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Aluminate glasses containing 45–71.5 mol% alumina, 10–40 mol% rare earth oxide, and 0–30 mol% silica were synthesized from precursor oxides. The glass transition and crystallization temperatures were determined by differential scanning calorimetry; the structural and mechanical properties were investigated by Raman and Brillouin spectroscopy. The range of the supercooled liquid region varies from ∼40 °C to 200 °C, providing a useful working range for compositions with 5–30 mol% silica. Raman scattering showed the presence of isolated SiO 4 species that strengthen the network-forming structure, enhance glass formation, and stabilize the glass even when they are present at fairly low concentrations. Sound velocities were measured by Brillouin scattering. From these and other values, various elastic moduli were calculated. The moduli increased with both aluminum and rare earth content, as did the hardness of the glasses. Young’s modulus was in the range 118–169 GPa, 60–130% larger than that for pure silica glass.

The Brillouin spectroscopic measurements of elastic properties of polypropylene films fabricated by different processing techniques are described. We find that the elastic symmetry and the associated elastic constants are dependent on the molecular orientation brought about by the processing conditions used to produce the films. We have shown that Brillouin scattering techniques can successfully be used to track the molecular orientation induced by uniaxial stretching. We find a direct correspondence between the Brillouin measurements and optical birefringence measurements, illustrating that molecular orientation plays a dominant role in determining the mechanical anisotropy in these materials.

Brillouin scattering results from the interaction of photons with thermal excitations in a medium. The energy and propagation direction of the photons are modified by the interaction giving rise to a measurable frequency shift. Because the excitations are not related to the order existing in the medium, they can be observed in gases, fluids, or solids, ordered (crystals) as well as disordered (amorphous or glasses). In crystals, the measured frequency shift depends on the propagation direction of the excitations (phonons). Hence, Brillouin scattering is well adapted to study phase transitions, driven either by pressure, temperature, or a combination of them. The use of the technique is illustrated by two examples: berlinites under pressure, and a high temperature study of silicate melts.

Changes in the elastic properties of Ge induced by room-temperature irradiation with 3.5-MeV Kr ions have been determined and correlated with changes in the microstructure determined by transmission electron microscopy. Elastic-shear-moduli changes were measured by Brillouin scattering, and changes in local atomic arrangement were determined by Raman scattering. Amorphization decreased the elastic shear modulus of Ge by 17%. The fractional decrease was correlated with the amorphous volume fraction with a cross section of 4.5\ifmmode\pm\else\textpm\fi{}0.5 ${\mathrm{nm}}^{2}$/ion. No change was observed in the shear modulus during void formation and growth. The elastic properties of the voided material are described by the Voigt averaging. However, as the voids evolved into a fibrous spongelike microstructure, a second dramatic elastic softening occurs which we attribute to the inability of the fibrous structure to support shear stresses. Raman scattering showed that, once formed, there was no change in the structure of the amorphous material at the atomic scale during void formation and subsequent void coalescence.

Brillouin scattering from single crystals of NiO show that, apart from the expected phonon peaks, there is a broad central peak. The phonon peaks have Fano-like lineshapes, indicating a strong coupling between them and the broad feature, and lead to elastic constants that differ considerably from ultrasonic values. The broad feature is probably ‘magnetic’ in origin since it disappears at the Neel temperature. We speculate that it may be the lower of the two AFMR modes predicted for easy-plane antiferromagnets but which has previously been observed only in EuTe and MnO. The interaction between the phonons and the ‘magnetic’ excitation provides a phenomenological explanation for the differences in the elastic constants determined by different techniques.

Brillouin scattering measurements have been carried out on single‐crystal lattice‐matched TiN/(V0.6Nb0.4)N and mismatched TiN/NbN superlattices. Measured surface wave velocities were found to be independent of superlattice wavelength over the entire range investigated, 1.5–30 nm, and were averages of the measured velocities of pure homogeneous TiN, NbN, and (V0.6Nb0.4)N. These results indicate that there is no anomaly in the C44 elastic constant. X‐ray diffraction results from the superlattices indicated that the average lattice spacing did not vary with wavelength. This is consistent with previous observations where elastic anomalies were related to changes in lattice spacing. The absence of a correlation between the C44 elastic constant and previously reported hardness enhancements indicates that the latter are not caused by anomalies in C44; they could, however, be correlated with other elastic moduli.

The shear elastic modulus and structural properties of a series of Ag Co superlattice films have been characterized using Brillouin scattering and X-ray diffraction. A softening of the shear modulus of the unirradiated Ag Co superlattices with decreasing modulation wavelength is observed and is correlated with an expansion in the average lattice spacing. With increasing irradiation fluence, a reduction in the anomalous shear modulus softening and lattice expansion are observed. These reductions imply that the anomalous elastic properties are related to lattice strains present, which are relieved by the irradiation.

The modulation wavelength dependence of the surface‐wave velocity in Cu/Ni superlattices has been investigated using Brillouin scattering. It is the first compositionally modulated system to be studied by this technique and the first for which elastic properties have been determined by both ‘‘macroscopic’’ methods and Brillouin scattering. Contrary to the enhancements previously reported in the biaxial modulus and in the Young’s modulus, the modulus associated with the surface‐wave velocity shows no evidence of anomalous behavior.

We have used Brillouin scattering to measure the temperature dependence of the sound velocities of the longitudinal and transverse vibrational modes in various directions in small single crystals of monoclinic ZrO2. Using these velocities and the Christoffel equation, we have calculated the 13 elastic stiffness moduli between room temperature and the monoclinic—tetragonal transformation temperature.

We discuss here the complete determination of the elastic properties of a polyimide film using two experimental techniques. One technique employs the polymer film as a vibrating membrane and allows a direct determination of the ’macroscopic’ biaxial modulus. Brillouin scattering, which measures the elastic properties on a ∼ 100 μ scale, allows for a complete characterization of the elastic behavior. The results obtained by the two techniques are in agreement within the reported error bars.

Using Brillouin scattering we have succeeded in observing the normal modes of vibration of unsupported films in a region where the dispersion relationship is quadratic. Extremely low-lying excitations were observed in thin films with thicknesses as small as 200 A\r{}. Contrary to what has been found in work on supported films, we are able to extract information on a number of the elastic moduli because the measured velocities in very thin films do not depend on the properties of the substrate. This technique should be a valuable addition to the tools which can be used in the study of materials in thin-film form.

Using Brillouin scattering, we have measured the sound velocity in fluid and solid helium 4 at room temperature up to 20 GPa. Our results show that the pair potentials currently used to describe helium are inadequate. The density of the fluid is determined as a function of pressure up to the fusion point. In the solid, the sound velocity and the elastic anisotropy are compared with lattice dynamics calculations.

The crystalline-to-amorphous (c-a) phase transformation in the intermetallic compound Zr 3 Al during room temperature bombardment with 1.0 MeV Kr + was investigated. Transmission electron microscopy and Brillouin scattering techniques were used to determine the lattice parameter and shear elastic constant as a function of the degree of long-range order. The results show that a large (about 50%) elastic softening and dilatation strain (about 3%) due to disordering precede the onset of amorphization. These results indicate that chemical disordering is an important driving force for the c-a transformation and that the mechanism is an elastic shear instability. It is also shown that the volume dependence of the shear elastic constant associated with radiation-induced disordering and eventual amorphization is virtually identical to that associated with the heating to melting of many solids. The origin and implications of this parallelism between solid state amorphization and melting are discussed.

We report the investigation of Brillouin scattering from thermal surface acoustic waves on Ag-coated holographic gratings. The usual wave-vector conservation condition for Brillouin scattering is modified due to the added periodicity in the direction of phonon propagation, but this effect is observed only when surface plasmons act as an intermediate state in the scattering process. The involvement of surface plasmons results in an enhancement of the Brillouin scattering cross section which depends on the grating amplitude.

We have performed a study of magnons in Mo/Ni metallic superlattices with the use of Brillouin scattering. The magnetic field and modulation wavelength dependence of the magnon frequencies are found to be in reasonable agreement with theoretical predictions. Certain features in the spectra which are characteristic of a superlattice and cannot be expalined by a trivial superposition of the spectra of the individual constituent layers are presented and discussed.

International audience; The properties of solid krypton have been measured as a function of pressure in a diamond-anvil cell using energy-dispersive x-ray diffraction and Brillouin scattering. A room-temperature equation of state and a complete set of elastic constants are deduced. The analysis of these results indicates a possible phase transition above 30 GPa.

The results of a Brillouin scattering study of the room temperature phases of H2;O (liquid, ice VI and ice VII) up to 30 GPa are presented. Longitudinal elastic moduli thus obtained are compared with values of the bulk modulus obtained from density measurements [1] and with both static and molecular dynamics calculations of the bulk modulus using potentials which have been proposed in studies of the liquid state. The calculations indicate that the potentials are not capable of describing the high pressure region of ice VII.

Brillouin scattering in GaS crystals had been measured under hydrostatic pressures up to 17.5 GPa. Frequency shifts of the Brillouin lines give the pressure dependence of the elastic constants C11 and C33, and the index birefringence. Exponents derived from Murnaghan’s equation of state are compared with a Lennard‐Jones description of interatomic forces in GaS.