investigated how extreme thermal histories in glasses can affect their universal properties at low temperatures, by studying: (i) amber, the fossilized natural resin, which is a glass which has experienced a hyperaging process for about one hundred million years; and (ii) ultrastable thin-film glasses of indomethacin. Specific heat Cp measurements in the temperature range 0.07 K < T < 30 K showed that the amount of two-level systems, assessed from the linear term at the lowest temperatures, was exactly the same for the pristine hyperaged amber glass as for the subsequently rejuvenated samples, whereas just a modest increase of the boson-peak height (in Cp/T³) with increasing rejuvenation was observed, related to a corresponding increase of the Debye coefficient. On the other hand, we have observed an unexpected suppression of the two-level systems in the ultrastable glass of indomethacin, whereas conventionally prepared thin films of the same material exhibit the usual linear term in the specific heat below 1 K ascribed to these universal two-level systems in glasses. By comparing both highly-stable kinds of glass, we conclude that the disappearance of the tunneling two-level systems in ultrastable thin films of indomethacin may be due to the quasi-2D and anisotropic behavior of this glass, what could support the idea of a phonon-mediated interaction between two-level systems

Low-temperature properties of monoalcohol glasses and crystals

We review and jointly discuss both earlier and recent experiments conducted by us on simple aliphatic glass-forming monoalcohols at low temperatures, including specific heat, thermal conductivity, Brillouin scattering and x-ray diffraction experiments. The family of simple monoalcohols constitutes an interesting model system to explore different relevant issues concerning molecular glass-forming liquids, low-temperature universal proper-ties of glasses, and even the glass transition phenomenon itself. More specifically, we discuss the role played by the molecular aspect ratio in vitrification/crystallization kinetics, the reported appearance of particular cases of polymorphism (in ethanol) and polyamorphism (in butanol), and especially the influence of position isomerism and the location of the hydrogen bond on the lattice dynamics and hence on the low-temperature universal prop-erties of glasses

Influence of the yttria content on the mechanical properties of Y2O3-ZrO2 thin films prepared by EB-PVD

A mechanical characterization study of the whole range (ZrO2)1−x–(Y2O3)x system is presented for thin film samples. Films have been prepared by Electron Beam Physical Vapour Deposition (EB-PVD) on Si(1 0 0) substrates. The mechanical characterization, obtained from nanoindentation and Brillouin Light scattering (BLS) techniques, shows a monotonous behaviour between the two pure compounds of the series except for the film with 0.08 Y2O3 molar content of yttria-stabilized zirconia (YSZ) solid solution that presents an anomalous hard value. Additionally, BLS is presented as an alternative technique to the study of the mechanical properties of this system.Dirección General de Investigación Científica y Técnica (DGICYT) MAT2003-6147-C04-01Dirección General de Investigación Científica y Técnica (DGICYT) MAT2003-6147-C04-0

Crystalline phase transitions and acoustic phonons behaviour of polymorphic ethanol

78.35.+c Brillouin and Rayleigh scattering; other light scattering, 87.19.rd Elastic properties, 64.60.My Metastable phases, 64.70.kt Molecular crystals,