Production of opaque frits with low ZrO<Subscript>2</Subscript> and ZnO contents and their industrial uses for fast single-fired wall tile glazes

The amounts of zirconium and zinc oxides, which raise the production costs of ceramic glazes, were decreased in fast single-fired wall tile frit compositions and an industrial frit production was conducted. Opacity of the fired frit-based glazes was accomplished by compositional modifications of frits with no other nucleating agent. It was determined that the ratios of Al₂O₃/ΣR₂O, Al₂O₃/ΣRO, and Al₂O₃/B₂O₃ have significant effects on decreasing ZrO₂ and ZnO levels in the frit composition. A reduction of 25% in both zirconia and zinc oxide contents of frit batches, with respect to the reference frit (R) containing 6–10% ZrO₂ and 6–10% ZnO for a glossy white opaque wall tile glaze, was achieved in the ZD glaze consisting of 4.5–7.5% zirconia and 4.5–7.5% ZnO in its frit composition. It was concluded that zircon was the main crystalline phase of the glaze contributing the opacity. The ZD frit-based glaze has a thermal expansion coefficient value of 61.13 ± 0.32 × 10⁻⁷ °C⁻¹ at 400 °C which well matches to that of the wall tile body. TS EN ISO 10545 standard tests were also applied to the final ZD glaze. It is confirmed that the production cost of a fast single-fired wall tile glaze can be decreased by 15–20% with the successful new frit developed.     

Preparation and characterization of solid-state sintered aluminum-doped zinc oxide with different alumina contents

Aluminum-doped zinc oxide (AZO) ceramics with 0− 2 ·5 wt.% alumina (Al₂O₃) content were prepared using a solid-state reaction technique. It was found that AZO grains became finer in size and more irregular in shape than undoped ZnO as the Al₂O₃ content increased. Addition of Al₂O₃ dopant caused the formation of phase transformation stacking faults in ZnO grains. The second phase, ZnAl₂O₄ spinel, was observed at the grain boundaries and triple junctions, and inside the grains. In this study, a 3-inch circular Al₂O₃ (2 wt.%)-doped ZnO ceramic target sintered at 1500°C for 6 h has a relative density of 99·8% with a resistivity of 1·8 × 10^− 3 Ω-cm. The AZO film exhibits optical transparency of 90·3% in the visible region and shows an electrical resistivity of 2·5 × 10^− 3 Ω-cm.     

Crystallization characteristic and properties of some zinc containing soda lime silicate glasses

The crystallization behaviour of some soda lime silicate glasses modified by ZnO/CaO replacement to give the composition (Na₂O)₂·CaO_1−x ·(ZnO) _x ·3SiO₂ (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been investigated using differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD). The thermal expansion coefficients and AC electrical properties in the frequency range 40 Hz–5 MHz of the obtained crystalline products were determined. Two forms of sodium calcium silicate (Na₄CaSi₃O₉ & Na₂Ca₂Si₃O₉), sodium metasilicate-Na₂SiO₃, two types of sodium zinc silicate (Na_1.31Zn_0.655Si_1.345O₄ & Na₂ZnSiO₄) and α-quartz phases were mostly developed in the crystallized glasses using various heat-treatment processes. The coefficient of thermal expansion of the obtained glass–ceramic materials are between 120 × 10⁻⁷°K⁻¹ and 168 × 10⁻⁷°K⁻¹ in the 25°–600 °C temperature range. The increase of frequency generally resulted in the increase of the conductivity and decrease the dielectric constant together with the loss tangent of the glass–ceramic materials.     

Photoresponse of n -ZnO/ p -Si heterojunction towards ultraviolet/visible lights: thickness dependent behavior

A series of n-ZnO/p-Si thin film heterojunctions have been fabricated by a low cost sol–gel technique for different ZnO film thicknesses and the dark as well as photo current–voltage (I–V) characteristics have been investigated in details. The heterojunction with ZnO thickness of 0.46 μm shows the best diode characteristics in terms of rectification ratio, I _F/I _R = 5.7 × 10³ at 5 V and reverse leakage current density, J _R = 7.6 × 10⁻⁵ A cm⁻² at −5 V. From the photo I–V curves and wavelength dependent photocurrent of the heterojunctions, it is found that the junction with 0.46 μm ZnO thickness shows the highest sensitivity towards both UV and visible lights.     

ZnO nanocrystalline thin films: a correlation of microstructural,optoelectronic properties

The compositional, structural, microstructural, dc electrical conductivity and optical properties of undoped zinc oxide films prepared by the sol–gel process using a spin-coating technique were investigated. The ZnO films were obtained by 5 cycle spin-coated and dried zinc oxide films followed by annealing in air at 600 °C. The films deposited on the platinum coated silicon substrate were crystallized in a hexagonal wurtzite form. The energy-dispersive X-ray (EDX) spectrometry shows Zn and O elements in the products with an approximate molar ratio. TEM image of ZnO thin film shows that a grain of about 60–80 nm in size is really an aggregate of many small crystallites of around 10–20 nm. Electron diffraction pattern shows that the ZnO films exhibited hexagonal structure. The SEM micrograph showed that the films consist in nanocrystalline grains randomly distributed with voids in different regions. The dc conductivity found in the range of 10⁻⁵–10⁻⁶ (Ω cm)⁻¹. The optical study showed that the spectra for all samples give the transparency in the visible range.     

Surface and grain-boundary energies as well as surface mass transport in polycrystalline yttrium oxide

The sessile drop technique has been used to measure the temperature dependence of the contact angle, θ, of the liquid metals Ag and Cu in contact with polycrystalline yttrium oxide (yttria, Y₂O₃) at the temperature range 1,333–1,773 K in Ar/4%H₂ atmosphere. Combination of the experimental results with literature data taken for nonwetted and nonreactive oxide/liquid metal systems permit the calculation of the surface energy of Y₂O₃ as γ_sv (J/m²) = 2.278–0.391 × 10⁻³ T. For the same atmospheric conditions, thermal etching experiments on the grain boundaries intersecting the surface of the polycrystalline ceramic allow to determine the groove angles, ψ, with respect to temperature and time as well as the grain-boundary energy of Y₂O₃ as γ_ss (J/m²) = 1.785–0.306 × 10⁻³ T. Grain-boundary grooving studies on polished surfaces of Y₂O₃ annealed in Ar/4%H₂ atmosphere between 1,553 K and 1,873 K have shown that surface diffusion is the dominant mechanism for the mass transport. The surface diffusion coefficient can be expressed according to the equation D _s (m²/s) = 1.22 × 10⁻³ exp(−343554/RT).     

Insulating ZnO film on silicon for MIS application

High resistive zinc oxide thin film (∼ 0·5 μm) was deposited on single crystalp-silicon (100) wafers by an inexpensive spray-CVD method and was characterized both optically and electrically. Al/ZnO/Si (MIS) device structure was subsequently fabricated and bothI − V andC − V characteristics were studied. The semiconductor-insulator interface charge density (D _it) was calculated by Terman method and was found to be 3·85 × 10¹¹ cm⁻²eV⁻¹.     

Interfacial interaction of solid cobalt with liquid Pb-free Sn–Bi–In–Zn–Sb soldering alloys

Dissolution kinetics of cobalt in liquid 87.5%Sn–7.5%Bi–3%In–1%Zn–1%Sb and 80%Sn–15%Bi–3%In–1%Zn–1%Sb soldering alloys and phase formation at the cobalt–solder interface have been investigated in the temperature range of 250–450 °C. The temperature dependence of the cobalt solubility in soldering alloys was found to obey a relation of the Arrhenius type c _s = 4.06 × 10² exp (−46300/RT) mass% for the former alloy and c _s = 5.46 × 10² exp (−49200/RT) mass% for the latter, where R is in J mol⁻¹ K⁻¹ and T in K. For tin, the appropriate equation is c _s = 4.08 × 10² exp (−45200/RT) mass%. The dissolution rate constants are rather close for these soldering alloys and vary in the range (1–9) × 10⁻⁵ m s⁻¹ at disc rotational speeds of 6.45–82.4 rad s⁻¹. For both alloys, the CoSn₃ intermetallic layer is formed at the interface of cobalt and the saturated or undersaturated solder melt at 250 °C and dipping times up to 1800 s, whereas the CoSn₂ intermetallic layer occurs at higher temperatures of 300–450 °C. Formation of an additional intermetallic layer (around 1.5 μm thick) of the CoSn compound was only observed at 450 °C and a dipping time of 1800 s. A simple mathematical equation is proposed to evaluate the intermetallic-layer thickness in the case of undersaturated melts. The tensile strength of the cobalt-to-solder joints is 95–107 MPa, with the relative elongation being 2.0–2.6%.     

Studies on tin oxide films prepared by electron beam evaporation and spray pyrolysis methods

Transparent conducting tin oxide thin films have been prepared by electron beam evaporation and spray pyrolysis methods. Structural, optical and electrical properties were studied under different preparation conditions like substrate temperature, solution flow rate and rate of deposition. Resistivity of undoped evaporated films varied from 2.65 × 10⁻² ω-cm to 3.57 × 10⁻³ ω-cm in the temperature range 150–200°C. For undoped spray pyrolyzed films, the resistivity was observed to be in the range 1.2 × 10⁻¹ to 1.69 × 10⁻² ω-cm in the temperature range 250–370° C. Hall effect measurements indicated that the mobility as well as carrier concentration of evaporated films were greater than that of spray deposited films. The lowest resistivity for antimony doped tin oxide film was found to be 7.74 × 10⁻⁴ ω-cm, which was deposited at 350°C with 0.26 g of SbCl₃ and 4 g of SnCl₄ (SbCl₃/SnCl₄ = 0.065). Evaporated films were found to be amorphous in the temperature range up to 200°C, whereas spray pyrolyzed films prepared at substrate temperature of 300– 370°C were poly crystalline. The morphology of tin oxide films was studied using SEM.     

Preparation, proton conduction, and application in ammonia synthesis at atmospheric pressure of La0.9Ba0.1Ga1– x Mg x O3–α

La_0.9Ba_0.1Ga_1–x Mg _x O_3–α (0 ≤ x ≤ 0.25) was prepared by the microemulsion method. A single phase of LaGaO₃ perovskite structure was formed when x was ≥0.15. Electrochemical hydrogen permeation (hydrogen pumping) proved that La_0.9Ba_0.1Ga_1–x Mg _x O_3–α had proton conduction, and the proton conduction was measured by AC impedance spectroscopy method from 400 to 800 °C in hydrogen atmospheres. Among these samples, La_0.9Ba_0.1Ga_0.8Mg_0.2O_3–α has the highest proton conductivity with the values of 9.51 × 10⁻⁴ to 4.68 × 10⁻² S cm⁻¹ at 400–800 °C. Ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in an electrolytic cell using La_0.9Ba_0.1Ga_0.8Mg_0.2O_3–α as electrolyte. The rate of NH₃ formation was 1.89 × 10⁻⁹ mol s⁻¹ cm⁻² at 520 °C upon imposing a current of 1 mA through the cell.     

Synthesis of nanocrystalline materials through reverse micelles: A versatile methodology for synthesis of complex metal oxides

We have been successful in obtaining monophasic nanosized oxides with varying chemical compositions using the reverse micellar method. Here we describe our methodology to obtain important metal oxides like ceria, zirconia and zinc oxide. The oxalate of cerium, zirconium and zinc were synthesized using the reverse micellar route. While nanorods of zinc oxalate with dimension, 120 nm in diameter and 600 nm in length, could be obtained, whereas spherical particles of size, 4–6 nm, were obtained for cerium oxalate. These precursors were heated to form their respective oxides. Mixture of nanorods and nanoparticles of cerium oxide was obtained. ZrO₂ nanoparticles of 3–4 nm size were obtained by the thermal decomposition of zirconium oxalate precursor. ZnO nanoparticles (55 nm) were obtained by the decomposition of zinc oxalate nanorods. Photoluminescence (PL) studies at 20 K shows the presence of three peaks corresponding to free excitonic emission, free to bound and donor-acceptor transitions. We also synthesized nanoparticles corresponding to Ba_1−x Pb _x ZrO₃ using the reverse micellar route. The dielectric constant and loss were stable with frequency and temperature for the solid solution.     

Thermal and Doping Effect on Sn/(n)ZnO Schottky Junction and Its Performance as a <Emphasis Type="Italic">PV</Emphasis> Effect

Thin film Sn/(n)ZnO Schottky junctions with different doping concentrations were prepared by vacuum evaporation. Different junction parameters such as ideality factor, barrier height, Richardson’s constant, short-circuit current, etc. were determined from I–V characteristics. These parameters were found to change significantly with variations of doping concentration and temperature. The structures showed the change of the PV effect, giving a fill factor of 0.42 (efficiency of 0.39 %) with an open-circuit voltage of 124mV and a short-circuit current density of 113 × 10⁻⁵ A ·cm⁻² for a doping concentration, N _d = 3.88 × 10¹⁵ cm ⁻³(2.74 % Al-doped ZnO). However, by increasing the doping concentration, the efficiency was found to increase by up to 4.54 % for doping concentration, N _d = 2.28 × 10¹⁷ cm ⁻³. The conversion efficiencies varied with temperature and were observed to have an overall improvement up to 343 K. Proper doping, annealing, and hydrogenation are necessary to reduce the series resistance so as to achieve an ideal and high efficiency PVconverter.     

Thermal and dielectric properties of the LTCC composites based on the eutectic system BaO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>

The low-temperature co-fired ceramic (LTCC) composites containing quartz based on the eutectic system BaO–Al₂O₃–SiO₂–B₂O₃ are fabricated at the sintering temperature below 980 °C. Preparation process and sintering mechanism were described and discussed, respectively. The results indicated that the addition of quartz to the eutectic system can availably improve dielectric properties of the LTCC composites. In addition, The LTCC composites with optimum compositions, which were obtained by the regulation of an Al₂O₃ content in the composite, can express excellent dielectric properties (permittivity: 5.94, 5.48; loss: 7 × 10⁻⁴, 5 × 10⁻⁴), considerable CTE values (11.7 ppm. °C⁻¹, 10.6 ppm. °C⁻¹) and good mechanical properties (128 MPa,133 MPa).     

Synthesis and characterization of metal oxide nanorod brushes

Nanorod brushes of α-Al₂O₃, MoO₃ and ZnO have been synthesized using amorphous carbon nanotube (a-CNT) brushes as the starting material. The brushes of α-Al₂O₃ and MoO₃ are made up of single crystalline nanorods. In the case of ZnO brushes, the nanorod bristles are made by the fusion of 15–25 nm size nanoparticles and are porous in nature. Metal oxide nanorod brushes thus obtained have been characterized by XRD, FESEM, TEM and Raman spectroscopy. Single crystalline ruby nanorods were obtained by introducing chromium ions during the synthesis of alumina rods.     

Characterization of NaPO3–SnO–WO3 glasses prepared by microwave heating

Phosphate glasses containing tin and tungsten oxides were produced by microwave heating under a nitrogen protective atmosphere. Microwaves permit to heat the raw materials at temperatures close to 1000 °C in short time and to obtain homogeneous glasses in less than 10 min. All samples were characterized from thermal and mechanical point of view as function of metal oxide proportions. The equimolar addition of SnO and WO₃ in sodium phosphate matrix involves a linear evolution of the different properties (T _g, CTE, density, mechanical properties, and durability). Thus, we have shown a progressive strengthening of the network. The glass transition temperature does not exceed 405 °C, and the chemical durability is improved to four orders of magnitude. The dissolution rate is equal to 3.4 × 10⁻⁷ g cm⁻² min⁻¹ for 40NaPO₃–30SnO–30WO₃ glass composition and is comparable with those of the window glass.     

Electrical characterization of low temperature deposited oxide films on ZnO/<Emphasis Type="Italic">n</Emphasis>-Si substrate

Thin films of silicon dioxide are deposited on ZnO/n-Si substrate at a low temperature using tetra-ethylorthosilicate (TEOS). The ZnO/n-Si films have been characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The border trap density (Q_bt) and fixed oxide charge density (Q_f/q) of the SiO₂/ZnO/n-Si films are found to be 3.9 × 10¹⁰ cm⁻² and 1.048 × 10¹¹ cm⁻², respectively. The trapping characteristics and stress induced leakage current (SILC) have also been studied under Fowler-Nordheim (F-N) constant current stressing.     

The kinetics of water loss from zinc phosphate and zinc polycarboxylate dental cements

The water desorption behaviour of three different zinc oxide dental cements (two polycarboxylates, one phosphate) has been studied in detail. Disc-shaped specimens of each material were prepared and allowed to lose water by being subjected to a low humidity desiccating atmosphere over concentrated sulfuric acid. In all three cements, water loss was found to follow Fick’s second law for at least 6 h (until M_t/M_∞ values were around 0.5), with diffusion coefficients ranging from 6.03 × 10⁻⁸ cm² s⁻¹ (for the zinc phosphate) to 2.056 × 10⁻⁷ cm² s⁻¹ (for one of the zinc polycarboxylates, Poly F Plus). Equilibration times for desorption were of the order of 8 weeks, and equilibrium water losses ranged from 7.1% for zinc phosphate to 16.9% and 17.4% for the two zinc polycarboxylates.     

Creep behavior of AZ31 magnesium alloy in low temperature range between 423 K and 473 K

The deformation behavior of coarse-grained AZ31 magnesium alloy was examined in creep at low temperatures below 0.5 T _m and low strain rates below 5 × 10⁻⁴ s⁻¹. The creep test was conducted in the temperature range between 423 and 473 K (0.46–0.51 T _m) under various constant stresses covering the strain rate range 5 × 10⁻⁸ s⁻¹–5 × 10⁻⁴ s⁻¹. All of the creep curves exhibited two types depending on stress level. At low stress (σ/G < 4 × 10³), the creep curve was typical of class I behavior. However, at high stresses (σ/G > 4 × 10³), the creep curve was typical of class II. At the low stress level, deformation could be well described by solute drag creep whereas at the high stress level, deformation could be well described by dislocation climb creep associated with pipe diffusion or lattice diffusion. The transition of deformation mechanism from solute drag creep to dislocation climb creep, on the other hand, could be explained in terms of solute-atmosphere-breakaway concept.     

Titanium-doped indium oxide films prepared by d.c. magnetron sputtering using ceramic target

Polycrystalline thin films of Ti-doped indium oxide (indium–titanium-oxide, ITiO) were prepared by d.c. magnetron sputtering and their electrical and optical properties were investigated. Doping of Ti was effective in improvement of the electroconductivity of the indium oxide: the electrical resistivity of 1.7 × 10⁻³ Ω cm of non-doping decreased to minimum value of 1.8 × 10⁻⁴ Ω cm at 2.4 at.% Ti-doping when the films were deposited at 300 °C. The polycrystalline ITiO films of 0.8–1.6 at. % Ti-doping showed the high Hall mobilitiy (82–90 cm² V⁻¹ s⁻¹) and the relatively low carrier density (2.4–3.5 × 10²⁰ cm⁻³) resulting in characteristics of both low resistivity (2.1–3.0 × 10⁻⁴ Ω cm) and high transmittance in the near-infrared region (over 80% at 1550 nm), which cannot be shown in the conventional Sn-doped indium oxide (ITO) films.     

Preparation and properties of low-temperature co-fired ceramic of CaO–SiO2–B2O3 system

Low temperature co-fired ceramic (LTCC) was prepared by sintering a glass selected from CaO–SiO₂–B₂O₃ system, in which 0.5 wt% P₂O₅ and 0.5 wt% ZnO were added to optimize the preparation conditions. The glass powder and sintered bodies were characterized by different analytical techniques such as TG-DTA analysis, X-ray diffraction and Scanning electron microscopy. It was found that the optimal sintering temperature was 820°C based on the microstructure and the properties of sintering bodies, and then the major phases of the LTCC were CaSiO₃, CaB₂O₄ and SiO₂. The obtained products, with dielectric constant about 6.5, dielectric loss about 2 × 10⁻³ at 30 MHz and coefficient of thermal expansion about 8 × 10⁻⁶ °C⁻¹ between 20 and 400°C, are supposed to be suitable for application in wireless communications.