Abstract: This study probes the effect of annealing temperature on electrical, optical and microstructural properties of indium tin oxide (ITO) films deposited onto soda lime glass substrates by conventional direct current (DC) magnetron reactive sputtering technique at 100 watt using an ITO ceramic target (In2O3:SnO2, 90:10 wt%) in argon atmosphere at room temperature. The films obtained are exposed to the calcination process at different temperature up to 700 °C. X–ray diffractometer (XRD), ultra violet-visible spectrometer (UV–vis) and atomic force microscopy (AFM) measurements are performed to characterize the samples. Moreover, phase purity, surface morphology, optical and photocatalytic properties of the films are compared with each other. The results obtained show that all the properties depend strongly on the annealing temperature. XRD results indicate that all the samples produced contain the In2O3 phase only and exhibit the polycrystalline and cubic bixbite structure with more intensity of diffraction lines with increasing the annealing temperature until 400 °C; in fact the strongest intensity of (222) peak is obtained for the sample annealed at 400 °C, meaning that the sample has the greatest ratio I222/I400 and the maximum grain size (54 nm). As for the AFM results, the sample prepared at 400 °C has the best microstructure with the lower surface roughness. Additionally, the transmittance measurements illustrate that the amplitude of interference oscillation is in the range from 78 (for the film annealed at 400 °C) to 93 % (for the film annealed at 100 °C). The refractive index, packing density, porosity and optical band gap of the ITO thin films are also evaluated from the transmittance spectra. According to the results, the film annealed at 400 °C obtains the better optical properties due to the high refractive index while the film produced at 100 °C exhibits much better photoactivity than the other films as a result of the large optical energy band gap.

Abstract: Thin films of semiconducting polyaniline (PANi) nanofibers reinforced with copper oxide (CuO) nanoparticles (NPs) were prepared on glass substrate using spin coating technique. Polyaniline (PANi) have been synthesized by chemical oxidative polymerization method with monomer aniline in presence of (NH4)2S2O8 as an oxidant at 0 °C. The copper oxide (CuO) nanoparticles were synthesized by sol–gel method. Physical properties of nanocomposite (NCs) films were characterized and analyzed by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, UV–vis spectroscopy, Two probe resistivity measurement technique and Thermo-emf measurement. Structural analysis showed that the crystal structure of CuO is not disturbed in the PANi–CuO hybrid nanocomposite. Surface morphology study shows the uniform distribution of CuO nanoparticles in PANi matrix. FTIR and UV–Visible studies confirm the presence of polyaniline in emeraldine base form in the composites and suggest incorporation of CuO in polymer. Two probe electrical resistivity measurements of nanocomposites (NCs) film revealed that the resistivity of PANi increases with increasing content of CuO NPs.

Abstract: With more consumer products moving towards environmentally friendly packaging, making solder Pb-free has become an urgent task for electronics assemblies. Solder joints are responsible for both electrical and mechanical connections. Solder joint does not have adequate ductility to ensure the repeated relative displacements due to the mismatch between expansion coefficients of the chip carrier and the circuit board. Materials behavior of solder joints involves a creep–fatigue interaction, making it a poor material for mechanical connections. The reliability of solder joints of electronics components has been found playing a more important role in service for microelectronics components and micro-electro-mechanical systems. So many researchers in the world investigated reliability of solder joints based on finite element simulation and experiments about the electronics devices, such as CR, QFP, QFN, PLCC, BGA, CSP, FCBGA and CCGA, which were reviewed systematically and extensively. Synchronously the investigation on reliability of solder joints was improved further with the high-speed development of lead-free electronic packaging, especially the constitutive equations and the fatigue life prediction equations. In this paper, the application and research status of constitutive equations and fatigue life prediction equations were reviewed, which provide theoretic guide for the reliability of lead-free solder joints.

Abstract: Due to its high mechanical hardness and excellent chemical inertness, SiC single-crystal wafer is extremely difficult to realize effectively removed total planarization. Owing to crystalline polarity and anisotropy, material removal rate (MRR) on Si-face (0001) of SiC wafer is significantly lower than C-face (000 $$ \bar{1} $$ ) for a defect-free surface. In the paper, the slurry containing hydrogen peroxide (H2O2), potassium hydroxide and abrasive colloidal silica, is introduced to chemical mechanical polishing (CMP) of on-axis Si-face 6H-SiC wafer, resulting in acquiring high MRR with 105 nm/h, and atomically flat defect-free surface with atomic step-terrace structure and roughness of 0.0667 nm by atomic force microscope (AFM), in order to satisfy further demands of electronic device fabrication towards substrate wafer performance. The effects of the three ingredients in the slurry towards MRR of SiC wafer, polished surface quality and coefficient of friction in polishing process are studied. Optical microscope, optical interferometry profiler and AFM are used to observe the polished surface. In addition, the CMP removal mechanism of SiC wafer and the formation of ultra-smooth surface are discussed.

Abstract: Cu-doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Cu:Zn atomic ratio from 0 to 5 % The synthesis process was based on the hydrolysis of zinc acetate dehydrate and copper acetate tetrahydrate heated under reflux to 65 °C using methanol as a solvent X-ray diffraction (XRD) analysis reveals that the Cu-doped ZnO crystallize in a wurtzite structure with a change of crystal size from 12 nm for undoped ZnO to 5 nm for Cu-doped ZnO These nano size crystallites of Cu doped ZnO self-organized into microspheres The XRD patterns, Scanning electron microscopy and transmission electron microscopy micrographs of doping of Cu in ZnO confirmed the formation of microspheres and indicated that the Cu2+ is successfully substituted into the ZnO host structure of the Zn2+ site Cu doping shifts the absorption onset to blue from 373 to 350 nm, indicating an increase in the band gap from 333 to 355 eV A relative increase in the intensity of the deep trap emission of Cu-doped ZnO is observed when increasing the concentration of Cu Magnetic measurements indicate that Cu-doped ZnO samples are ferromagnetic at room temperature except pure ZnO

Abstract: Conducting polyaniline-stannous oxide (PAni-SnO) composites were synthesized by the in situ polymerization of aniline in the presence of SnO The composites formed were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) As there is a greater need for materials with electromagnetic interference (EMI) shielding properties over a large operating frequency band, the present study highlights the dielectric and EMI shielding response of PAni-SnO composites in the microwave frequency range from 8 to 18 GHz (X and Ku bands) All the computations were based on microwave scattering parameters measured by transmission line waveguide technique The EMI shielding effectiveness (EMI SE), return loss, microwave absorption and dielectric properties of the PAni-SnO composites were evaluated for various wt% of SnO (10, 20, 30, 40 and 50 wt%) in PAni In X-band, the composites exhibits EMI SE in the range −18 to −23 dB, with microwave absorbance of 70–83 % and in the Ku-band, the composites exhibits EMI SE values of −175 to −225 dB with 67–85 % absorbance Our investigations reveal that the PAni-SnO composites are potential candidates for EMI shielding applications for both the X and Ku bands

Abstract: The use of Pb-bearing solders in electronic assemblies is avoided in many countries due to the inherent toxicity and environmental risks associated with lead. Although a number of “Pb-free” alloys have been invented, none of them meet all the standards generally satisfied by a conventional Pb–Sn alloy. A large number of reliability problems still exist with lead free solder joints. Solder joint reliability depends on mechanical strength, fatigue resistance, hardness, coefficient of thermal expansion which are influenced by the microstructure, type and morphology of inter metallic compounds (IMC). In recent years, Sn rich solders have been considered as suitable replacement for Pb bearing solders. The objective of this review is to study the evolution of microstructural phases in commonly used lead free xSn–yAg–zCu solders and the various factors such as substrate, minor alloying, mechanical and thermo-mechanical strains which affect the microstructure. A complete understanding of the mechanisms that determine the formation and growth of interfacial IMCs is essential for developing solder joints with high reliability. The data available in the open literature have been reviewed and discussed.

Abstract: ZnO epitaxial thin films were grown on p-type Si(100) substrates by dual ion beam sputtering deposition system. The crystalline quality, surface morphology, optical and electrical properties of as-deposited ZnO thin films at different growth temperatures were studied. Substrate temperature was varied from 100 to 600 °C at constant oxygen percentage O2/(O2 + Ar) % of 66.67 % in a mixed gas of Ar and O2 with constant chamber pressure of 2.75 × 10−4 mBar. X-Ray diffraction analyses revealed that all the films had (002) preferred orientation. The minimum value of stress was reported to be −0.32 × 1010 dyne/cm2 from ZnO film grown at 200 °C. Photoluminescence measurements demonstrated sharp near-band-edge emission (NBE) was observed at ~375 nm along with deep level emission (DLE) in the visible spectral range at room temperature. The DLE Peak was found to have decrement as ZnO growth temperature was increased from 200 to 600 °C. The minimum FWHM of the NBE peak of 16.76 nm was achieved at 600 °C growth temperature. X-Ray photoelectron spectroscopy study revealed presence of oxygen interstitials and vacancies point defects in ZnO film grown at 400 °C. The ZnO thin film was found to be highly resistive when grown at 100 °C. The ZnO films were found to be n-type conducting with decreasing resistivity on increasing substrate temperature from 200 to 500 °C and again increased for film grown at 600 °C. Based on these studies a correlation between native point defects, optical and electrical properties has been established.

Abstract: As a heat-resistant die attach technology processed at low temperatures, three Ag filler-based sinter joining materials have been proposed. Among these, Ag flake pastes exhibited the greatest potential. Joining was carried out by sintering Ag nanoparticles/flakes in air at 200 °C for 60 min. All of the joined samples survived up to 1,000 thermal cycles in a temperature range from −40 to 180/250 °C with a 30 min dwell time. In particular, the joining strengths with the Ag micron and, Ag nano-thick flake pastes maintained excellent strength. Neither thermal fatigue cracks nor large voids were observed in the Ag sintered layers. Thus, low-temperature and low-pressure sinter joining with Ag flakes is expected to have an application in high power semiconductor devices for ultra-high temperature operation.

Abstract: The size and morphology of intermetallic compounds (IMCs) of Sn–1.0Ag–0.5Cu (SAC105) solder alloys can have a significant influence on the mechanical strength of solder joints. The aim of the present study is to investigate the influence of SiC nano-particles addition on the microstructure, thermal behavior, and corresponding mechanical properties of SAC(105) solder alloys. Results show that the addition of SiC nanoparticles into the SAC(105) alloy melt prompts the formation of primary β-Sn phase with small sub-grain size in the solidified structure. The SiC nanoparticles can offer an additional nucleation sites for the formation of refined Ag3Sn and Cu6Sn5 IMCs. The hard SiC particles and refined IMCs with small spacing could obstruct the dislocation slipping and thus, lead to a strong dispersion strengthening mechanism in the composite solder. As a result, the composite SAC(105)/SiC solder displayed a higher ultimate tensile strength and 0.2 % yield strength (0.2 %YS) than that of plain SAC(105) solder. The addition of SiC nano-sized particles can also effectively reduce the undercooling and pasty range, while the melting temperature is maintained at the SAC(105) level, indicating that the novel composite solder is fit for existing soldering process.

Abstract: Emerging SiC power semiconductor devices are expected to work under the high temperature condition of 250–300 °C while the operation of Si devices is limited up to 180 °C. The die-bonding materials for emerging SiC power devices hence need to have sufficient capability in such extreme operating environments. In this study, we investigated the thermomechanical reliability of the die-attach technology using Ag flake paste, which can be processed by low-temperature and low-pressure sintering. The Ag flakes start to sinter immediately after the organic dispersant layer is removed from the flake surface at 160 °C, and die-bonding consequently becomes possible. The tested Si die-attachments joining with the paste maintained high strength (23 MPa) up to 1,000 thermal cycles from −40 to 180 °C. The stable microstructures without crack and no interfacial debonding assure the reliability of the Ag flake paste die-attach of Si. SiC die-attachments also maintained their high strength (24 MPa) up to 1,000 cycles of −40 and 250 °C, though a slight degradation appeared after 1,000 cycles. The debondings at the sintered Ag flake paste layer/SiC wafer interface were affected to the joining strength with the Ag flake paste. The obtained results indicate that our Ag flake paste die-attach can be applied to both Si and SiC power devices capable of high temperature operations.

Abstract: The mixed spinel-perovskite multiferroic composites of xNiFe2O4-(1 − x)BaTiO3 (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) have been prepared by sol–gel method. The structure and morphology of the composites were examined by means of X-ray diffraction and transmission electron microscope. High-resolution transmission electron microscope image indicates a clear view of ferrite and ferroelectric phase. Moreover, we observed a fine interface between the two phases, where the coupling effect of ferrite and ferroelectric phase happened. The composites show excellent ferromagnetic and ferroelectric properties. The saturation magnetization (Ms) reaches to 24.139 emu/g for x = 0.6 at room temperature, the magnetization is about 2.37 emu/g for x = 0.6 when the temperature decreases to 90 k, and the polarization reaches to 3.75 μC/cm2 for x = 0.1. Frequency dependent variations of dielectric constant and loss tangent for xNiFe2O4-(1 − x)BaTiO3 were studied in detail.

Abstract: The interconnection lengths between the stacked chips in three-dimensional (3D) package are a few of microns, hence the solder joints for the stacked chips joining are mainly composed by intermetallic compounds (IMCs) after reflow processes. To evaluate the phase transformation of Cu–Sn IMCs in the small interconnection joints, the Cu/Sn/Cu structures were bonded with different bonding times at various temperatures in argon gas atmosphere in this study. Scanning electron microscope and energy-dispersive X-ray were used to observe the joint interfacial microstructures and electron back scattering diffraction was used to identify the grain orientations in the joints. Scalloped Cu6Sn5 grains were found to be initially formed on the Cu substrates at the early stage. A lot of small Cu6Sn5 grains formed on the surfaces of the big scallop Cu6Sn5 grains. Those small grains gradually grew up to merge into the big Cu6Sn5 grains. With longer reflow time, the Cu6Sn5 grains initiated at both side of Cu substrate continued to grow up and started to contact with each other. Meantime, the different Cu6Sn5 grains with different grain orientations have merged into some bigger grains. The Cu3Sn grains formed between Cu6Sn5 layers and Cu substrates have further developed at the expense of the depletion of Cu6Sn5. Most of columnar Cu3Sn grains were vertical to Cu substrate surface and their grain sizes were 1–5 μm. With 960 min at 300 °C, the pure Cu3Sn IMC joint has formed. The Cu3Sn grains in IMC joint had different grain orientations and a contact line was observed in the middle of the Cu3Sn IMC joint.

Abstract: Undoped and Doubly (Magnesium + Fluorine) doped zinc oxide (ZnO:Mg:F) thin films with different Mg doping levels (4, 8, 12 and 16 at.%) and constant F doping level (20 at.%) were fabricated by employing a simplified spray pyrolysis technique. The antibacterial and certain physical properties of the films were studied as a function of Mg doping level. All the films exhibited hexagonal wurtzite structure with preferential orientation along the (002) plane. A lesser electrical resistivity was achieved in the present study than earlier reports of ZnO:Mg films thanks to the simultaneous doping of F with Mg in ZnO films. From the optical studies, it was observed that, all the films showed good transparency (≈85 %) with significant enhancement in the optical band gap with Mg doping level. The obtained PL spectra were well corroborated with the structural and optical studies. Further, it was also found that the antibacterial activity of doubly doped ZnO films was enhanced remarkably by the increasing incorporation of Mg concentration.

Abstract: To improve thermoelectric performance, polar-solvent vapor annealing (PSVA) method was introduced into the preparation of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films. The solvent vapors included dimethyl sulfoxide, ethylene glycol, N,N-dimethylformamide, N-methyl-2-pyrrolidone, and deionized water (H2O). The PSVA-treated PEDOT:PSS films exhibited significantly enhanced electrical conductivity and the maximum value was up to 496 S cm−1. Especially, utilizing the PSVA method, H2O could also remarkably enhance the electrical conductivity of pristine PEDOT:PSS film from 0.2 to 57 S cm−1. There was no distinct change for the Seebeck coefficient of PSVA-treated films with the significantly enhanced electrical conductivity, thereby a maximum power factor of 9.47 μW m−1 K−2 at room temperature was obtained. The effects of PSVA method on thermoelectric performance of PEDOT:PSS films were also investigated systematically by analyzing the changes in morphology, carrier mobility and carrier concentration. The results confirmed that PSVA-treated PEDOT:PSS films could obtain smoother morphologies and realize the simultaneous increase of carrier mobility and carrier concentration, which results in the improvement of the thermoelectric performance.

Abstract: In the present work, we have interested to understand the influence of cobalt doping on the various properties of ZnO nanoparticles, a series of samples were successfully synthesized using sol–gel auto-combustion method. The effects of Co doping on the structural and optical properties of ZnO:Co nanoparticles were investigated using X-ray diffraction (XRD), scanning electron microscopy, fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible spectroscopy, photoluminescence spectroscopy and vibrating sample magnetometer (VSM). With the sensitivity of the XRD instrument, the structural analyses on the undoped and Co-doped ZnO samples reveal the formation of polycrystalline hexagonal-wurtzite structure without any secondary phase. FTIR spectra confirm the formation of wurtzite structure of ZnO in the samples. The optical absorption spectra showed a red shift in the near band edge which indicates that Co2+ successfully incorporated into the Zn2+ lattice sites. The room temperature PL measurements show a strong UV emission centered at 392 nm (3.16 eV), ascribed to the near-band-edge emissions of ZnO and defect related emissions at 411 nm (violet luminescence), 449 nm (blue luminescence) and 627 nm (orange-red luminescence), respectively. Magnetic study using VSM reveals that all the samples are found to exhibit room temperature ferromagnetism.

Abstract: Thin films of copper tin sulfide (Cu2SnS3) were obtained by sulfurizing a stack of thin layers of Cu and SnS in nitrogen atmosphere. The film stack was obtained by the sequential electrodeposition of SnS and Cu. The Cu2SnS3 film was characterized for structural, morphological, composition, optical, spectroscopic, and electrical properties. The optimum condition for the formation of Cu2SnS3 was developed after testing different sulfurization temperatures. The films were polycrystalline with monoclinic structure which was confirmed by Raman and transmission electron microscopy analysis. The interplanar spacings estimated from the high resolution transmission electron microscopy images are 2.74, 2.19, and 2.06 A. The average crystallite size is 13 nm, and the band gap of the film is in the range of 1 eV. The surface chemical composition determined by X-ray photoelectron spectroscopy showed the Cu:Sn:S ratio as 1.9:1:2.85 which is close to the stoichiometric Cu2SnS3. The films are p-type, photosensitive, and the conductivity measured in dark was in the range of 4 × 10−3 Ω−1 cm−1. The comprehensive characterization presented in this paper will update the knowledge on this material.

Abstract: In the present work, the effect of annealing temperature on the luminescence and photoconductivity properties of ZnO nanoparticles (NPs) has been investigated. The ZnO NPs have been prepared at low temperature by a simple one step solid state reaction method using ZnSO4·7H2O as a starting precursor. X-ray diffraction results show, the prepared samples have a hexagonal wurtzite structure of ZnO NPs. FE-SEM reveals that the prepared ZnO nanoparticles have perfect spherical shape with little agglomeration. UV–visible absorption spectrum of as-prepared ZnO sample shows an absorbance peak at ~372 nm (~3.32 eV), which is blue shifted as compared to bulk ZnO (~386 nm). The annealed sample exhibits red shift of absorption peak. The photoluminescence spectra of as-prepared sample as well as annealed samples show one emission peak in UV region, and violet, blue, blue-green and green emissions in visible region. The sample annealed at 650 °C results in a significant reduction in luminescence as compared to that of the sample annealed at 450 °C. The photoconductivity properties such as voltage dependence of photocurrent, growth and decay of photocurrent as well as wavelength dependence of photocurrent have been studied in detail.

Abstract: The influences of annealing effects have been explored on the crystallinity, morphology, optical and magnetic properties of Ag–ZnO nanostructures prepared by a simple sol–gel method. X-ray powder diffraction, scanning electron microscope, high resolution transmission electron microscope (HRTEM), vibrating sample magnetometer and photoluminescence spectroscopy (PL) have been used to characterize the crystal structures, surface morphology, magnetic and optical properties of the pure ZnO and Ag–ZnO nanostructures respectively. The synthesized Ag–ZnO nanostructures are found to have hexagonal wurtzite crystal structures and their grain size increases while lattice strain decreases on annealing. From HRTEM observation, it is found that the annealed samples show nanorod like structures with Ag nanoparticles (NPs) embedded on the surface. Due to annealing effect, Ag–ZnO shows higher saturation magnetization at room temperature.

Abstract: Lead-free Ba(Zr0.15Ti0.85)O3 (BZT15) ceramics were synthesized by adopting the solid-state synthesis method. The effect of increasing sintering temperature (Ts) in the range of 1,350–1,450 °C on the microstructure, dielectric, polarization, and electric field induced strain of the ceramics was studied. Fine grained (~260 nm) BZT15 ceramics displayed single phase perovskite structure with relative densities >94 % of the theoretical density. Both grain size and shape were influenced by the sintering parameters. With increase in Ts, not only the maximum dielectric constant decreased from 11,412 to 8,734 along with an increase in the degree of diffuseness, but also interestingly the Curie temperatures were found to vary within an interval of 61–73 °C. Optimum sintering temperature has been found resulting in high remnant polarisation and strain in these ceramics. The properties observed are attributed to a contribution from all polar vectors present in coexistent phases.

Abstract: La3+ ion substituted barium Z-type hexaferrite, Ba3−XLaXCo2Fe24O41 powders (X = 0.0, 0.05, 0.10 and 0.15), have been synthesized using sol gel auto-combustion method. The phase identification, microstructure, complex permittivity, complex permeability and static magnetic properties of the samples were studied using X-ray diffraction, scanning electron microscopy, vector network analyzer and vibrating sample magnetometer. The results revealed that introducing La3+ ion instead of Ba2+ ion led to an obvious enhancement of the electromagnetic properties. The crystallite size of the produced powders was slightly increased with increasing La3+ content. The microstructure of the produced powders appeared as hexagonal-platelet like structure. As the La content increase, the static magnetic properties were increased, the real part of complex permittivity was increased while the imaginary part was decreased. Moreover, the real part of complex magnetic permeability was decreased and the imaginary part was increased. The reasons of the obtained results were discussed on basis of electromagnetic theory.

Abstract: BiFeO3–BTiO3(BF–BT) ceramics as a promising candidate for lead-free high-temperature piezoelectric ceramics were studied with a special emphasis on the compositional dependence of piezoelectric properties. Excess Bi was added to compensate for the evaporation of Bi3+ ions during sintering and this addition was found to be effective in improving the piezoelectric properties of BF–BT ceramics. The microstructure, dielectric and piezoelectric properties of excess Bi doped BF–BT ceramics were investigated. Maximum piezoelectric constant d 33 = 142 pC/N and k p = 0.302 were obtained with 0.04 Bi doping. At the same time, an enhanced Curie temperature T c, 452 °C, was obtained. The combination of improved piezoelectric properties and increased T c makes these ceramics suitable for elevated temperature piezoelectric devices.

Abstract: Barium strontium titanate (BST) Ba1−x Sr x TiO3 nanopowders have been successfully synthesized using oxalate precursor route. The effect of Sr2+ ion content from 0.3 to 0.7 on the crystal structure, crystallite size, microstructure, electrical and optical properties was systematically studied. The results revealed that well crystalline single BST phase was formed by annealing the oxalate precursor at 1,000 °C for 2 h. The crystallite size of the BST powders was decreased with increasing the Sr2+ ion molar ratios. The crystallite size was decreased from 56.0 to 33.1 nm when the Sr2+ ion content increased from 0.3 to 0.7. Additionally, the lattice parameter (a), unit cell volume and X-ray density of BST ware decreased whereas the porosity, % were increased with Sr2+ ion concentration. The BST phase appeared as cubic-like structure. The spectrophotometer measurement results demonstrated that the room temperature band gap energy varied with the Sr2+ ion composition x. The band gap energy was shifted to low energy and it was decreased from 3.6 to 3.2 eV with increasing the Sr2+ ion content from 0.3 to 0.7. Moreover, the DC resistivity was enhanced with increasing the Sr2+ ion ratio. The dielectric response obtained for the stressed samples corresponds to a true resonance rather than a dispersion process with a characteristic frequency around 1 GHz at room temperature. However, the peaks commonly observed at GHz frequency were changed with varying the Sr2+ ion composition. The high imaginary components of dielectric permittivity for x = 0.3 was found at higher frequency region around 1.6 GHz compared with the samples with x values of 0.5 and 0.7 in which the frequency regions were around 1.25 and 1.15 GHz, respectively.

Abstract: Silicon carbide (SiC) thin films were deposited using hot wire chemical vapor deposition technique from silane (SiH4) and methane (CH4) gas precursors. The effect of deposition pressure on structural and optical properties of SiC films was investigated. Various spectroscopic methods including Fourier transform infrared spectroscopy, Raman scattering spectroscopy, Auger electron spectroscopy, and UV–Vis–NIR spectroscopy were used to study these properties. Films deposited at low deposition pressure were Si-rich, and were embedded with nano-crystals of silicon. These films showed strong absorption in the visible region and had low energy band gaps. Near stoichiometric SiC film, were formed at intermediate deposition pressure and these films were transparent in the visible region and exhibited a wide optical band gap. High deposition pressures caused inhomogeneity in the film as reflected by the increase in disorder parameter and low refractive index of the films. This was shown to be due to formation of sp 2 carbon clusters in the film structure.

Abstract: Ni doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Ni:Zn atomic ratio from 0 to 5 %. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and nickel acetate tetrahydrate followed by heat treatment at 65 °C under refluxing using methanol as a solvent. X-ray diffraction analysis reveals that the Ni-doped ZnO crystallizes in a wurtzite structure with crystal size of 4–11 nm. These nanocrystals self-aggregated themselves into hollow spheres of size of 600–170 nm. High resolution transmission electron microscopy image shows that each sphere is made up of numerous nanoparticles of average diameter 4 nm. The XRD patterns, Scanning electron microscopy and transmission electron microscopy micrographs of doping of Ni in ZnO are confirmed the formation of micro-spheres. Furthermore, the UV–vis. spectra and photoluminescence spectra of the Ni-doped ZnO nanoparticles were also investigated. The band gap of the nanoparticles can be tuned in the range of 3.55–3.36 eV by the use of the dopants. The observed red shift in the band gap from UV–visible analysis and near band edge UV emission with Ni doping may be considered to be related to the incorporation of Ni ions into the Zn site of the ZnO lattice.

Abstract: Nickel oxide (NiO) sensor films were prepared on glass substrate by a sol–gel spin coating technique. These films were characterized for their structural and morphological properties by means of X-ray diffraction, field emission scanning microscopy and atomic force microscopy. The NiO films are oriented along (200) plane with the cubic crystal structure. These films were utilized in nitrogen dioxide gas (NO2) sensor. The dependence of the NO2 response on operating temperature, NO2 concentration was investigated. The NiO film showed selectivity for NO2 over Cl2 compared to H2S $$ \left( {{\text{S}}_{{{\text{NO}}_{ 2} }} /{\text{S}}_{{{\text{Cl}}_{ 2} }} = 3 7. 5,{\text{ S}}_{{{\text{NO}}_{ 2} }} /{\text{S}}_{{{\text{H}}_{ 2} {\text{S}}}} = 3. 4} \right) $$ . The maximum NO2 response of 23.3 % with 85 % stability at gas concentration of 200 ppm at 200 °C was achieved. The response time of 20 s and recovery time of 498 s was also recorded with same operating parameters.

Abstract: This study reports the effect of Lu addition on the microstructural and superconducting properties of YBa2LuxCu3O7−δ (Y123) superconducting samples with x = 0, 0.1, 0.3, 0.5 and 0.7 by means of X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), electron dispersive X-ray (EDX), electrical resistivity and transport critical current density (Jc) measurements. The samples prepared by the liquid ammonium nitrate and derivatives are exposed to various annealing time (20, 40 and 60 h) and temperature (950, 960 and 970 °C), and the best ambient for the sample fabrication is determined to be 970 °C for 20 h. Zero resistivity transition temperatures (Tc), critical current densities (Jc), variation of transition temperatures, hole-carrier concentration, grain size, lattice parameter, surface morphology, element distribution, crystallinity and resistivity (at room temperature) values of the bulk superconducting samples prepared at 970 °C for 20 h are compared with each other. Tc and Jc values of the samples are inferred from the dc resistivity and the critical current measurements, respectively. The results show that the Tc value of the pure sample is about 90.6 K while the sample doped with 0.1 wt% Lu has the maximum Tc value (92.5 K). However, beyond x = 0.1, the Tc value is observed to decrease toward to 83.5 K with increment in the Lu addition. Similarly, the Jc values measured are found to reduce from 142 to 76 A/cm2 with the addition. Moreover, XRD measurements show that both pure and Lu-doped samples exhibit the polycrystalline superconducting phase with the changing intensity of diffraction lines and contain Y123 and Y211 phase, confirming the incorporation of Lu atoms into the crystalline structure of the samples studied. At the same time, comparing of the XRD patterns of samples, the intensity ratio of the characteristic (110) and (013) peaks on the sample doped with 0.1 wt% Lu is more than that on the other samples prepared. Additionally, SEM images display that the sample doped with 0.1 wt% Lu obtains the best crystallinity, grain connectivity and largest grain size whereas the worst surface morphology is observed for the maximum doped sample (x = 0.7). Further, EDX results demonstrate that the Lu atoms doped are successfully introduced into the microstructure of the Y123 samples studied and the maximum Cu element level is observed for the sample doped with 0.1 wt%, explaining that why this sample obtains the best superconducting properties compared to others. According to all the results obtained, it is concluded that the 0.1 wt% Lu addition into the Y123 system improves the microstructural and superconducting properties of the samples studied.

Abstract: Pure and Tb-doped ZnO nanoparticles have been synthesized by chemical co-precipitation method. The transmission electron microscopy study reveals the spherical morphology of synthesized nanoparticles with average particle size 14–18 nm. The effect of Tb-doping on structural, optical and magnetic properties has been studied. X-ray diffraction shows that pure and Tb-ZnO nanoparticles exhibit wurtzite structure having hexagonal phase with primitive unit cell. It further reveals that there is no effect of Tb-doping on the X-ray diffraction pattern up to 2 % doping, however, higher doping concentration result in accumulation of Tb on ZnO surface. Photoluminescence spectra reveal that the doping Tb in ZnO changes crystallographic structure generating non-radiative oxygen vacancies. Three emission peaks located around 423, 485 and 515 nm has been observed. Pure ZnO nanoparticles show diamagnetic character, however, Tb-doped ZnO nanoparticles exhibit room temperature ferromagnetism. The correlation between defects generated upon Tb-doping to the observed ferromagnetism, in the synthesized nanoparticles, has been reported.

Abstract: The microwave dielectric properties and the microstructures of (1 − x)Mg2SiO4–xCaTiO3 composite ceramics with Bi2O3–Li2CO3–H3BO3 (BLB) additions prepared by solid-state reaction method have been investigated. The crystalline phases were studied systematically by using the X-ray diffraction, microstructures by the scanning electron microscopy and composition analysis by the energy-dispersive spectroscopy. The results showed that the τ f of (1 − x)Mg2SiO4–xCaTiO3 was related to the amount of CaTiO3 phase constitutions. When x = 0.08 and 0.09, the τ f of (1 − x)Mg2SiO4–xCaTiO3 were about −3.0 ppm/°C and +6.8 ppm/°C. The microwave dielectric properties of 0.91Mg2SiO4–0.09CaTiO3 ceramics samples with BLB additions sintered at 900–1,000 °C were characterized, and the permittivity and Q × f were associated with the amount of BLB and the sintering temperature. The sintering temperature of ceramics was reduced to 950 °C from about 1,250 °C and the temperature coefficient of resonant frequency (τ f ) was modified to −5.0 ppm/ °C with good Q × f. The addition of 12.0 wt% Bi2O3–Li2CO3–H3BO3 in 0.91Mg2SiO4–0.09CaTiO3 ceramics sintered at 950 °C showed excellent dielectric properties of e r = 7.7, Q × f = 11,300 GHz (f = 6.1 GHz) and τ f = −5.0 ppm/ °C. This represented a very promising candidate material for LTCC applications.