AgI Content Research Articles

Mechanical behaviour of thin As-S-AgI films for sensor applications

The mechanical behaviour of chalcogenide thin films is of great importance for a variety of applications. The requirements for homogeneity, uniformity, surface smoothness, excellent adhesive strength and minimal residual stress are decisive for the technological performance of thin films in the field of optical and sensor devices. Thin films from the system have been prepared by vacuum thermal evaporation from the corresponding bulk glasses. The film structure and surface morphology have been studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The investigated chalcogenide films are amorphous as revealed by XRD, featureless and with smooth surfaces viewed from the AFM pictures. The stress measurements of the thin films deposited on silicon cantilevers have been carried out by cantilever bending technique. The results obtained have been discussed with respect to the film composition and structure. The change of the stress from tensile to compressive registered in the films with AgI content higher than 15 mol. % could be explained with structural transformations.

Small angle neutron scattering experiments on solid electrolyte (AgI) x (AgPO3)1−x

Superionic conductor glasses have generated considerable technological interest in the applications such as batteries, fuel cell, sensors, etc. In AgPO3 glass doped by AgI, (AgI) x (AgPO3)1−x , small size of AgI clusters were formed and dispersed in the AgPO3 glass. The size of clusters in the sample depends on the AgI content and influences the electrical properties of the sample. To understand the microscopic structure, in particular the shape and size of the clusters, a series of small angle neutron scattering experiment on (AgI) x (AgPO3) x with x = 0.0, 0.5, and 0.7 were performed at the Neutron Scattering Laboratory–National Nuclear Energy Agency, Indonesia. By assuming the clusters are spherical, a radius of gyration R g of the clusters was determined from a Guinier plot. As there are different clusters sizes in the samples, a polydisperse model is also used to analyze the data. The results show that the average radius of clusters dispersed in (AgI) x (AgPO3)1−x samples with x = 0.0, 0.5, and 0.7 are around 236.2, 252.6, and 257.5 A, respectively.

Conductivity and structure of a polyamide/silver iodide nanocomposite

AbstractIn this study, the structure and properties of an organic–inorganic composite material prepared from nylon 6 doped with fine particles of silver iodide (AgI) were examined. The preparation of the composite involved the complexation of nylon 6 with polyiodide ions such as I and I by immersion in an iodine/potassium iodide (I2–KI) aqueous solution followed by reaction in a silver nitrate (AgNO3) aqueous solution; this resulted in the in situ formation of β‐AgI fine particles within the nylon 6 matrix. The AgI content formed in the composite was dependent on the immersion temperatures of the I2–KI and AgNO3 solutions. Lower solution temperatures resulted in larger amounts of AgI in the composite. This method readily provided a composite with a high content of AgI in nylon 6 and a conductivity of approximately 10−5 Ω−1 cm−1. In a uniaxially oriented nylon 6 matrix, AgI particles precipitated with anisotropic shape, which was caused by the orientation of the precursor polyiodide ions. The structure of the oriented composite provided the anisotropic conductivity. Additionally, the composite exhibited high antibacterial properties. The procedure used in this study is considered a unique method for the preparation of organic–inorganic composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Electrical properties and microstructure of glassy-crystalline Ag +-ion conducting composites synthesized by a high-pressure method

Rigid, mechanically reinforced, composite Ag +-ion conductors based on xAgI·(100- x) (0.67Ag 2O·0.33B 2O 3), 40 ≤ x ≤ 60, glasses and hard insulating powders of α-Al 2O 3 (2 µm) or ZrO 2 (1 µm) were prepared by a high-pressure method. Microstructure of the composites, depended on the content of AgI in the glasses and the temperature of the high-pressure stage of the synthesis. In all cases, however, it consisted of the evenly distributed phases (conductive and insulating), which did not interpenetrate at a nanometer length scale. It was found that the high electrical conductivity of the composites, though somewhat lower than that of the glasses, generally followed the temperature- and composition dependencies of the latter. An important advantage of the composites over the corresponding glasses was their higher microhardness and non-brittleness, which, contrary to the glasses, enabled their post-synthesis machining, cutting or polishing.

Correlation of ion dynamics and structure of superionic tellurite glasses

Ion dynamics and structure of a series of superionic AgI-doped silver tellurite glasses have been investigated in this paper. The composition dependence of the dc conductivity and the activation energy of these glasses has been compared with those of AgI-doped silver phosphate and borate glasses. We have observed that the conductivity increases and the activation energy decreases with increase of AgI content and that the tellurite glasses have higher conductivity than those for phosphate or borate glasses. We have analyzed the ac electrical data in the framework of the power law and the electric modulus formalisms. We have established a correlation between the crossover rate of the mobile silver ions and the rearrangement of the structural units in tellurite glasses. The scaling of the conductivity spectra has been used to interpret the temperature and composition dependence of the relaxation dynamics. Analysis of the dielectric relaxation in the framework of modulus formalism indicates an increase in the ion-ion cooperation in the glass compositions with increasing AgI content.

Preparation, characterization, and optical properties of host–guest nanocomposite material SBA-15/AgI

Host–guest nanocomposite SBA-15/silver iodide (AgI) was prepared by heat diffusion method. The structure, composition and optical properties of such material were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, energy disperse spectroscopy, electron paramagnetic resonance, diffuse UV–vis reflectance spectra, and photoluminescence (PL) spectra. When AgI content is below ∼15 wt%, the guest AgI is highly dispersed on the silica channel wall, and no longer exists in the crystalline state; when AgI content exceeds this value, AgI nano-crystal can be observed. A blue shift of ∼30 nm on the absorption edge as well as the formation of a band tail is observed. Besides, Ag clusters have been shown to exist in the composite. After the loading of guest AgI, the PL from silica at 330 nm can hardly be observed, and a novel PL emission located at 620 nm is found. The emission at 620 nm may be due to the transition process between the excited state of Ag clusters and the hole–trap state on the surface of AgI.

Novel chalcohalide glasses from the Ge–S–AgI system and some physicochemical features

Novel bulk glassy samples of the pseudoternary chalcohalide Ge–S–AgI system have been prepared. Glasses have been obtained by monotemperature synthesis in evacuated ampoules and standard melt-quenching technique. The glass-forming region in the system determined by X-ray diffraction is situated in the S-rich region on the Ge–S side (S/Ge = 1.2, 1.5, 2 and 3) with AgI content up to 20 mol.%. Some physicochemical properties of the amorphous materials and their compositional dependence have been investigated. In addition, the theoretical average coordination number (Z), the total constraints per atom (Nco), the radial (Na) and axial (Nb) strength of the bonds have been calculated and related to the experimental results.

Micro Raman, FT-IR/PAS, XRD and SEM studies on glassy and partly crystalline silver phosphate ionic conductors

Glassy and glassy-crystalline silver ion conductors of the AgI–Ag 2O–P 2O 5 system have been studied by FTIR-PAS and Micro Raman spectroscopies in conjunction with X-ray diffractometry, scanning electron microscopy and differential scanning calorimetry. It was found out that materials with lower (≤60 mol%) AgI contents are fully amorphous, while those with higher contents of AgI (>70 mol%) contain crystalline grains of β/γ-AgI embedded in the glassy matrix. Annealing of the glasses at 105 °C and/or 145 °C resulted in an increase in the formation of a yet unidentified crystalline phase dispersed in the glass. From the spectroscopic studies it was found that PO 4 3− units existed as separated species in the glass network or precipitated crystalline phases regardless the thermal treatment of the material. Vibrations of PO 4 3− units appeared to be affected by the total concentration of AgI and microstructure. The spectroscopic methods were also used to study crystallization process in the glassy samples.

Appearance of fast ionic conduction in AgI-doped chalcogenide glass powders prepared by mechanical milling

(AgI) x (As 2Se 3) 1− x glass powders were successfully obtained up to 70 mol% AgI content by the mechanical milling method. Electrical conductivities, which show the exponential increase with addition of AgI, are comparable to the values of the corresponding melt-quenched glasses. The conductivity of 60 mol% AgI-doped glass shows great increase at the early period of the milling. A DSC signal for the β–α phases transition of crystalline AgI becomes weak at the medium stage of the milling, whereas glass transition appears clearly. EXAFS measurements at Ag, I, As, and Se K-edges have been carried out for (AgI) 0.6(As 2Se 3) 0.4 glasses with different period of the milling. The amorphization process of (AgI) 0.6(As 2Se 3) 0.4 system was accompanied by a decrease of the nearest neighboring coordination number of Ag at the medium stage of the milling. These results suggest that the structural disordering of AgI units in the glass matrix would be strongly related to the appearance of fast ionic conduction.

Crystalline forms of silver iodide II: Determination of phase transformations

In order to obtain appropriate forms of AgI (?- and ?-), a procedure was developed to synthesize AgI at room temperature (23?C), whereby samples of varying crystallographic purity and of varying crystallographic contents of the different forms were obtained. This paper presents the results of investigations of the influence of the manner of preparation of ?-AgI and ?-AgI samples and the sample heating rate on the phase transformations and their temperatures. During the heating of non-ground, ground and pressed synthesized AgI samples, the phase transformations and the corresponding temperatures for one ?-AgI and four ?-AgI samples with different ?-AgI contents (representing a crystallographic impurity) were identified. The following phase transformations were observed for the non-ground AgI samples: ?-AgI ? ?-AgI at 149.6?C (for the ?-AgI sample) and ?-AgI ? ?-AgI at 148.7?C or 148.2?C for the ?-AgI samples with a minimum content of ?-AgI (less than 7 %), as a crystallographic impurity. The phase transition ?-AgI ? ?-AgI was irreversible because ?-AgI was obtained whenever the samples were heated up to 260?C. Manual sample grinding, as well as pressing at p1 = 650 MPa and p2 = 900 MPa resulted in the ?-AgI ? ?-AgI phase transition in all the investigated cases. .

Some features of chalcohalide glassy Ge–S–AgI thin films

Novel amorphous bulk materials from the chalcohalide Ge–S–AgI system were synthesized. From the as-prepared materials, thin amorphous films were evaporated by conventional thermal evaporation in vacuum onto different substrates. The amorphous nature of the bulk and layered materials was proved using X-ray diffraction. The morphology and uniformity of the deposited layers were investigated using scanning electron microscopy; the surface topology and roughness were studied by atomic force microscopy. The compositional dependence of the microhardness of the studied thin chalcohalide coatings was established and the influence of the third component (AgI) was determined. Stress measurements of the thin films deposited on special silicon cantilevers were performed in a period of 3 months and the relation between AgI content and stress was defined. In addition, the compositional dependence of the stress relaxation of the studied glassy Ge–S–AgI coatings was elucidated and the most probable reasons for the stress formation were proposed.

Composite Materials of Synthetic Mordenite and AgI

Composite materials made up of silver iodide and synthetic mordenite in sodium Na-MD or potassium form K-MD have been prepared by sintering a mixture of silver iodide and Na-MD or K-MD, by modified way of preparation. The prepared composites Na-MD/AgI and K-MD/AgI were characterised by X-ray powder diffractometry and thermal analysis. By integrating certain X-ray peaks quantitative reaction values were obtained. The composite Na-MD/AgI with 19 wt% of AgI content was also characterised by EDS analysis and ac conductivity measurements.

Thermochemical properties of composites of synthetic zeolite ZSM5 and silver iodide

Thermochemical properties of two kinds of composite material of synthetic zeolite ZSM5 in potassium form (K-ZSM5) with AgI have been studied. The composites have been prepared by treating the silver form of synthetic zeolite ZSM5 (Ag-ZSM5) with potassium iodide solution under different experimental conditions. One of the composites was additionally sintered at temperature 500°C for 20 h. Both composites have been characterized by TG, DTG, DTA, EDS analysis, X-ray powder diffractometry and X-ray photoelectron spectroscopy. The methods of thermal analysis as well as X-ray powder diffractometry and XPS confirmed the differences between the two composites caused by sintering during the synthesis. The content of AgI in the surface layer was different. No changes of the zeolitic mineral dimensions are observed.

Transport properties of AgI doped silver molybdate superionic glass-nanocomposites

We have reported the dc conductivity as well as the ac conductivity in the frequency range 10 Hz–2 MHzfor xAgI–(1−x)(0.5Ag2O–0.5MoO3), glass-nanocomposites in the temperature range 100–303 K. We have compared theconductivity and its activation energy for the molybdate nanocomposites withthose of the borate and phosphate glasses. We have analysed the ac conductivityusing the power law model. We have observed that both the dc conductivity andthe crossover frequency obtained from the power law model show an activatedbehaviour. We have also observed that the power law exponent is almostindependent of AgI doping content. Furthermore, the concentration of the mobileAg+ ions is found to be independent of temperature as well as the AgI content in thecompositions.

Effect of nanocrystallization on electrical conductivity of glasses and composites of the AgI–Ag 2O–B 2O 3 system

Amorphous and glassy–crystalline samples of the AgI–Ag 2O–B 2O 3 system with high content of AgI were prepared. It was shown that annealing of initially amorphous samples (with AgI content not higher than 60 mol%) leads to formation of crystalline grains of β-and γ-AgI and to a conductivity increase to 1.1·10 − 2 S cm − 1 at 20 °C (for AgI content of 55 mol%). The conductivity enhancement was attributed to interfacial regions surrounding crystalline grains. As-received samples with higher contents of AgI (≥ 75 mol% AgI) have high concentration of crystalline grains, mainly of AgI. The temperature dependence of conductivity undergoes step-like changes (close to 150 °C on heating and close to 120 °C on cooling). These changes are a consequence of the β-α-AgI phase transitions taking place in the crystallites.

Relaxation of silver ions in fast ion conducting molybdate glasses

The conductivity relaxation in the frequency range from 10 Hz to 2 MHz and in the temperature range from 108 to 303 K for the fast ion conducting AgI–Ag 2O–MoO 3 glasses has been reported. It has been observed that the conductivity relaxation in these glasses is highly non-exponential and that the conductivity relaxation mechanism is independent of temperature but is dependent on composition. It has been further observed that the motion of Ag + ions is decoupled more and more from the viscous motion of the glassy matrix with the increase of AgI content in the composition, giving rise to the increase of the conductivity.

Conductivity spectra in fast ion conducting glasses: Mobile ions contributing to transport process

In this Brief Report, we have investigated the conductivity spectra at different temperatures for the model glasses ${(\mathrm{Ag}\mathrm{I})}_{x}\ensuremath{-}{(\mathrm{Ag}\mathrm{P}{\mathrm{O}}_{3})}_{(1\ensuremath{-}x)}$, $0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.6$ and estimated mobile ${\mathrm{Ag}}^{+}$ ions contributing to the transport process. We have shown that a fraction of the total ${\mathrm{Ag}}^{+}$ ions contribute to the transport process. We have further observed that the fraction of ${\mathrm{Ag}}^{+}$ ions contributing to the transport process is independent of temperature as well as the AgI content. The mobility of ${\mathrm{Ag}}^{+}$ ions increases, leading to an enhancement of the conductivity due to AgI doping. These results are highly important in order to reveal the role of AgI for ion transport in fast ion conducting glasses.

Structural investigation of superionic AgI-containing orthoborate glasses

The structure of superionic glasses of the orthoborate composition xAgI-(1−x)[0.75Ag2O–0.25B2O3], 0.6⩽x⩽0.9, was investigated by infrared spectroscopy. Transmittance measurements were performed in the range of 30–5000cm−1 on freestanding flakes prepared by the twin-roller rapid quenching technique. Spectral analysis in the mid infrared revealed a network structure involving trigonal borate units (pyroborate, B2O54-, and orthoborate, BO33-) and various tetrahedral borate units, resulting from isomerization and disproportionation chemical equilibria. Addition of AgI to the borate matrix was found to affect the relative abundance of the borate units in favor of BO33- species. The analysis of the far infrared profiles showed that silver ions occupy oxide and iodide sites, without excluding the presence of mixed oxyiodide sites. The band associated with iodide sites, at ca. 100cm−1, was found to increase in relative intensity with AgI content and to acquire progressively characteristics resembling those of crystalline AgI for compositions x>0.78.

Structural and optical studies on mesoscopic defect structure in highly conductive AgI–ZnO composites

The electrical conductivity of (x)AgI–(1−x)ZnO (0⩽x⩽1) composites at room temperature increases with increasing AgI content and reaches a maximum at about 50% AgI. The results obtained by the scanning electron microscopy, X-ray diffractometry and photoluminescence spectroscopy have clarified high-ionic-conduction pathways related to mesoscopic defect structure at AgI/ZnO interfaces and mesoscopically disordered structure in AgI domain. We have observed also new optical phenomenon, which may arise from excitation energy transfer between AgI-exciton and photoinduced oxygen vacancy at the AgI/ZnO interface.

Structural, electrical and optical studies on AgI–anatase composites

AgI–anatase composites, (x)AgI–(1 − x)anatase,were fabricated over a wide composition range of 0–100% AgI for the first time.The electrical conductivity at 300 K increases with increasing AgI content andreaches a maximum (about 3 × 10−2 S m−1)at about 40% AgI. The conductivity is enhanced by about three orders ofmagnitude in comparison with that of pristine AgI. These composite specimenshave been characterized by both scanning electron microscopy and x-raydiffractometry. The observations with a scanning electron microscope show thatanatase fine particles are densely packed in an AgI particle of several micrometresin size and such composite particles are three-dimensionally connected to eachother to form a composite specimen. The photoluminescence (PL), PL excitationand time-resolved PL spectra of these composites have also been measured atdifferent temperatures between 8 and 278 K. The exciton spectra obtained relatedto the anatase particles and the AgI domains in anatase-packed AgI particles arediscussed in the light of the morphological, structural and conductivity data.