Showing papers by "Stanislav V. Sinogeikin published in 2005"

Brillouin scattering study on the single-crystal elastic properties of natrolite and analcime zeolites

Abstract: The Brillouin light-scattering technique was used to investigate the single-crystal elastic properties of two aluminosilicate zeolites, natrolite (NAT) and analcime (ANA), at ambient conditions. An inversion of the acoustic velocity data results in the full set of elastic stiffness moduli (Cij’s) for both materials. From the single-crystal moduli the aggregate adiabatic bulk moduli (Ks), shear moduli (G), and Poisson’s ratios (ν) were found to be Ks=48.5(1.0)GPa, G=31.6(1.0)GPa, and ν=0.232(5) for NAT, and Ks=59.8(1.2)GPa, G=32.1(1.0)GPa, and ν=0.272(5) for ANA (Voigt-Reuss-Hill averages). The bulk and shear moduli of both zeolites are relatively low compared with those of densely packed aluminosilicates, reflecting an open framework structure of (Al,SiO4) tetrahedra which is easily deformed by bending the Si–O–Al angles. As expected for a less dense crystal, NAT is softer and more compressible than ANA. An evaluation of the directional Young’s moduli shows that the compressibility of NAT is nearly unifor...

High-pressure sound velocities and elasticity of aluminous MgSiO3 perovskite to 45 GPa: Implications for lateral heterogeneity in Earth's lower mantle

Abstract: [1] Brillouin scattering measurements on aluminous magnesium silicate perovskite, arguably the most abundant phase in Earth, have been performed to 45 GPa in a diamond anvil cell at room temperature, using methanol-ethanol-water and neon as pressure transmitting media. The experiments were performed on a polycrystalline sample of aluminous MgSiO3 perovskite containing 5.1 ± 0.2 wt.% Al2O3. The pressure derivatives of the adiabatic bulk (K0S) and shear (μ0S) moduli are 3.7 ± 0.3 and 1.7 ± 0.2, respectively. These measurements allow us to evaluate whether the observed lateral variations of seismic wave speeds in Earth's lower mantle are due at least in part to a chemical origin. Our results indicate that a difference in the aluminum content of silicate perovskite, reflecting a variation in overall chemistry, is a plausible candidate for such seismic heterogeneity.

High temperature elasticity measurements on oxides by Brillouin spectroscopy with resistive and IR laser heating

Abstract: Knowledge of single crystal and aggregate elastic moduli of materials at high temperature is important in the development of high-temperature structural ceramics as well as for other areas of material sciences Sound velocities, and hence elastic moduli, can be readily measured on micro-crystals, polycrystalline aggregates and amorphous materials using Brillouin scattering We have developed techniques for determining the elastic moduli at high temperatures, using both electric resistive heating (to 1800 K) and CO_2 laser heating (to T > 2500 K) The full set of elastic constants of transparent oxides at high temperatures can be measured on samples with dimensions of 100 × 100 × 20 μm or even smaller Compact resistance heaters of our design were used to study the temperature dependence of the elastic moduli of a variety of crystalline oxides and glasses, and can be used to observe high-temperature phase transitions involving elastic softening The combination of Brillouin scattering with CO_2 laser heating allows measurements of the elastic moduli of oxides at even higher temperatures, approaching the melting points of refractory materials The acoustic velocities of single-crystal MgO were measured to a maximum temperature exceeding 2500 ± 100 K Both Brillouin and Raman measurements were performed on CO_2 laser-heated samples of single-crystal α-Al_2O_3 to temperatures exceeding 2000 ± 100 K Our results show that Brillouin scattering coupled with CO_2 laser heating is a viable means of performing sound velocity measurements at temperatures significantly higher than those readily made using resistance heating