Showing papers in "Journal of Materials Science: Materials in Electronics in 2010"

Inkjet printed electronics using copper nanoparticle ink

Abstract: Inkjet printing of electrode using copper nanoparticle ink is presented. Electrode was printed on a flexible glass epoxy composite substrate using drop on demand piezoelectric dispenser and was sintered at 200 °C of low temperature in N2 gas condition. The printed electrodes were made with various widths and thickness. In order to control the thickness of the printed electrode, number of printing was varied. Resistivity of printed electrode was calculated from the cross-sectional area measured by a profilometer and resistance measured by a digital multimeter. Surface morphology of electrode was analyzed using scanning electron microscope (SEM) and atomic force microscope (AFM). From the study, it was found that 10 times printed electrode has the most stable grain structure and low resistivity of 36.7 nΩ m.

A review on the interfacial intermetallic compounds between Sn–Ag–Cu based solders and substrates

Abstract: The objective of this review is to study the interfacial intermatallic compounds (IMCs) between Sn–Ag–Cu based solders and common substrates, which play a crucial role in solder joints typically present in Pb-free electronics manufacturing. The microstructural evolution of IMCs at the solder/substrate interfaces is analyzed, while the models and theories describing the formation/growth mechanism of interfacial IMCs are also introduced. We focus on the influence of a variety of factors that have been reported recently, including substrates, minor alloying, mechanical stress, electromigration and thermomigration etc., as full understanding of the mechanisms that determine the formation and growth of interfacial IMCs is important to reach for developing high reliability solder joints. In the end of this review, the characteristics of the IMCs are compared and illustrated, which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints.

Structural, optical and magnetic characterization of Cu-doped ZnO nanoparticles synthesized using solid state reaction method

Abstract: Polycrystalline undoped and Cu-doped Zinc oxide (Zn0.98Cu0.02O) nanocrystals were successfully synthesized by solid-state reaction method. The micro structural, optical and magnetic properties have been characterized using powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive analysis using X-rays (EDAX), UV–Visible spectroscopy, Photoluminescence, Vibrating sample magnetometer and Electron paramagnetic resonance spectroscopy. XRD pattern reveals that the samples possess hexagonal wurtzite structure of ZnO without any secondary phase after copper doping. Optical absorption analysis of the samples showed a red shift in absorption band edge with copper doping in ZnO. Photoluminescence spectra of the samples shows prominent peaks corresponding to near band edge UV emission and defect related green emission in the visible region at room temperature and their possible mechanism have also been discussed. Magnetic measurements using VSM showed that the nanocrystalline copper doped ZnO exhibits ferromagnetic behaviour at 300 K. EPR analysis also confirms the substitution of Zn site by Cu2+.

Development of Sn–Zn lead-free solders bearing alloying elements

Abstract: Sn–Zn solder alloys have been considered as one of the more attractive lead-free solders since it can easily replace Sn–Pb eutectic alloy without increasing the soldering temperature. However, there are still some problems to be resolved, such as the argument about the poor oxidation resistance and embrittlement behavior. In order to overcome these drawbacks, and further enhance the properties of Sn–Zn lead-free solder alloys, a small amount of alloying elements (rare earths, Bi, Ag, Al, Ga, In, Cr, Cu, Sb, Ni, Ge) added into Sn–Zn alloys were selected by many researchers. For example, a small amount of Al, P, Bi, Ga can improve the high-temperature oxidation resistance of Sn–Zn solders remarkably as well as Cr. This paper summarizes the effects of alloying elements on the wettability, oxidation resistance, melting behavior, mechanical properties, creep properties, microstructures and intermetallic compounds layer of Sn–Zn lead-free solders.

High efficient ultraviolet photocatalytic activity of BiFeO3 nanoparticles synthesized by a chemical coprecipitation process

Abstract: Single-crystalline BiFeO3 nanoparticles have been synthesized through a simple chemical coprecipitation process using bismuth and iron nitrates. By employing both X-ray diffraction and electron diffraction, the nanoparticles were unambiguously identified to have a rhombohedrally distorted perovskite structure. X-ray photoelectron spectroscopy investigation shows that Fe element exists as the Fe3+ valence state in the BiFeO3 nanoparticles. UV–Vis absorption spectrum indicates that the absorption cut-off wavelength of the nanoparticles is about 580 nm, corresponding to the energy bandgap of 2.10 eV. The BiFeO3 nanoparticles exhibited an efficient ultraviolet photocatalytic activity, more than 92% of methyl orange was decolorized after 260 min UV irradiation. Unexpectedly, the BiFeO3 nanoparticles do not show any efficient visible light photocatalytic activity, although the nanoparticles absorb visible light in the wavelength range of 400–580 nm.

Orthogonal analysis for perovskite structure microwave dielectric ceramic thin films fabricated by the RF magnetron-sputtering method

Abstract: The perovskite structure microwave dielectric ceramic thin films have been deposited by radio frequency (RF) magnetron sputtering on SiO2(110) substrates. Subsequently, orthogonal analysis has been adopted to optimize the process parameters. The experimental results indicate that sputtering pressure has the greatest impact on comprehensive evaluation indicators such as the film quality, whereas sputtering power has a lower effect; the ratio of O2/Ar and substrate temperature have the least impact on the process. Thus, the optimal process parameters to prepare perovskite structure dielectric thin films by RF magnetron sputtering are as follows: 200 W of sputtering power, 0.25 Pa of sputtering pressure, Ar as working gas, and substrate temperature of 610 °C.

A study of the growth mechanism of CVD-grown ZnO nanowires

Abstract: ZnO nanowires were grown by CVD process using both pure Zn powder and a mixture of ZnO and graphite powders as the Zn source, and the key factors controlling nanowire growth were identified. In both processes, the partial pressure of zinc vapor determines the prevailing growth morphology and is sensitive to the growth conditions. In the case of Zn powder as the source, the predominant growth mechanism is driven by self-catalyzed growth on the Si substrate, and in the case of a mixture of ZnO and graphite used as the source, the formation of ZnO nanowires is controlled by the vapor–liquid-solid mechanism, where the gold particles serve as catalyst.

Effect of Mn doping on the dielectric properties of BaZr0.2Ti0.8O3 ceramics

Abstract: Pure and Mn-doped BaZr0.2Ti0.8O3 ceramics are prepared via the conventional solid state reaction method. The microstructures, dielectric properties, and diffuse transition of Mn-doped BaZr0.2Ti0.8O3 ceramics have been investigated. The results indicate that manganese ions enter the unit cell maintaining the perovskite structure of solid solution. The addition of manganese leads to the decrease of the Curie temperature. The dielectric loss of the Mn-doped BZT ceramics is lower than that of pure BZT ceramics, and decreases as Mn content increases. The diffuseness of the phase transition of Mn-doped BZT ceramics decreases with the increase of Mn content. There is no obvious frequency dispersion around the dielectric constant peaks for Mn-doped BZT ceramics. The coercive electric field and the remanent polarization decreases as Mn content increases.

Structural and electrical studies of nano structured Sn1−x SbxO2 (x = 0.0, 1, 2.5, 4.5 and 7 at%) prepared by co-precipitation method

Abstract: SnO2 semiconducting nanopowders doped with antimony Sn1−x Sb x O2 (x = 0.0, 1, 2.5, 4.5 and 7 at%) was achieved by co-precipitation method. TG/DTA and FT-IR studies revealed the removal of organic residuals in the precursor leading to the formation of oxides during calcinations process. A change in color from white to bluish occurred on calcinations of the powder at 500 °C in air. The distortion ratio, strain and particle size were measured from X-ray diffraction (XRD) spectra and their changes with dopants concentration were determined. Transmission electron microscopy (TEM) images support to conform the particle size. The electrical resistivity and activation energy of the ATO particles decreases as compared with pure SnO2, due to the incorporation of on Sn4+ ions by as Sb5+ ion in the host SnO2 matrix. Incorporation of Sb5+ was evidenced through the XPS spectrum.

Investigation of rare earth-doped BiAg high-temperature solders

Abstract: In the present work, the microstructure and properties of the rare earth Ce-doped BiAg solders with various Ag content are investigated. The results indicate that the maximum of the shear strength appears in the BiAg solder joints containing 5 and 7.5 wt.% Ag. At the same time, a similar trend appears in the hardness test of the BiAg bulk solders. Moreover, the results show that the microstructure and properties of the solders can be modified due to the unique properties of rare earth element. Small amounts of rare earth addition may enhance the wettability of SiAg solder on Cu substrate, and result in the increase of the shear strength of the solder joints. However, the rare earth addition may not give obvious influence on the melting temperature and the electrical conductivity. Thus, it is expected that the BiAg solder containing small amounts of rare earth element may possess a better potential as a replacement for high-Pb solders.

Effects of trace rare earth Nd addition on microstructure and properties of SnAgCu solder

Abstract: Effects of rare earth Nd on solderability of the Sn38Ag07Cu alloy were studied by wetting balance method, and the mechanical properties (such as pull-force and shear-force) of the joints soldered with SnAgCu–XNd solders were determined using STR-1000 joint strength tester Moreover, the microstructures of SnAgCu–XNd solders bearing different amount of Nd as well as the intermetallic compounds (IMCs) formed at solder/Cu interface during soldering have been investigated using optical microscopy, scanning electron microscopy and energy dispersive X-ray analysis, respectively The results indicate that trace amount of Nd addition can remarkably improve the solderability and mechanical properties of SnAgCu solder At the same time, it is found that rare earth Nd in SnAgCu solder could refine and improve microstructure of the solder, some bigger IMC plates in SnAgCu solder were replaced by fine granular IMCs Moreover, the thickness of the intermetallic layer at the Cu/solder interface was reduced significantly In summary, we suggest that the most suitable content of rare earth Nd is about 005 wt% and it will be inadvisable when the Nd exceeds 025 wt%

ZrO2 thin films on Si substrate

Abstract: In the advancement of metal–oxide–semiconductor technology, Si-based semiconductor, with SiO2 as outstanding dielectric, has been dominating microelectronic industry for decades. However, the drastic down-scaling in ultra-large-scale integrated circuitry has made ultrathin SiO2 (~1.2 nm) unacceptable for many practical reasons. Introduction of ZrO2 as high-κ dielectrics replacing SiO2 is undeniably a potential yet formidable solution for the aforementioned problem. The objective of this review is to present the current knowledge of ZrO2 thin film as gate dielectric on Si, in terms of its material and electrical properties produced by various deposition techniques. One of the techniques being focused is thermal oxidation of sputtered Zr and the mechanisms of transforming the metal into oxide has been extensively reviewed.

Effect of silver nanostructures on the resistivity of electrically conductive adhesives composed of silver flakes

Abstract: Silver flakes are the most widely applied conductive fillers in electrically conductive adhesives (ECAs) because of their high conductivity and stable chemical properties. It is expected that there are advanced ECAs with both high electrical conductance and good adhesive strength. The high filler loadings can improve the conductance of ECAs, whereas the adhesive strength is decreased. Silver nanostructures are incorporated for the purpose of electrical conductance and adhesive strength improvement of ECAs. A simple method has enabled the synthesis of silver nanostructures by reducing silver nitrate with ethylene glycol in the presence of poly(N-vinylpyrrolidone). They are added to ECAs by dispersing them in ethanol while it is used as the diluent to adjust the volatility of ECAs, preventing them from the aggregation. This proposed process offers the possibility to effectively use silver nanostructures for improving the conductivity of ECAs at the low content of conductive fillers while good adhesive strength may be obtained.

Structural and magnetic properties of nanocrystalline Mg–Cd ferrites prepared by oxalate co-precipitation method

Abstract: Polycrystalline spinel ferrites with general formula Mg1−x Cd x Fe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by oxalate co-precipitation method using high purity sulfates. The samples were sintered at 1,050 °C for 5 h. The structural properties of these samples were investigated by XRD, SEM and FTIR techniques. The X-ray diffraction analysis confirms the formation of single phase cubic spinel structure of all the samples. The lattice constant, X-ray density, physical density, porosity, crystallite size, site radii (r A, r B), bond length (A–O, B–O) on tetrahedral (A-site) and octahedral (B-site) were calculated for the samples. The lattice constant increases with increase in Cd2+ content. The X-ray density increases with increase in Cd2+ content. The crystallite size calculated by Scherrer formula is in the range of 27.79–30.40 nm. Physical densities are calculated by Archimedes principle. The SEM study shows that the grain size increases with increasing Cd2+ content. The FTIR spectra shows two strong absorption bands around 576 and 431 cm−1 on the tetrahedral and octahedral sites, respectively. The dependence of saturation magnetization on Cd2+ content suggests that A–B and B–B super exchange interaction are comparable in strength. Neel’s two sub lattice model is applicable up to x ≤ 0.4, while Y–K three sub lattice models (canted spin) is predominant for x ≥ 0.4.

Effect of post annealing on structural and optical properties of ZnO thin films deposited by vacuum coating technique

Abstract: We report the effect of annealing temperature on structural, electrical and optical properties of polycrystalline zinc oxide thin films grown on p-type silicon (100) and glass substrates by vacuum coating technique. The XRD and AFM measurements confirmed that the thin films grown by this technique have good crystalline hexagonal wurtzite structures and homogenous surfaces. The study also reveals that the rms value of thin film roughness increases from 6 to 16 nm, the optical band gap increases from 3.05 to 3.26 eV and resistivity from 0.3 to 5 Ωcm when the post-deposition annealing temperature is changed from 400 to 600 °C. It is observed that ZnO thin film annealed at 600 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.

Effect of lithium magnesium zinc borosilicate glass addition on densification temperature and dielectric properties of Mg2SiO4 ceramics

Abstract: Mg2SiO4 (Forsterite) ceramics were synthesized by solid state route. The effect of lithium magnesium zinc borosilicate (LMZBS) glass addition on the densification temperature and microwave dielectric properties of forsterite ceramics was investigated. The crystal structure and microstructure of ceramic–glass composites were studied by X-ray diffraction and scanning electron microscopic techniques. The dielectric properties of the sintered samples were measured in the microwave frequency range by the resonance method. Addition of 0.5 wt% LMZBS glass improved densification with e r = 7.3 and Qxf = 121,200 GHz. Addition of 15 wt% LMZBS glass lowered the sintering temperature to about 950 °C with e r = 6.75 and Qxf = 30,600 GHz. The reactivity of 15 wt% LMZBS glass added forsterite with silver was also studied. The result shows that forsterite doped with suitable amount of LMZBS glass is a possible material for LTCC and microwave substrate applications.

Effect of Y 2 O 3 particles on microstructure formation and shear properties of Sn-58Bi solder

Abstract: In the present study, varying weight percentages of Y2O3 particles (3–5 μm) from 0 to 3% were incorporated into eutectic Sn-Bi solder matrix to form composite solders. It is found that the reinforcement particles were well dispersed in the solder matrix. They depressed the growth of intermetallic compound (IMC) layers and reduced the size of IMC grains. Since the Y2O3 particles serve as additional nucleation sites for the formation of primary Bi-rich phase, the size of both Bi-rich phase and the IMCs were decreased gradually with the Y2O3 content increasing. Shear tests were also conducted on as—soldered joints. The growth of solid-state intermetallic compounds layer was examined by thermal aging of the solder/Cu couple for a temperature range from 60 to 120°C and time periods from 50 to 500 h. Compared with Sn-58Bi solder, finer eutectic microstructures were obtained with Y2O3 addition after long time aging. The apparent activation energies calculated for the growth of the intermetallic compound layers were 72 ± 5 kJ/mol of Sn-58Bi, 74 ± 4 kJ/mol of Sn-58Bi-0.5wt%Y2O3, 81 ± 5 kJ/mol of Sn-58Bi-1wt% Y2O3 and 81 ± 7 kJ/mol of Sn-58Bi-3wt.% Y2O3, respectively.

FTIR and Raman spectroscopic investigation of some strontium–borate glasses doped with iron ions

Abstract: Structural investigation of xFe2O3·(100 − x)[3B2O3·SrO] glass system, with 0 ≤ x ≤ 40 mol%, was performed by means of X-Ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies The purpose of this work was to investigate the structural changes that appear in the 3B2O3·SrO glass matrix with the addition and increasing of iron ions content The XRD pattern for the prepared samples shows that vitreous phase is present only for x ≤ 40 mol% For sample containing 50 mol% Fe2O3 was evidenced the presence of a unique crystalline phase, Fe2O3, embedded in an amorphous matrix FTIR data show that BO3 and BO4 are the main structural units of the glass system and the iron ions are located in the network The Raman spectrum of glass matrix indicates a structure with several borate groups (di-, meta-, pyro-borate, etc) In higher concentrations the iron ions break the regulate glass network and determines the appearance of BO4 isolated units

Copper pillar bump design optimization for lead free flip-chip packaging

Abstract: The interfacial delamination between the under bump metallurgy and the aluminum (Al) pad was observed in a copper (Cu) pillar bump evaluation in the work. The finite element analysis was employed to investigate the failure mechanism and the cu pillar bump geometry designed optimization. The finite element simulation result shows that the Cu pillar bump sustains the largest tensile stress at the temperature cycling test. The larger diameter Cu pillar bump can reduce the tensile stress significantly at the high temperature stress environment. Besides, an experiment confirms the finite element simulation result. Furthermore, an underfill with high glass transition temperature (T g) and high modulus also improve the flip-chip ball grid array packaging reliability.

Synthesis and DSC study on Sn3.5Ag alloy nanoparticles used for lower melting temperature solder

Abstract: The traditional Sn–Pb eutectic solder alloys are being phased out from the electronics industry due to the toxicity of lead (Pb), leading to the development and implementation of lead-free solders. Sn3.5Ag lead-free solder alloy, considered to be one of the promising alternatives to replace the traditionally used Sn–Pb solder, however, still has some weaknesses, such as its higher melting temperature than that of the Sn–Pb solder alloy. A possible way to decrease the melting temperature of a solder alloy is to decrease the alloy particle size to the nanometer range. Sn3.5Ag nanoparticles with different size distribution were synthesized using chemical reduction method by applying NaBH4 as reduction agent. The melting properties of these synthesized nanoparticles were studied by differential scanning calorimetry (DSC), and size-dependent melting temperature depression of these nanoparticles has been observed. Gibbs–Thomson equation was used to analyze the size-dependent melting temperature property, giving a good prediction of the melting temperature depression for the Sn-based lead-free solder alloy nanoparticles.

Structural investigations of some bismuth-borate-vanadate glasses doped with gadolinium ions

Abstract: X-ray diffraction (XRD), Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopies have been employed to investigate the xGd2O3 · (95 − x)[2Bi2O3 · B2O3] · 5V2O5 glass system, with 0 ≤ x ≤ 25 mol%. The glass samples have been prepared by melting at 1,100 °C for 10 min followed by rapid cooling at room temperature. The structure of samples was analyzed by means of XRD. The pattern obtained did not reveal any crystalline phase in the samples up to 25 mol%. FTIR spectroscopy data suggest that the gadolinium ions play the network modifier role in the studied glasses. These data show that the glass network consists of BiO3, BiO6, BO3, BO4, and VO4 structural units. The FTIR data show that a conversion among these units takes place and this process mainly depends on the Gd2O3 content. The EPR spectra of the studied glasses exhibit three important features with effective g-values of ≈5.9, 2.85, 2.0 and a weaker feature at g eff ≈ 4.8. For low Gd2O3 contents (x ≤ 10 mol%), the EPR spectra have the typical ‘‘U’’-type shape. For higher contents of Gd2O3 (x > 10 mol%), the spectral features are broadened and finally are dominated by a single broad absorption line located at g eff ≈ 2.0. This broad EPR line is associated to the Gd3+ ions present predominantly as clustered species.

Preparation and charge transport studies of chemically synthesized polyaniline

Abstract: Polyaniline doped with p-toluenesulfonic acid was synthesized using in situ chemical oxidation method for optimization of synthesis parameters. For p-toluenesulfonic acid/aniline molar ratio of 5, the obtained polymer exhibits highest value of the electrical conductivity. The electrical conductivity of polyaniline doped with p-toluenesulfonic acid was measured in the temperature range of 30–300 K. The conductivity of polyaniline was found to increase with rise in the temperature. The measured conductivity versus temperature data was fitted with Arrhenius model, variable range hopping (VRH) model and Kivelson model in order to investigate the charge transfer mechanism in polyaniline. It is shown that conductivity observed over wide temperature range of 30–300 K follows Kivelson model obeying power law behavior.

Structural, optical and electrical studies on nanocrystalline tin oxide (SnO2) thin films by electron beam evaporation technique

Abstract: Nanocrystalline tin oxide (SnO2) thin films were coated using electron beam evaporation technique on glass substrates. To study the gleaming out look of the structure and surface morphological changes, the films were annealed in the temperature 350–550 °C for 1 h. The annealed films were subjected to X-ray diffraction (XRD) and atomic force microscopy (AFM) studies. The XRD patterns of SnO2 thin films as-deposited and annealed at 350 °C illustrate that the films were amorphous, and beyond 350 °C and thereafter they became polycrystalline with tetragonal structure. The crystallite size of the annealed films, obtained through the XRD analysis, increased with the increasing annealing temperature, and it was found to be from 3.6 to 12 nm. The photoluminescence (PL) studies on these films were also carried out. The origin of luminescence was assigned to the defects of the nanocrystalline SnO2 films. The Optical studies (UV-VIS) were performed and the optical band gab energy (Eg) calculations, the dependence of absorption coefficient on the photon energy at short wavelengths, were found to be increasing from 3.65 to 3.91 eV is also investigated.

Preparation and characterizations of tungsten oxide electrochromic nanomaterials

Abstract: Nanoscaled tungsten oxide thin films were fabricated by galvanostatic electrodeposition. The effect of preparation parameters such as tungsten ions concentration, pH, current density and annealing on the properties and performance of WO3 thin films electrochromic materials was investigated. XRD, SEM–EDS, TEM, FTIR, UV–VIS spectrophotometry, and electrochemical measurements were utilized to characterize the structural and compositional properties as well as the electrochromic behaviour of the prepared thin films. Triclinic WO3 structure was prepared at 0.1 M W+ and current density of 0.5 mA cm−2, while at 0.2 M W+ and 1 mA cm−2, orthorhombic structure was revealed. High energy gap of 3.5 eV with diffusion coefficient of 6.81 × 10−11 cm2 S−1 and coloration efficiency of 62.68 cm2 C−1 were obtained for the films prepared at pH 2, 1 mA cm−2, and 0.1 M W+.

Structural and electrical properties of fritless Ni(1−x)CuxMn2O4 (0 ≤ x ≤ 1) thick film NTC ceramic

Abstract: Spinel structured NTC thermistor Ni(1−x)CuxMn2O4 (0 ≤ x ≤ 1) ceramics was prepared by oxalic precursor method and fritless thick films screen printed on alumina. The composition dependent structural and electrical properties are reported in this paper. The results show that with increasing copper ion substitution both Cu2+ and Mn4+ predominantly occupy the octahedral site. The concentration of Cu2+ ions in octahedral site increases while that of Ni2+ ions decreases linearly. The thick film Ni(1−x)CuxMn2O4 ceramic comply with Arrhenius equation. A thermistor constant of ~1,200 K has been obtained for fritless thick film NTC ceramics using inorganic binders in the RT/90 thermal range.

Cobalt: a universal barrier metal for solderable under bump metallisations

Abstract: Published data augmented by new work suggests that cobalt is a suitable constituent of many under bump metallisations, its function being as the barrier metal. This stems from the combination of cobalt’s high wettability by and low solubility in, molten solders, together with the slow rate of growth and favourable mechanical properties of the interfacial intermetallic compounds formed. Although other metals and alloys exhibit similar characteristics, the range of compatible solders is always limited. Cobalt appears to be suitable for use with low melting point bismuth- and indium-based filler metals, lead–tin eutectic, lead-free and high melting point lead-based alloys, as well as the gold-rich solder family.

Effect of praseodymium on the microstructure and properties of Sn3.8Ag0.7Cu solder

Abstract: Effects of Pr addition on wettability, microstructure of Sn3.8Ag0.7Cu solder were studied, the mechanical properties of solder joints were investigated and the fracture morphologies were also analyzed in this paper. The results indicate that adding appropriate amount of Pr can evidently improve the wettability of solder, and it is also found that Pr can refine the β-Sn dendrites and reduce the intermetallic compounds growth inside the solder due to the fine PrSn3 particles formed in the solder which can act as heterogeneous nucleation sites. Moreover, the joints soldered with the SnAgCuPr solders possess sound mechanical properties which may result from the finer microstructure improved by the Pr.

Low temperature synthesis of sol–gel derived Al-doped ZnO thin films with rapid thermal annealing process

Abstract: A series of sol–gel derived Al-doped ZnO (AZO) thin films with rapid thermal annealing process at low temperature were studied to examine the influence of annealing temperature and the Al doping concentration on their microstructure, electrical and optical transport properties. Crystalline AZO thin films were obtained following an annealing process at temperatures between 400 and 600 °C for 10 min in argon gas ambient. AZO thin films with Al doping of 1 at% were oriented more preferentially along the (002) direction, and have larger grain size and lower electrical resistivity, while the highest average optical transmittances of 92% were observed in AZO films with Al doping of 2 at%. With the annealing temperature increasing from 400 to 600 °C, the grain size of AZO films increased, the optical transmittance became higher, and the electrical resistivity decreased to a lowest value of 1.2 × 10−4 Ω cm resulting from the increase of the carrier concentration and the mobility.

Saturation magnetization and structural analysis of Ni0.6Zn0.4NdyFe2−yO4 by XRD, IR and SEM techniques

Abstract: Compositions having general formula Ni0.6Zn0.4Nd y Fe2−y O4 (where y = 0, 0.01, 0.02 and 0.03) were prepared by oxalate co-precipitation method from high purity sulphates. The samples were characterized by XRD, IR and SEM techniques. X-ray diffraction measurements confirmed the formation of single phase cubic spinel structure. Lattice constant increases with rise in Nd3+ content and obeys Vegard’s law. Crystallite size of the samples lies in the range 29.98–31.15 nm. The IR spectra shows two strong absorption bands in the frequency range 400–600 cm−1. Further, it shows that Nd3+ occupies B-site. SEM studies show that the grain size of the samples decreases with increase in Nd3+ content. Saturation magnetization of Nd3+ substituted Ni–Zn ferrites is higher than unsubstituted ferrite.

Nanocrystalline ZnO thin films: optoelectronic and gas sensing properties

Abstract: Nanocrystalline Zinc oxide thin films have been deposited by sol–gel spin coating technique and then have been analyzed before and after a suitable thermal annealing in order to test their applications in various reducing and oxidizing gases. ZnO thin films were highly sensitive and selective for NH3 gas. The spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of zinc oxide thin films. The structure and the morphology of such material have been investigated by high resolution electron microscopy and small area electron diffraction. The average particle size is in 60–70 nm.