J. Portier

Glass formation and conductivity in the AgIAgO0.5TeO2 system

Abstract A large glass-forming area has been identified in the AgIue5f8AgO 0.5 ue5f8TeO 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 AgIue5f8Ag 2 Oue5f8M 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.

Raman scattering in tellurium-metal oxyde glasses

Abstract Structural studies were undertaken of glasses in the (1−x)TeO 2 − xZnO system. The glass domain (0,09 x > 0,40) was verified and variations observed in the Raman spectra were correlated with changes induced on the TeO 2 polyhedra upon glass formation with the addition of the metal oxyde. Spectra were recorded as these glasses were heated through T C and recrystallized. The spectral profiles observed in the recrystallized systems closely resemble those of the broad bands in the initial glasses. The sharp bands in the final spectra, characteristic of a more ordered phase, are interpreted (by correlation with neutron diffraction data) on the basis of chains of TeO 3 ue5f8TeO 4 polyhedra interlaced with chains of ZnO 6 groups.

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 Sue5f8AgPO 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 AgIue5f8AgPO 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.

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.

Transport properties of rapidly quenched glasses in the Z2S3−Ag2S−AgI (Z=As, Sb) systems

Study of electrical properties of glasses investigated in the Z 2 S 3 −Ag 2 S and Z 2 S 3 −AgI (Z=As, Sb) binary systems has shown that the best performance should be obtained for materials involving a high silver sulfide content for glass stability and a high silver iodide content for high silver mobility. Consequently we have undertaken the research of new glasses involving at the same time high silver sulfide and silver iodide contents. For it we have used the twin-roller quenching technique which allows generally to enlarge notably the vitreous domains. Wide glassy domains have been shown in the As 2 S 3 −Ag 2 S−AgI and Sb 2 S 3 −Ag 2 S−AgI systems. The isolated materials have been characterized and transport properties have been studied as a function of their composition. The best conductivities are obtained for glasses involving the lowest As 2 S 3 or Sb 2 S 3 content and a composition close to Ag 3 SI: 0.03As 2 S 3 −0.47Ag 2 S−0.50AgI: σ 25°C ≈2×10 −2 Ω −1 , cm −1 , E =0.16 eV, 0.03Sb 2 S 3 −0.57Ag 2 S−0.40AgI: σ 25°C ≈6×10 −2 Ω −1 cm −1 , E =0.15 eV. The transport number measurements show that the glasses are essentially ionic conductors (0.991–0.998 as determined by an EMF method). Using the triangular voltammetry the redox stability domain has been determined, it is about 2 V for a current density of 0.1 mA/cm 2 . The influence on the transport properties of the introduction of AgI into sulfide glasses has been studied by plotting log σ 25°C and Δ E σ for different glasses (Z 2 S 3 − p Ag 2 S) t−y (AgI) y (Z=As, Sb) as a function of y ( p =fixed). It must be noted that the variation of log σ and E σ with y for the (Z 2 S 3 − p Ag 2 S) 1− y (AgI) y glasses is linear only for some particular values of p (1 p y ( y 0.50). Results obtained for low and high values of p ( p p >2) show that such a behavior depends essentially on the p parameter. A glass model structure has been proposed on the basis of the infrared spectra. In particular the results suggest that the structure of the glasses of composition close to Ag 3 SI is related to the high temperature froms of the silver iodide and the silver sulfide which give moreover solid solution on the sulfide side.

Raman studies of recrystallized glasses in the binary TeO2PbO system

Abstract The Raman spectra of binary TeO 2 ue5f8PbO glasses were recorded as the systems were heated through their T g and T c temperatures. In every case, a subsequent recooling resulted in recrystallization. The spectral profile observed in the case of the recrystallized glasses was nearly identical to the contour of broad bands in the spectra of the original glasses. The sharp bands in the recrystallized systems, characteristics of a more ordered phase, were interpreted on the basis of a structure of chains of TeO 3 and TeO 4 groups interlaced with infinite chains of PbO 6 octahedra. As the coordination of the polyhedra of various cations in glass systems should be maintained during crystallization, the analysis of the recrystallized systems yielded the basis for a model of the parent glasses.

Role of the mineral binder in the sensing properties of screen-printed layers of semiconductor oxides Sr1−yCayFeO3−x (0 ⩽ y ⩽ 1; 0.19 ⩽ x ⩽ 0.50)

Abstract The sensitivity to methane of layers of semiconductor oxides Sr 1− y Ca y FeO 3− x (0 ⩽ y ⩽ 1, 0.19 ⩽ x ⩽ 0.50), screen-printed with CaO/B 2 O 3 /Al 2 O 3 /SiO 2 or SrO/B 2 O 3 /Al 2 O 3 /SiO 2 as insulating mineral glassy binder, has been shown to increase smoothly up to volumetric concentrations of binder of about 30%, then very sharply between 30 and 40%. Above this concentration, the sensitivity reaches a maximum and finally tends to decrease. Conversely, the resistances of the layers steadily increase with the concentration of binder. A tentative interpretation to explain the variations of sensitivity and resistance of the layers with the binder content has been proposed. The interpretation is based on the formation of a thin gas-sensitive shell around the grains of semiconductor oxide after the liquid binder has first filled the empty spaces between these grains during sintering.

Influence of the S2− = 2l− substitution on the ionic conductionproperties of the Ag+ glasses inside the AgPO3-Ag2S-AgI system

Abstract The glass forming region in the AgPO3-Ag2S-AgI system has been determined and some physical chemical properties including thermal behavior, ionic conductivity, transport number, and infrared absorption have been investigated. The results of the electrical properties and the transport number measurements show that the conduction is essentially ionic in nature and due to silver ions alone. The study of the influence of the replacement of 2I− by S2− on the electrical properties of glasses of formulation (AgS0.5)α(AgI)β(AgPO3)γ (α + β + γy = 1) exhibits a quasi-linear variation of log σ25°C with the ratio r [r = AgS0.5/(AgS0.5 + AgI) = α/(α + β)] at fixed values of γ. A comparative investigation of the electrical properties of the glasses P2O5-Ag2O-AgI and P2O5-Ag2O-Ag2S-AgI shows that these materials belong to the same family of glasses. An identical limit seems to be obtained when γAgI ∼- 0.67, independent of the nature of Ag2X(X = O, S), either Ag2O or (Ag2O + Ag2S), and of the value of p, for the glasses of formulation [P2O5 - p(Ag2O + Ag2S)]1−γ[AgI]γ.

Approche structurale par spectroscopie d'absorption infrarouge de verres thiohalogenes d'antimoine

Abstract A structural approach of Sb2S3ue5f8SbBr3ue5f8SbI3 and Sb2S3ue5f8PbBr2ue5f8PbI2 glass systems is suggested on the basis of infrared absorption investigations. The glasses are built up with SbS3 pyramids more or less polymerized and connected to various thiohalide antimony or lead entities. A correlation between structure and optical properties is proposed for the Sb2S3ue5f8PbBr2ue5f8PbI2 glasses.