Raman scattering boson peak and differential scanning calorimetry studies of the glass transition in tellurium-zinc oxide glasses

Vibrational properties of quasi-two-dimensional colloidal glasses with varying interparticle attraction

We measure the vibrational modes and particle dynamics of quasi-two-dimensional colloidal glasses as a function of interparticle interaction strength. The interparticle attractions are controlled via a temperature-tunable depletion interaction. Specifically, the interparticle attraction energy is increased gradually from a very small value (nearly hard-sphere) to moderate strength (∼4k_{B}T), and the variation of colloidal particle dynamics and vibrations are concurrently probed. The particle dynamics slow monotonically with increasing attraction strength, and the particle motions saturate for strengths greater than ∼2k_{B}T, i.e., as the system evolves from a nearly repulsive glass to an attractive glass. The shape of the phonon density of states is revealed to change with increasing attraction strength, and the number of low-frequency modes exhibits a crossover for glasses with weak compared to strong interparticle attraction at a threshold of ∼2k_{B}T. This variation in the properties of the low-frequency vibrational modes suggests a new means for distinguishing between repulsive and attractive glass states.

Structural and optical characterization of the local environment of Er3+ ions in PbO-ZnO tellurite glasses

Erbium activated PbO-ZnO tellurite glasses ((70TeO(2)-(30-x)ZnO-xPbO)(0.99)-(Er(2)O(3))(0.01) (TZPE), (x = 5, 10, 15, 20)) were prepared by a melt quenching process and studied by optical absorption, luminescence, Raman and x-ray absorption spectroscopy measurements as a function of the PbO/ZnO ratio. The glass structure, as monitored by Raman scattering, shows important changes with the PbO/ZnO ratio, attributed to a glass former action of PbO. The local environment of Er(3+) ions, as measured by extended x-ray absorption spectroscopy, does not appreciably change as regards the first oxygen shell. However, the intensity of the optical transitions is quite sensitive to the PbO/ZnO ratio, indicating a progressive increase of the site symmetry with the PbO content. The emission probability and radiative lifetime of several excited states of Er(3+) ions were calculated using Judd-Ofelt analysis.