The dynamic shear modulus and compliance of the dynamic glass transition wereinvestigated in two metallic glasses (Pd_(40)Ni_(40)P_(20) and Zr_(65)Al_(7.5)Cu_(17.5)Ni_(10).Isothermal measurements over four frequency decades enable the determination of shape parameters forthe proper glass transition. The real part of the dynamic shear compliance shows a step height ofapproximately a factor of 2.6 for Pd_(40)Ni_(40)P_(20), comparable to low molecular weight glassformers or the segmental mode as part of the glass transition in high molecular weight polymers. Thefrequency dependence of the imaginary part of the shear compliance at the high frequency side ofthe peak shows an exponent near the Andrade value of 1/3.
K. Schroter G. Wilde R. Willnecker M. Weiss K. Samwer E. Donth
Using frequency and temerpautre-depenent conductivity data for x AgI · (1-x) AgPO//3 glassess in he compsoition k range form kx = 0.10 to x = 0.55, we find that the number density fo mboile ions as wel as the ionci relaxation emchanism are independent of tmeperature and compsoition. We belveve that this result si important in roder to clarify the contrversial ole f AgI for the ion transport in these glasses. Mloreover, ur observation should gerally impact on he understanding fo fast ion codncution in glass. In kthe freqency range convered in korur sudy, i. e., at freqenceis belwo a few MHz a sueprlinear dependence of the condcutivity on freqency as reproted recently has not been observed.
Roling, B. Ingram, M. D.
no.10
Framework aluminosilicate glasses with varying charge-balancing cation (Li, Na, K, Rb and Cs) have been studied with **2**7Al and **2**9Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and **2**7Al on-resonance and off- resonance nutation NMR spectroscopy. This first application of off-resonance nutation NMR to disordered samples proves that it is a promising technique for the determination of mean quadrupole interactions in amorphous systems. Linewidths for Al decrease systematically with increasing size of the cation, due to a decrease in the quadrupole interaction from 5.0 MHz for the Li glass to 2.8 MHz for the Cs glass. A simple point-charge model effectively predicts the decrease in the quadrupole interaction. This indicates that the alkali ion is located close to aluminum. Looking at the residual linewidth after subtraction of the quadrupole broadening, the Al chemical shift distribution does not change significantly with the type of alkali ion. The same is true for the observed Si linewidth. (Author abstract) 46 Refs.
Dirken, P.J. Nachtegaal, G.H. Kentgens, A.P.M.
no.10
It is known that W5+, Mo5+, and Fe3+ ions are sensitive indicators for thestructural changes of the local symmetry in oxide glasses. Thus, these centres were used as EPRprobes in P2O5-A(2)MO(4)-A(2)O (M=Mo, W and A=Li, Na). The M5+ ions are located in a distortedenvironment. Their symmetry is lowered as A(2)O content is high. In iron-dopped glasses Fe3+ centresoccupy distorted octahedra. The distortion extent is less than 7%. Radiation-induced defects havebeen detected, it is concerned with a PO42- centre and peroxy radicals.
Boudlich D. Archidi ME. Haddad M. Nadiri A. Berger R. Yahiaoui EM.
A theory of weakly nonlienar low-temperture relaxational absorption f acosutic and electromagnetic wdaves in dielectric and metallic glasses isdevleoped. Basedupon te mdoel fo two-level tuneling systems we sdhwo that the nonienar contriubtion to the adbsorption k can be anomalously large. Tis is the case at wo enough frequencies, ωτ//0(T)<<1, where τ//0(T) is the miniml relaxation tiemf fortwo-level systems with te itnelrevel splitting ～k//BT. in dielectric glasses, the lwoest-roder noninear contribution is proportional to the wave’s intenstiy. It i negativ eand exhbitis anomalous frequency and tmeruatre dependenes, ΔΓ/Γ//0∝[ωτ//0(T)]^-1/2 T^-2. in metallic glasses, the nonienar contribution is also negative, and it i proportional to the square root of the wav’es intensity and independent of the frequency. Nuemrical estiamtes shwo that the rpedicted nonlienar conribution can be measured experiemtnally.
Kirkengen, M. Galperin, Yu. M.
Third-order nonlinear susceptibility ( vertical bar chi **(**3**) vertical bar ) and photoluminescence fast decay time ( tau PL) of phosphate glasses doped with a high amount of CdS, CdSe and CdTe microcrystallites has been measured. In the case of CdSe-doped glasses, vertical bar chi **(**3**) vertical bar increased in proportion to the volume fraction of CdSe microcrystallities. However, vertical bar chi **(**3**) vertical bar / alpha ( alpha : absorption coefficient), tau PL and vertical bar chi **(**3**) vertical bar /( alpha tau PL) was almost constant for the higher amounts of CdSe microcrystallites. On the other hand, vertical bar chi **(**3**) vertical bar /( alpha tau PL) increased with decrease of microcrystallite size. It was emphasized that vertical bar chi **(**3**) vertical bar /( alpha tau PL) was dependent on quality of microcrystallite. In this study. CdS-doped glasses exhibited excellent nonlinear properties. vertical bar chi **(**3**) vertical bar /( alpha tau PL) and tau PL of CdS-doped glasses reached to 6 esu center dot cm/s and 150 ps, respectively. (Author abstract) 11 Refs.
Omi, S. Hata, C. Uchida, K. Kaneko, S. Tanji, H. Asahara, Y.
The origin of optical non-linear response has been investigated in titaniumand niobium borophosphate glasses and in tellurite glasses. Correlations between the local structureof polarizable entities within the glasses and their optical activities have been tentativelyestablished through a semi-empirical model and ab-initio calculations.
Fargin E. Cardinal T. Videau JJ. Villesuzzanne A. Le Flem G. Berthereau A.
The fluorescence spectra of 9-anthrol during the sol-gel-xerogel transitions of 13 systems containing different silicon and aluminum ratios and catalysts have been observed at a constant temperature (300 K) as a function of the sol-gel reaction time. Fluorescence decay curves for typical xerogel samples also have been observed. 9-Anthrol in the sol-gel systems showed four different fluorescence bands originating from the hydrogen-bonded, the complex, the ion pair, and the anion form species. Continuous light irradiation of the xerogels at 360 nm led to an increase in the fluorescence at 480 nm. These findings indicate that anthrone transforms to 9-anthrol by the photoinduced intermolecular proton transfer in these matrixes. The most effective and remarkable tautomerization occurred in the Si:Al equals 90:10 system, and it was concluded that this photochromic behavior occurs by the photoinduced proton transfer from a proton at the surface Bronsted acid site on the-O-Si-O-Al-O- network to the anthrone molecule. (Author abstract) 39 Refs.
Fujii, Tsuneo Kodaira, Kazuhiko Kawauchi, Osamu Tanaka, Nobuaki Yamashita, Hiromi Anpo, Masakazu
We present the experimental results on the effects of hydrogen doping on the superconducting and paramagnetic properties of zirconium-rich (x > 0.66) Zrx3d1-x metallic glasses. Zr0.70Cu0.30, Zr0.67Ni0.33 and Zr0.67Co0.33 are superconductors with a superconducting transition temperature in the vicinity of 2 K, while Zr0.68Fe0.32 is a paramagnet down to very low temperatures because of pronounced spin-fluctuations. The magnetoresistivity data are analysed using theoretical models of weak location and electron-electron interactions. Doping with hydrogen reduces the superconducting transition temperature in Zr0.70Cu0.30, Zr0.67Ni0.33 and Zr0.67Co0.33 metallic glasses. The magnetoresistivity enhancement of hydrogen-doped Zr0.68Fe0.32 has been attributed to the increase of the Stoner factor, (1-I)^-1. That increase indicates an enhancement of spin fluctuations with hydrogen.
IVAN KOKANOVI BORAN LEONTI JAGODA LUKATELA
We use the negative replica method, which was originally developed for thestudy of overfrustation in disordered systems, to investigate the statistical behavior of the costfunction of minimax games. These games are treated as hierarchical statistical mechanical systems,in which one of the components is at negative temperature. [References: 13]
Varga P.
