J.J. Videau

Raman spectroscopic studies of fluorophosphate glasses

Some fluorophosphate glasses obtained by fluorination of NaPO3, xNaPO3−yAlF3 or tNaPO3−wAlF3−vCaF2 have been studied by Raman spectroscopy in VV and VH polarisations. The observed bands have been assigned by comparison with those vitreous NaPO3 and Na4P2O7, as well as crystallised K2PO3F and KPO2F2, and molten cryolite. Structural models are proposed for the various compositions. They are built up with arrangements of following species: (PO3)2n−n chains; (P2O7)4− dimers, (AlF6)3− octahedra, P(O, F)4, (AlF4)− and (AlOF3)2− tetrahedral groups. For glasses rich in phosphate −OPO2F− and −OPOF2 terminal groups are displayed; the latter being favoured for a higher fluorine concentration.

EPR of transition metal ions (Mn2+, Cu2+, Cr3+, Fe3+) in fluoroaluminate glasses

Abstract EPR experiments have been performed on glasses related to the CaF2BaF2AlF3 system. Fluctuations of the EPR parameters are observed in the case of divalent ions which occupy distorted sites. The trivalent ions occupy sites of “fully rhombic” symmetry. A comparison with the EPR parameters obtained for crystallized α-CaAlF5 leads to the conclusion that the glass is built up by random type chains containing aluminium separated in various ways by the divalent cations, the coordination numbers of which may differ.

Structural approach of the (xPbCl2-(1−x)Sb2O3) glass system

A structural approach of xPbCl2, (1 − x)Sb2O3 glasses, quenched from the melt, is proposed. The crystallization process of the glasses is analyzed and a Raman scattering investigation is reported. The two investigations give valuable information on the structural arrangement of the glass network. Observations within the xPbCl2, (1 − x)Sb2O3 system show variations of local structure and a comparison is made with previously reported data for some Sb or As based glasses.

New oxyhalide glasses involving Sb2O3

Abstract A family of oxyhalide glasses involving Sb 2 O 3 and various R m X n halides (R = monovalent or divalent cation; X = F, Cl, Br or I) has been prepared. The thermal, mechanical and optical properties of the glasses are reported. Easy to prepare and to shape (windows, fibers,), chemically stable, they are transparent from about 0.43 μm up to 6.50 μm. The special case of vitreous Sb 2 O 3 is also discussed.

Glass formation and conductivity in the AgIAgO0.5TeO2 system

Abstract A large glass-forming area has been identified in the AgIAgO 0.5 TeO 2 system. Thermal properties have been determined as a function of AgI content. The ionic conductivity has been studied as a function of the Ag + concentration. In these TeO 2 glasses, infrared spectroscopy shows that a part only of Ag + ions contributes to the ionic conduction as in the AgIAg 2 OM x O y glasses, where M x O y represents B 2 O 3 or P 2 O 5 .

Investigation by raman scattering of the [TeO2−RMO0.5] (M = Ag or Tl) glasses and of the related ionic conductors [TeO2−RMO0.5]1−x)[AgI]x

Abstract The structure of binary glasses [TeO 2 − R MO 0.5 ], with M = Tl (or Ag) and 0.22 ⪯ R ⪯ 1 (0.28 ⪯ R ⪯ 1) has been investigated by Raman scattering under VV and VH polarizations. The two systems behave in nearly the same way: in the tellurite-rich part, the structure is built up of [TeO 4 ] trigonal pyramids, a disordered form of the paratellurite α-TeO 2 . With increasing R between 0.40 (0.35) and 1 (the upper R value limiting the vitreous domain in each system), an increasing proportion of tri-coordinated tellurium [TeO 3 ] is formed in the glasses. The ternary [TeO 2 − R MO 0.5 ] (1− x ) [ AgI ] x glasses have been reported as ionic conductors. The structure of the tellurite network is not modified by the addition of silver iodide. A band appearing in the low-energy part of the Raman spectra is assigned to vibrations of [AgI 4 ] species.

Thermal properties and surface reactivity in simulated body fluid of new strontium ion-containing phosphate glasses

In this paper, we investigate the effect of SrO substitution for CaO in 50P2O5–10Na2–(40−x)CaO–xSrO glass system (x from 0 to 40) on the thermal and structural properties and also on the glass reactivity in simulated body fluid (SBF) in order to find new glass candidates for biomedical glass fibers. The addition of SrO at the expense of CaO seems to restrain the leaching of phosphate ions in the solution limiting the reduction of the solution pH. We observed the formation of an apatite layer at the surface of the glasses when in contact with SBF. SrO and MgO were found in the apatite layer of the strontium ion-containing glasses, the concentration of which increases with an increase of SrO content. We think that it is the presence of MgO and SrO in the layer which limits the leaching of phosphate in the solution and thus the glass dissolution in SBF.

Glass formation and conductivity in the Ag2SAgPO3 system: Evidence against cluster pathway mechanisms for high ionic conductivity

Abstract The glassforming region in the system Ag 2 SAgPO 3 has been determined and studies of electrical conductivity, infrared absorption, thermal expansion and transport number of Ag + ions have been made. The results of the electrical conductivity and the transport number measurements show that the conduction is essentially ionic in nature and due to silver ions alone. In this system, as in AgIAgPO 3 , the logarithm of the ionic conductivity increases linearly with increasing Ag 2 S mole fraction and extrapolates to the value of the superionic crystalline Ag 2 S. However, an explanation similar to the α-AgI cluster pathway model proposed for AgI-containing systems is not tenable since IR spectra show that Ag 2 S dissolves by an acid-base chemical ordering process to give shorter phosphate chain structures which approach the pyrophosphate stoichiometry at the glassforming limit.

Sodium-iron fluorophosphate glasses: Part 2: EPR and mössbauer resonance study

Abstract EPR and Mossbauer measurements have been performed on sodium-iron fluorophosphate glasses. Mossbauer spectra show the presence of Fe 3+ and Fe 2+ both in octahedral coordination sites. However, for low iron concentration, EPR suggests a small number of Fe 3+ tetrahedra coexisting with Fe 3+ octahedra. On the basis of these results, Fe 3+ tetrahedrally and/or octahedrally coordinated, connected with P(O, F) 4 tetrahedra would behave as a network-former cation, whereas Fe 2+ would substitute for Na + as a netweork-modifier. Long range magnetic order previously observed by magnetic measurements has been confirmed for iron-rich compositions.

Ionic conductivity and structure of thallium tellurite glasses containing AgI

The ionic conductivities of [TeO2:RTlO0.5](1−x)[AgI](x) glasses have been determined and compared with those of compositions [TeO2:RAgO0.5](1−x)[AgI](x). The conductivity increases when xrmAgI increases, but lower conductivities are observed for glasses based on thallium tellurite than for those based on silver tellurite. It is concluded from the conductivity variation with the glass composition that the ionic conductivity properties are bound essentially to the mobility of the Ag+ ions located in an iodide environment. The IR and Raman spectra of ternary [TeO2:RTlO0.5](1−x)[AgI](x) glasses show only small modifications of the tellurite network, irrespective of the amount of AgI introduced into the binary glasses. The existence of intermediate-range order in these materials is discussed.