A.N. Durga Rani

Mixed glass former effect in mol% 66.67 AgI-24.66Ag2O-8.33((1−x)B2O3−xAs2O3) quaternary amorphous solid electrolytes

Fast ion conducting quaternary amorphous solid electrolytes with chemical composition in mol% 66.67 AgI-24.66Ag2O-8.33((1 - x) B2O3-xAs2O3) for 0.1 < × < 0.9 were investigated emphasizing the influence of two glass formers on their transport properties. X-ray diffraction and differential scanning calorimetry were utilized to determine the amorphous nature and the thermal stability of these amorphous solid electrolytes for solid state battery application. Ionic and electronic conductivity studies were performed on all the electrolyte compositions to evaluate the highest conducting composition. The presence of a second glass former in the quaternary amorphous network has shown a pronounced effect on the glass transition temperature of the electrolytes. This mixed glass former effect is discussed based on the ionic radius, field strength and the valence state of the glass forming oxide cation and its role in the formation of an amorphous network.

Mixed glass former effect in AgI-Ag2O-V2O5-P2O5 quaternary amorphous solid electrolytes

Abstract In the process of investigating electrical conduction in ternary and quaternary amorphous solid electrolytes, interesting results have been obtained in the AgI-Ag2O-V2O5-P2O5 quaternary system. The present investigation reports the mixed glass former effect on the ionic and electronic conductivities and glass transition temperatures of the electrolyte compositions mol% 66.67 AgI-22.22Ag2O-11.11((1−x)V2O5-xP2O5). A double maxima was observed in the ionic conductivity at x = 0.2 and 0.7 where the electronic conductivity assumes minimum values. The glass transition temperature was observed to increase with x in analogy with amorphous semiconducting (1−x)V2O5-xP2O5- oxides. These results are discussed on the basis of the entropy of mixing two glass formers and the possible structural changes that might occur in the quaternary amorphous network due to the presence of a second glass former. The observed properties are compared to the ternary amorphous systems AgI-Ag2O-V2O5 and AgI-Ag2O-P2O5 emphasising the mixed glass former effect in light of their covalency and field strength.

Influence of glass former to modifier ratio on the transport phenomena of glassy silver iodochromate solid electrolytes

Abstract Fast ionic conduction in the AgI-Ag 2 O-CrO 3 electrolyte system has been studied and the influence of glass former to glass modifier ratio on the conduction phenomena has been reported. These electrolytes have been characterised by X-ray diffraction, electrical and electronic conductivities, complex impedance, thermoelectric power and infrared absorption techniques. The possible structural changes occurring in the Ag 2 O-CrO 3 matrix on the variation of the glass former to modifier ratio have been discussed.

Characterisation of X(AgI) · (1−X)(Ag2CrO4) electrolytes by transport and structural properties

Abstract Fast ion conducting electrolytes in the system X(AgI) · (1− X)Ag2CrO4) for 0⩽x⩽100 mol% of AgI, have been characterised by X-ray diffraction, electrical and electronic conductivities, thermoelectric power and infrared absorption techniques. A high ionic conductivity of the order of 10−3 with low electronic conductivity has been observed for two electrolyte compositions for X=33.33 and 80 mol%. Infrared absorption studies have shown vibrational modes characteristic of CrO42− structural units.

Fast ion transport in silver vanadiumphosphate glasses

Investigation of the transport phenomena in silver vanadiumphosphate glasses has revealed that the observed fast ionic transport is due to silver ions. The glassy or amorphous nature of the materials has been confirmed and characterized by X-ray diffraction technique. Ionic conductivity measurements on compositions with mol% XAgI-(1-X) (2Ag2O-1(0.8V2O5-0.2P2O5) for 40<X<80 has led to the establishment of the highest ionic conducting composition as 70AgI-20Ag2O-10(0.8V2O5-0.2P2O5) in the entire system. Electronic conductivity measurements are performed on these compositions to determine the minority charge carriers and the magnitude of the electronic contribution to the total conductivity. Infrared absorption studies on these materials proved that the basic structural units in all the compositions are the same and the highest conducting composition has a large number of V2O5 and P2O5 polyhedral structures. The glass transition temperatures (Tgs) of all the compositions are established by recording the differential scanning calorimetric thermograms with indium as a reference material. The fast ion transport is explained invoking the weak electrolyte theory and the progressive decrease in Tg with increasing AgI content has been explained using the thermodynamic regular solution model applicable to silver halide systems. The composition mol% 70AgI−20Ag2O−10(0.8V2O5−0.2P2O5) has been found to exhibit the highest ionic conductivity of 8.2 × 10−2S/cm and a low electronic conductivity of 1.2 × 10−8S/cm at 25°C. Hence this composition can be utilised as a solid electrolyte in solid state ionic devices.

Transport studies on superionic AgI−Ag2O−CrO3 glasses

Glasses in the system x AgI-(1- x ) (Ag 2 O-2CrO 3 ) with 0≤ x ≤1 have been prepared and characterised by X-ray diffraction technique. Ionic and electronic conductivity studies have been carried out on all the samples in the glass forming region. On the best conducting composition, thermoelectric power studies have also been carried out. Transport number of silver ions has been found by EMF method. A typical galvanic cell was constructed with the highest conducting composition as the electrolyte and the variation of open circuit voltage with time was investigated.

Heat of transport and thermoelectric power studies in Agl-Ag2O-V2O5-P2O5 quaternary amorphous solid electrolyte system

From these experimental results, it is speculated that the silver ion transport in this system results in a «diffusion path» which is composed of I − ion polyhedra as in α-AgI. The probability of forming such diffusion paths is greater in quaternary amorphous solid electrolytes with the randomly and densely packed structure of the two glass formers than in ternary amorphous solid electrolytes, where only one glass former forms the macromolecular structure

Superionic conduction in the glassy AgI-Ag2O-CrO3 system: glass formation and infrared absorption studies

Abstract Superionic conduction in the amorphous AgI-Ag 2 O-CrO 3 electrolyte system has been studied. The glass-former-to-modifier ratio and the concentration of AgI were varied continuously to establish the glass-forming domain of the system. X-ray diffraction and differential scanning calorimetry were used as sensitive probes. Transport studies and infrared absorption spectroscopy were used to characterise xAgI -(100− x )( Ag 2 O - CrO 3 ) glasses to help clarify the conduction process and the possible structural units of these electrolytes.

Influence of disperoids on the transport behaviour of Ag2HgI4

The basic research on solid electrolytes was bifurcated into a search for new compounds that exhibit very high ionic conductivity at ambient temperature and to modify the properties of known materials as viable electrolytes at ambient temperature. The heterogeneous doping technique is used in the second category where the transport properties of an ionic solid can be modified by the dispersion of insoluble and insulating oxides as a second phase. Stimulated by the success of two orders of enhancement in the electrical conductivity of LiI by the dispersion of fine alumina particles [1], several other successful experimental results were reported (see [2-4] and references in [3, 4]). Eventually these dispersed solid electrolytes have attracted a great deal of attention to both experimental and theoretical researchers to understand the mechanism of enhancement in electrical conductivity of the host ionic solid. Silver tetra-iodomercurate is one of the earliestknown silver-ion conductors which possesses high silver-ion conduction only in the ol-phase above 60 °C. At ambient temperature it is a poor ionic conductor [5]. Hence, this study aimed at enhancing the ambient temperature conductivity of AgzHgI4, since it has been successful with its two constituents AgI [2] and HgI2 [6]. A new method of preparing these heterogeneous solid electrolytes was adapted and the validity of the method was tested on AgI electrolytes with various dispersoids, which is also correlated with a different documented method of preparation. The present investigation dealt with the discussion of experimental results on the influence of various dispersoids on the conduction characteristics of Ag2HgI4 in the low-conducting fiand highconducting 0l-phases. The compound AgI was precipitated from KI and AgNO3 (AR grade, BDH, UK) solutions followed by drying at 110 ° for 48 h under an inert atmosphere. Various insulating oxides of different particle sizes, 7-A1203 (0.06/~m), y-AI20 3 (1.0/~m) and SiO2 (0.007/~m) from Meller Company and polishing alumina (about 1.0/~m) from Geologists Syndicate, India were dispersed in the AgI matrix, by dispersing them in AgNO3 solution before precipitating AgI. Thus, the composite electrolytes ( 1 x) AgI-x dispersoid for 0 < x < 40 mol % (wt % in the case of polishing A1203) were precipitated and dried under vacuum at 110 °C for 48 h. In an earlier report [2] these AgI composite electrolytes were prepared by melting appropriate quantities of AgI and dispersoid under vacuum, followed by slow quenching. The compound AgzHgI 4 was synthesized from

Effect of dispersoids on the conduction characteristics of Ag2HgI4

Abstract The compound Ag2HgI4 has been synthesised from K2HgI4 and AgNO3 solutions. Various dispersoids of sub-micron particle size like alumina (0.06 μ), silica (0.0071 μ) and polishing alumina (800 mesh) have been dispersed into the Ag2HgI4 matrix. The dispersoids were added to AgNO3 solution and precipitated with K2HgI4 solution followed by vigorous stirring. The effect of dispersion on the conduction characteristics of Ag2HgI4 is reported.