Elastic properties of Li<Subscript>2</Subscript>Zn<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> single crystals

The complete elastic modulus matrix of Li₂Zn₂(MoO₄)₃ single crystals has been measured for the first time. The sound velocity has been measured in different directions of the crystals by a pulse-phase method. The measurement results have been used to calculate elastic moduli. The sound velocity has been calculated in the three main crystallographic planes of the crystals.     

Elastic properties and spectroscopic studies of Na2O-ZnO-B2O3 glass system

Elastic properties,¹¹B MAS-NMR and IR spectroscopic studies have been employed to study the structure of Na₂O-ZnO-B₂O₃ glasses. Sound velocities and elastic moduli such as longitudinal, Young’s, bulk and shear modulus have been measured at a frequency of 10 MHz as a function of ZnO concentration. Both sound velocities and elastic moduli increase with increasing ZnO concentration. Poisson’s ratio and Debye temperature were also found to increase with ZnO concentration.¹¹B MAS-NMR and IR spectra show characteristic features of borate network and compositional dependence trends as a function of Na₂O/ZnO concentration. The results are discussed in view of borate network and dual structural role of Zn²⁺ ion into the network. The results indicate that the Zn²⁺ ions are likely to occupy network forming positions in this glass system.     

Synthesis and structural studies of Na<Subscript>2</Subscript>O-ZnO-ZnF<Subscript>2</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> oxyfluoride glasses

This paper describes the synthesis and spectroscopic studies of the glass system, 20Na₂O-(20-x) ZnO-xZnF₂-60B₂O₃(x = 0, 5, 10, 15, 20), prepared by melt quenching method. The analyses of DSC and XRD did not show the crystallinity of the glass sample. ¹¹B MAS-NMR shows the presence of sharp peak around −14 ppm. From the IR studies, the broadening of the peak around 1200–1400 and 800–1100 cm⁻¹ shows the presence of mixed linkages like B-O-B, B-O-Zn in the network.     

Structural changes induced by Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> addition in strontium-borate glass matrix

Glasses of the xFe₂O₃·(100−x)[B₂O₃·SrO] system, with 0 ≤ x ≤ 30 mol% were studied by X-ray diffraction, density, optical microscopy and FT-IR spectroscopy measurements. The X-ray patterns for the prepared system show that vitreous phase is present only in the sample with x < 40 mol%. For x ≥ 40 mol% in the studied samples is evidenced crystalline phase of Fe₂O₃. SEM measurements for the sample with x = 40 mol% shows that there are formed Fe₂O₃ microcrystallites with 10–20 μm dimension. FT-IR spectroscopy measurements shown that BO₃ and BO₄ are the main structural units of the glass system and the iron ions are located in the glass network.     

Effect of structure change on thermal and dielectric characteristics in low-temperature firing Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO glasses

In a Bi₂O₃–B₂O₃–ZnO glass system, glass structure change, sintering behavior and resultant physical characteristics of the glass were examined when various amounts of Bi₂O₃ and ZnO mixture were added. When the total amount of Bi₂O₃ and ZnO was below 30 mol%, a phase separation occurred and homogeneous glass was not obtained. The fraction of four-coordinated borons (BO₄) was highest when the total amount of Bi₂O₃ and ZnO was 50mol%. Further addition over 50 mol% induced a borate anomaly phenomenon in the glass, which resulted in the decrease in BO₄ fraction. The sintering temperature and glass transition temperature decreased as the amount of Bi₂O₃ and ZnO increased. The thermal expansion coefficient and dielectric constant of the specimens were also examined.     

Effects of SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> fillers on thermal and dielectric properties of eco-friendly bismuth glass microcomposites of plasma display panels

The effects of SiO₂ (amorphous) and TiO₂ (crystalline, rutile) fillers on softening point (T _s), glass transition temperature (T _g), coefficient of thermal expansion (CTE), and dielectric constant (ɛ) of zinc bismuth borate, ZnO-Bi₂O₃-B₂O₃ (ZBIB) glass microcomposites have been investigated with a view to its use as the white back (rear glass dielectric layer) of plasma display panels (PDPs). The experimentally measured properties have also been compared with those of theoretically predicted values. Both the experimental and theoretical trends of these properties with added filler contents correlate very well. The interaction of fillers with glass which occurred during sintering at 560°C has also been monitored by XRD and FTIR spectroscopic analyses. The microstructures and distribution of fillers in the glass matrix have been analyzed by SEM images. It is observed that the fillers have partially dissolved in the glass at the firing temperature leaving some unreacted filler as residue which results in ceramic-glass microcomposites. In consideration of the desired properties of white back of PDPs, the addition of TiO₂ filler to ZBIB glass is found to be more preferable than SiO₂ filler. The addition of 10 wt% TiO₂ filler yielded T _s, T _g, CTE and ɛ values of 560°C, 480°C, 82 × 10⁻⁷/K and 14·6 which are found to meet the desired values of <580°C, <500°C, <83 × 10⁻⁷/K and <15, respectively with respect to use of PD200 glass as substrate in PDP technology.     

Elastic properties of phosphotungstate glasses

Elastic properties of potassium and lead phosphotungstate glasses have been investigated using ultrasonic velocity measurements. The composition dependence of elastic moduli in WO₃-K₂O-P₂O₅ glasses suggests that at low alkali oxide concentrations the atomic ring size increases by network modification, which results in the decrease of elastic moduli. In the highly modified regime, due to the presence of coulombic interaction, the rate of decrease of elastic moduli is reduced. In the WO₃-PbO-P₂O₅ glasses the behaviour of elastic moduli suggests that PbO behaves both as a network former and network modifier. The incorporation of PbO into the network is quantitatively determined by the concentration of P₂O₅ in the system. The results are consistent with the structural model proposed earlier, based on characterization studies.     

Electrical and physicochemical properties of some Ag<Subscript>2</Subscript>O-containing lithia iron silica phosphate glasses

The present paper reports the influence of Ag₂O addition at the expense of Li₂O on the local structure of xAg₂O·(30 − x)Li₂O·10Fe₂O₃·10SiO₂·50P₂O₅ glass matrix (with x = 0, 0.5, 1, 1.5 and 2 mol %). The phosphate structural units of the network former are assessed from Fourier transform infrared (FT-IR) spectroscopy. The addition of Ag₂O to the glass network matrix ≤1 mol % leads to the occurrence of a depolymerization process of the phosphate structure and consequently, to the appearance of a distortion of the PO₄ tetrahedra. When the content of Ag₂O is increased from 1.5 up to 2 mol %, a remarkable polymerization process has been observed. The density, molar volume, microhardness and chemical durability have been investigated in order to study the effect of Ag₂O/Li₂O replacements on the physicochemical properties the studied glasses. The AC electrical properties are affected to a great extent with composition. These results are related to the internal structure of the glass samples. The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response in the interval 100 Hz–100 kHz and the effect of compositional changes on the measured properties was investigated. Measurements showed that the electrical responses of glass samples were different and complex for interpretation. The increase of Ag₂O addition at the expense of Li₂O contents (from 0 to 1 mol %) led to increase the conductivity, dielectric constant and dielectric losses of samples. The addition of more Ag₂O at the expense of Li₂O (from 1.5 to 2 mol %), resulting into decreasing the conductivity, the dielectric constant and dielectric losses of the studied glasses. The experimental data of the glass samples were argued to the internal structure of the glasses and the nature and role-played by weakening or increasing the rigidity of the structure of the sample. It could be concluded, therefore, that the AC electrical properties of the samples were influenced by the distribution of its constituents, connectivity, and number of free charges.     

Formation,thermal, optical and physical properties of GeS<Subscript>2</Subscript>–Ga<Subscript>2</Subscript>S<Subscript>3</Subscript>–AgCl novel chalcohalide glasses

Novel GeS₂–Ga₂S₃–AgCl chalcohalide glasses had been prepared by melt-quenching technique, and the glass-forming region was determined by XRD, which indicated that the maximum of dissolvable AgCl was up to 65 mol%. Thermal and optical properties of the glasses were studied by differential scanning calorimetry (DSC) and Visible-IR transmission, which showed that most of GeS₂–Ga₂S₃–AgCl glasses had strong glass-forming ability and broad region of transmission (about 0.45–12.5 μm). With the addition of AgCl, the glass transition temperature, Tg decreases distinctly, and the short-wavelength cut-off edge (λ_vis) of the glasses also shifts to the long wavelength gradually. However, the glass-forming ability of the glass has a complicated evolutional trend depended on the compositional change. In addition, the values of the Vickers microhardness, H _v , which decrease with the addition of AgCl, are high enough for the practical applications. These excellent properties of GeS₂–Ga₂S₃–AgCl glasses make them potentially applied in the optoelectronic field, such as all-optical switch, etc.     

Study of structure and properties of ZnO–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Glasses of the ternary system ZnO–Bi₂O₃–P₂O₅ were prepared and studied in two compositional series 50ZnO–xBi₂O₃–(50 − x)P₂O₅ and (50 − y)ZnO–yBi₂O₃–50P₂O₅. Two distinct glass-forming regions were found in the 50ZnO–xBi₂O₃–(50 − x)P₂O₅ glass series with x = 0–10 and 20–35 mol.% Bi₂O₃. All prepared Bi₂O₃-containing glasses reveal a high chemical durability. Small additions of Bi₂O₃ (∼5 mol.%) improve thermal stability of glasses. All glasses crystallize on heating within the temperature range of 505–583 °C. Structural studies by Raman and ³¹P MAS NMR spectroscopies showed the rapid depolymerisation of phosphate chains within the first region with x = 0–15 and the presence of isolated Q⁰ phosphate units within the second region with x = 20–35. Raman studies showed that bismuth is incorporated in the glass structure in BiO₆ units and their vibrational bands were observed within the spectral region of 350–700 cm⁻¹. The evolution of properties and the spectroscopic data are both in accordance with a network former effect of Bi₂O₃.     

Elastic properties and spectroscopic studies of fast ion conducting Li2OZnOB2O3 glass system

Glass systems of the composition xLi₂O-20ZnO-(80 − x)B₂O₃ where (x = 5, 10, 15, 20, 25 and 30 mol%) have been prepared by melt quenching technique. Elastic properties, ¹¹B MAS-NMR and IR spectroscopic studies have been employed to study the structure of Li₂O-ZnO-B₂O₃ glasses. Elastic properties have been investigated using sound velocity measurements at 10 MHz. Elastic moduli reveal trends in their compositional dependence. The bulk modulus and shear modulus increases monotonically with increase of BO₄ units, which increase the dimensionality of the network. ¹¹B MAS-NMR and IR spectra show characteristic features of borate network and compositional dependent trends as a function of Li₂O/ZnO concentration. The results are discussed in view of borate network and the dual structural role of Zn²⁺ ions. The results indicate that the Zn²⁺ are likely to occupy network-forming positions in this glass system.     

Low-loss,high-purity (TeO<Subscript>2</Subscript>)<Subscript>0.75</Subscript>(WO<Subscript>3</Subscript>)<Subscript>0.25</Subscript> glass

By melting a mixture of high-purity oxides in a platinum crucible under flowing purified oxygen, we have prepared (TeO₂)_0.75(WO₃)_0.25 glass with a total content of 3d transition metals (Fe, Ni, Co, Cu, Mn, Cr, and V) within 0.4 ppm by weight, a concentration of scattering centers larger than 300 nm in size below 10² cm⁻³, and an absorption coefficient for OH groups (λ ∼ 3 μm) of 0.008 cm⁻¹. The absorption loss in the glass has been determined to be 115 dB/km at λ = 1.06 μm, 86 dB/km at λ = 1.56 μm, and 100 dB/km at λ = 1.97 μm. From reported specific absorptions of impurities in fluorozirconate glasses and the impurity composition of the glass studied here, the absorption loss at λ ∼ 2 μm has been estimated at ≤100 dB/km. The glass has been drawn into a glass-polymer fiber, and the optical loss spectrum of the fiber has been measured.     

Crystal growth and elastic properties of In<Subscript>2</Subscript>Se<Subscript>3</Subscript>

Perfect α-In₂Se₃ single crystals have been grown, and ultrasound velocities, v _i (i = 1–7), have been measured in single-crystal α-In₂Se₃ in various directions for different polarizations. We have determined the components of its elastic tensor (C _ij ) and calculated its elastic characteristics: elastic compliance, Young’s modulus, shear modulus, linear and volume compressibilities, bulk modulus, and Poisson’s ratio.     

Elastic constants of the iron oxide doped yttria-stabilized zirconia

Ultrasonic compressional and shear wave velocity measurements have been made on the (ZrO₂)_1−A (Y₂O₃)_A−X (Fe₂O₃) _X system at 5 MHz. The amounts of Fe₂O₃ dopant ranging from 0 up to 10 mol% were mixed with the ceramic matrix. In this paper the ultrasonic compressional and shear wave velocity measurements made on this system at room temperature are discussed. The elastic moduli, Poisson's ratio and density are found to be sensitive to the additions of the Fe₂O₃ dopant and they show an anomalous behaviour. A qualitative explanation of the compositional dependence of the elastic moduli and Poisson's ratio is given in terms of changes in packing density, bond strength, co-ordination number and cross-link density.     

Effect of secondary heat treatment on the spectroscopic properties of Na<Subscript>2</Subscript>O-Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

We have studied the optical absorption and luminescence spectra of 45Na₂O · xNb₂O₅ · (55 − x)P₂O₅ glasses containing 5, 10, 20, 25, 30, and 35 mol % Nb₂O₅. The results indicate that the absorption band around 26000 cm⁻¹, responsible for the yellow color of the glasses, is due to the [Nb^(5+)--O⁻] center and disappears upon secondary heat treatment. Heat treatment of europium-doped glasses increases the concentration of Eu³⁺ centers in an asymmetric environment, which is accompanied by an increase in luminescence efficiency. The reason for this is that the Eu³⁺ ions are located outside the niobate subsystem of the glass matrix. The europium in the glasses studied acts as a protector ion.     

Optical properties of CeO<Subscript>2</Subscript> thin films

Cerium oxide (CeO₂) thin films have been prepared by electron beam evaporation technique onto glass substrate at a pressure of about 6 × 10⁻⁶ Torr. The thickness of CeO₂ films ranges from 140–180 nm. The optical properties of cerium oxide films are studied in the wavelength range of 200–850 nm. The film is highly transparent in the visible region. It is also observed that the film has low reflectance in the ultra-violet region. The optical band gap of the film is determined and is found to decrease with the increase of film thickness. The values of absorption coefficient, extinction coefficient, refractive index, dielectric constant, phase angle and loss angle have been calculated from the optical measurements. The X-ray diffraction of the film showed that the film is crystalline in nature. The crystallite size of CeO₂ films have been evaluated and found to be small. The experimental d-values of the film agreed closely with the standard values.     

Enhancement in electrical conductivity of Li<Subscript>2</Subscript>O: B<Subscript>2</Subscript>O<Subscript>3</Subscript>: V<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

The study of electrical conductivity of 30Li₂O: (70 − x) B₂O₃: xV₂O₅ glass samples has been carried out. The results have been explained by dividing the temperature range into two regions. In region I, conductivity shows Arrhenius behaviour for all the samples. The conductivity increases with addition of V₂O₅. The results have been explained in the light of Anderson and Stuart Model. In region II, an anomalous enhancement in the conductivity is observed for all the samples up to certain temperature beyond which the conductivity decreases. The enhancement in the conductivity in the annealed glass sample has been attributed to nanocrystallization.     

Formation of Li<Superscript>+</Superscript> superionic crystals from the Li<Subscript>2</Subscript>S–P<Subscript>2</Subscript>S<Subscript>5</Subscript> melt-quenched glasses

The 70Li₂S·30P₂S₅ (mol%) glass was prepared by the melt quenching method and the glass–ceramic electrolytes were obtained by heating the prepared glass over crystallization temperatures. The superionic metastable Li₇P₃S₁₁ crystal was formed by heating the glass in the temperature range from 280 and 360 °C. The conductivity of the glass–ceramics was enhanced by the precipitation and growth of the Li₇P₃S₁₁ crystal, and the highest conductivity of 4.1 × 10⁻³ S cm⁻¹ at room temperature was achieved in the glass–ceramic heated at 360 °C for 1 h. The Li₇P₃S₁₁ crystal changed into the thermodynamically stable phase such as the Li₄P₂S₆ crystal with further increasing heat treatment temperature and holding time, resulting in lowering conductivities of the glass–ceramics.     

Spectroscopic studies of TeO<Subscript>2</Subscript>–ZnO–Er<Subscript>2</Subscript>O<Subscript>3</Subscript> glass system

Series of glass based on the (80 − x)TeO₂–20ZnO–(x)Er₂O₃ system (0.5 mol% ≤ x ≤ 2.5 mol%) has successfully been made by melt quenching technique. The optical properties of glass have been investigated by means of IR and Raman spectroscopy. It is observed that as the Er₂O₃ content is being increased, the sharp IR absorption peaks are consistently shifted from 650 to 672 cm⁻¹ while the Raman shift intensity around 640–670 cm⁻¹ is decreases but increases around 720–740 cm⁻¹. It is found out that both phenomenons are related to the structural changes between the stretching vibration mode of TeO₄ tbp and TeO₃ tp, and bending vibration mode of Te–O bonds in the glass linkages.     

Ionic conductivity of BaF<Subscript>2</Subscript> + ZnF<Subscript>2</Subscript> + CdF<Subscript>2</Subscript> + YbF<Subscript>3</Subscript> optical fluoride ceramic

The electrical conductivity of an optical fluoride ceramic in the quaternary system BaF₂ + ZnF₂ + CdF₂ + YbF₃ has been determined in the temperature range 338–722 K using impedance spectroscopy (5 to 5 × 10⁵ Hz). The 500-K ionic conductivity of the ceramic is σ = 3.3 × 10^–4 S/cm, which corresponds to the electrical characteristics of single crystals of the best conducting nonstoichiometric M_1–x R _x F_{2 + x} (M = Sr, Ba; R = La–Nd; x = 0.3–0.5) fluorite phases. We have observed nonmonotonic variation (breaks) in temperature-dependent σ, which is due to competing fluoride ion transport processes in different parts of the ceramic sample. The highly conductive state of the BaF₂ + ZnF₂ + CdF₂ + YbF₃ fluoride ceramic seems to be due to the formation of structural regions corresponding to a Ba_1–x Yb _x F_{2 + x} solid solution.