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Papers by Shahzad Naseem

In-Plane Semiconductor Lasers V, 2001

ABSTRACT A simple tunable laser structure with quasi-continuous tuning range of 15 nm, more than ... more ABSTRACT A simple tunable laser structure with quasi-continuous tuning range of 15 nm, more than 30 dB side mode suppression ratio, 400 kHz linewidth and low variation in output power over the tuning range is demonstrated. The device involved minor modifications to a standard Fabry Perot (FP) laser and measurements have confirmed modeled predictions. Prototype fabrication has used focussed ion beam etching to generate three reflection/scattering sites with power reflectivity of approximately 1%, at precise locations along the optical axis of a 1500 nm FP laser. The device contact was electrically split at these reflection/scattering sites, thereby generating weak FP cavities within a strong primary FP cavity. Tuning is achieved by precisely changing the currents to each section and hence altering the refractive indices.

Journal of Sol-Gel Science and Technology, 2009

Abstract Flurbiprofen loaded PCL/PVP blend micro-spheres were prepared by o/w solvent evaporation... more Abstract Flurbiprofen loaded PCL/PVP blend micro-spheres were prepared by o/w solvent evaporation method using various concentrations of gelatin as emulsifying agent. Microsphere recovery decreased with a decrease in the concentration of the emulsifier in the dispersion. Encapsulation ...

Multiferroic materials are of particular interest due to the co-existence of ferromagnetic and fe... more Multiferroic materials are of particular interest due to the co-existence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO3, BFO) is the only material that shows both ferroelectric and antiferromagnetic properties at room temperature. However, synthesis of phase pure BFO is difficult due to volatile nature of Bi2O3. In this work, bismuth iron oxide nanoparticles are synthesized using sol-gel technique. With change in synthesis conditions a transition from amorphous nature to crystalline behavior is observed. The crystalline nature of nanoparticles strongly affects the dielectric and magnetic properties. High dielectric constant of ~300 (frequency =1kHz) is obtained due to presence of less conducting grain boundaries. Ferromagnetic behavior, instead of antiferromagnetic bismuth iron oxide, arises due to suppression of spiral spin structure of bismuth iron oxide.

Multiferroic materials like Bismuth Iron Oxide (BiFeO3), YMnO3, BiMnO3, TbMnO3 has attracted worl... more Multiferroic materials like Bismuth Iron Oxide (BiFeO3), YMnO3, BiMnO3, TbMnO3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these materials BiFeO3 is a promising candidate as it exhibits room temperature antiferromagnetic and ferroelectric properties. However, BiFeO3 suffers from some drawbacks including weak magnetic behavior, inhomogeneity in spin structure and large leakage current. In order to overcome these problems we here report Lanthanum (La) doped Bi1-xLaxFeO3 (where, x=0.0-0.5) thin films prepared by sol-gel method. The effect of La substitution on structural and dielectric properties has been investigated. The films show pure phase rhombohedrally distorted perovskite structure of BiFeO3. XRD peak shifts to high angles due to slight difference in ionic radii of La (1.16Å) and Bi (1.17Å). The dielectric constant and tangent loss decreases as frequency increases and becomes c...

ZnO semiconductor is a potential candidate for the information processing, energy storage, commun... more ZnO semiconductor is a potential candidate for the information processing, energy storage, communication and optoelectronic devices. Various physical properties of the ZnO have been demonstrated both experimentally and theoretically. We reported the different characteristics of undoped and Indium doped ZnO using first principle calculations under the framework of density functional theory. Both wurtzite and zincblende phases of the ZnO are examined using local density approximations (LDA) and generalized gradient approximation (GGA) with different exchange correlation potential within DFT for band structure calculations. Results reveal that the pure ZnO is a direct band gap semiconductor which can be employed for wide range of optoelectronics devices. The accuracy of the results are also checked with reported experimental data which are in consistent. We investigated Indium metal doped ZnO, in order to explore the influence of the doping on structural and optical properties. The ban...

Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique ... more Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique and novel properties. Amsterdam density functional (ADF) software is used for the first time in order to theoretically investigate the structural properties of cobalt doped iron oxide at 0K. TZ2P is used as basis set. Using GGA geometry optimization was achieved to observe structural properties. Inverse spinel cubic structure with lattice parameter of 8.39 Å is confirmed after geometry optimization by using GGA. 2X1X1 super cell of cobalt doped iron oxide is formed and GGA:PBE method is used to obtain total density of states (DOS) along with partial DOS of iron, cobalt and oxygen, respectively. Increase in band gap energy at 0K is observed after applying Hubbard potential (U=3 and 4 eV) for cobalt and iron, respectively.

Magnetic nanostructures including nanowires (NWs) and nanotubes (NTs) have attracted considerable... more Magnetic nanostructures including nanowires (NWs) and nanotubes (NTs) have attracted considerable scientific interest during the last decade because of their potential applications in sensors, microwave absorption, biological separation and high density recording media. A comprehensive study of magnetization properties for MCoO (M=Ni, Fe) core-shell nanowires has been carried out. Ferromagnetic nanowires arrays layered with Cobalt oxide shell are fabricated by sol gel route followed by DC electrodeposition into AAO templates. Scanning electron microscope was used to analyse the morphology of fabricated nanowires. Structural analyses reveal the formation of highly ordered, dense and uniformly distributed core-shell nanowires. Magnetic hysteresis loops indicated that for core-shell nanowires easy axis of magnetization lie parallel to the wire long axis.

Tin oxide (SnO2) doped and un-doped indium oxide (In2O3) nanoparticles are synthesized by the sol... more Tin oxide (SnO2) doped and un-doped indium oxide (In2O3) nanoparticles are synthesized by the sol-gel method while anhydrous indium chloride (InCl3) and anhydrous tin chloride (SnCl4) are used as the source of indium and tin respectively, for the formation of indium tin oxide (ITO) thin films. Ethanol is used as solvent to get homogenous solution. Acetic acid (CH3COOH) was also added drop wise in this solution. Thin films of doped and un-doped In2O3 are deposited on glass substrate at room temperature and annealed at different temperatures ranging from 50°C to 500°C. The XRD patterns of thin films indicates the main peak of (12 4 ) plane and showed a higher degree of crystallinity in annealed thin films. Average crystallite size of 10.9 nm to 29.3 nm is observed in all the deposited thin films. The optical transmittance spectra of SnO2 doped In2O3 thin films showed the fundamental absorption edge with increment in annealing temperature. The band gap of thin films is observed to be f...

Gold nanoparticles, owing to their fascinating optical properties, are considered very attractive... more Gold nanoparticles, owing to their fascinating optical properties, are considered very attractive for detecting devices. Size, shape as well as surrounding environment may affect the sensing behavior of nanomaterial and thus the study of such factors is of great importance. We investigatedthe gas sensing performance of colloidal gold nanoparticles of different sizes in carbon dioxide gaseous environment by measuring the optical behavior with and without gas. The citrate reduction method was adopted to synthesize gold nanoparticles; scanning electron microscopy was used for morphological studies while optical properties were determined by spectroscopic ellipsometery. We observed a size dependent decrease in the transmission spectra of colloidal gold nanoparticles in the presence gaseous environment.

Journal of Alloys and Compounds, 2016

In present work, a series of Ba 2 Co 2Àx Mn x Fe 12 O 22 nanoparticles (x ¼ 0.0, 0.1, 0.3, 0.5, 0... more In present work, a series of Ba 2 Co 2Àx Mn x Fe 12 O 22 nanoparticles (x ¼ 0.0, 0.1, 0.3, 0.5, 0.7, and 0.9) has been synthesized by hydrothermal method. Effect of Mn substitution on structural, microstructure and magnetic properties has been investigated in detail. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analyses confirmed the formation of Y-type hexagonal ferrite structure. Morphology and chemical composition studies performed by Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy conformed that with increasing Mn concentration grain size increases from few nanometers to micrometer range. Furthermore, magnetic analyses revealed that with increasing Mn concentration at octahedral and tetrahedral sites the coercivity and squareness were found to increase from 455Oe to 2550Oe, and 0.26 to 0.56, respectively. Theoretical approach was also used to calculate saturation magnetization of synthesized samples. The synthesized nanoparticles with enhanced magnetic characteristics are ideal candidate for their use in perpendicular magnetic recording and high frequency applications.

IEEE Transactions on Magnetics, 2014

ABSTRACT Doping effects of acidic (pH4) and basic (pH10) Fe3O4 on the magnetic properties of ZrO2... more ABSTRACT Doping effects of acidic (pH4) and basic (pH10) Fe3O4 on the magnetic properties of ZrO2 have been reported in this paper. Fe3O4 doped zirconia (FZ) sol is synthesized by varying Fe3O4 concentrations in the range of 2–10 wt% using sol-gel route. FZ sols are spin coated onto glass substrates and then vacuum annealed at 300 °C for 60 min in the presence of 500 Oe magnetic field. X-ray diffraction results show amorphous behavior at 2 wt% doping in both acidic and basic cases. Mixed monoclinic-tetragonal behavior is observed in acidic films with 6–10 wt% doping concentration. However, tetragonal phase is observed in basic films with 8–10 wt% doping. Soft ferromagnetic behavior is observed in both the acidic and basic doped zirconia. Saturation magnetization (M (_{mathrm {s}}) ) of (sim 33) emu/g is observed in acidic FZ samples whereas, variation in M (_{mathrm {s}}) (1–36 emu/g) is observed in basic FZ samples. Iron oxide stabilized ZrO2, with soft ferromagnetic behavior, can be employed for coatings on teeth as well as for diagnosis and therapy of oral cancer.

IEEE Transactions on Magnetics, 2014

ABSTRACT The safe, targeted and effective release of drugs for therapeutics from nanostructured f... more ABSTRACT The safe, targeted and effective release of drugs for therapeutics from nanostructured functional materials, particularly nanoparticles (NPs), has attracted much attention due to the ability to diagnose and cure of cancer and other ailments. The potential of magnetic NPs, that stems from intrinsic properties of their magnetic cores combined with their drug, can be exploited for clinical applications. Two main magnetic requirements for bionanotechnology—a high saturation magnetic moment and a near-zero remanence—occur in superparamagnetic materials. Here, we report synthesis of magnetite NPs by modified coprecipitation method. The effect of pH on the shape and size of NPs has also been reported in this paper. For superparamagnetic nature, the size of the NPs has great significance and should be compatible with the living cell. Ferric and ferrous chlorides are used as precursors and the amount of NaOH was varied to control the size and shape of the nanoparticles. X-ray diffraction patterns show the formation of magnetites. Scanning electron microscopy reveals that the prepared nanoparticles have size compatible with the diseased cell. M-H curves show the superparamagnetic nature of the nanoparticles, hence these NPs are well suited for the magnetic resonance imaging as the contrast agents, for cell tagging, magnetic separation, and hyperthermia treatments.

IEEE Transactions on Magnetics, 2014

Iron oxide nanoparticles have attracted wide attention due to applications in biomedical sciences... more Iron oxide nanoparticles have attracted wide attention due to applications in biomedical sciences like MRI contrast agents, drug delivery, etc. In this work iron oxide (Fe O) nanoparticles (NPs) with very narrow size distribution are obtained by using sol-gel method. FeCl H O, ethanol and NaOH are used as precursor, solvent and gelation agent, respectively. Controlled addition of oleic acid helps in the reduction of uncoated particle/crystallite size down to 10 nm and in achieving superparamagnetic behavior of iron oxide NPs. Coating of magnetic NPs is quite important to make them biocompatible and to prevent the aggregation and degradation of metal oxide. Silica, being nontoxic, biocompatible and containing hydroxyl groups attached to its surface, is used for coating purposes. Silica provides hydrophilic properties and thus helps in the attachment of specific drugs and biomolecules. For comparative purposes NPs are also coated by carbon which provides a barrier to oxidation of NPs. XRD studies show the formation of crystalline core shell nanoparticles with decrease in peak intensities as compared to uncoated nanoparticles due to the shielding effect of an amorphous silica shell. Wall thickness of the shell is varied by changing the concentration of ammonia and water to ethanol ratio in silica coated nanoparticles whereas concentration of glucose solution in carbon coated NPs. Coated NPs from 20-50 nm are observed by scanning electron microscopy by changing the concentration of coating solution. Saturation magnetization decreases as the particle size increases due to increased thickness of silica shell. Core-shell nanoparticles show high thermal stability as compared to uncoated nanoparticles.

Applied Physics A, 2008

Hair loss can have significant effects on patients' quality of life, and a prompt diagnosis of th... more Hair loss can have significant effects on patients' quality of life, and a prompt diagnosis of the different types of alopecias and an early intervention is needed. This review highlights the main dermoscopic findings in the different types of alopecia, as androgenetic alopecia, alopecia areata, trichotillomania, lichen planopilaris and discoid lupus erythematosus of the scalp. We believe that this important tool has demonstrated to help dermatologists in finding the right site for the biopsy, or furthermore avoiding unnecessary biopsies. Through photograph assessment, follow up of patients is also best appreciated at each visit.

IEEE Transactions on Magnetics, 2014

ABSTRACT Mn/Fe co-doped ZnO thin films are prepared by simple sol–gel and spin coating method. Fi... more ABSTRACT Mn/Fe co-doped ZnO thin films are prepared by simple sol–gel and spin coating method. Five different sols with the change in concentration (1–5 wt%) of both Mn and Fe are synthesized. Molar ratio of Mn and Fe is kept constant, i.e., 1:1. Sols are spun onto glass and copper substrates by spin coating method followed by the post magnetic field annealing at 300 °C for 1 h. Effect of Mn and Fe codoping on ferromagnetic properties of ZnO is reported in this paper. Structural and magnetic properties of as prepared and annealed samples are investigated by X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). Scanning electron microscope is used to study the surface morphology of co-doped films. XRD results show incorporation of Mn and Fe in the host lattice upto a dopant concentration of 4 wt%. However, small crystallites of Mn and Fe2O3 are observed by increasing the dopant concentration to 5 wt%. VSM results indicate room temperature ferromagnetism in all samples without the presence of any secondary phases. Low value of shape anisotropy is observed in the case of Mn doped ZnO. However, no shape anisotropy is observed in the case of co-doped thin films. Moreover, Mn/Fe co-doped thin films show magnetic hysteresis equivalent to that of multilayered structure, indicating that such complex structures used in spintronic devices can be replaced by a single ZnO layer with codoping of Mn and Fe.

Impact ionization in fully depleted (FD) Silicon On Insulator (SOI) n-Channel MOSFET is investiga... more Impact ionization in fully depleted (FD) Silicon On Insulator (SOI) n-Channel MOSFET is investigated as a function of the doping concentration. We have found that impact ionization increases with the decrease in the doping concentration and vice versa. Simulation results obtained from Sentaurus TCAD with the higher doping concentration can control the threshold voltage (V th). Furthermore we have examined the effect of doping concentration on the transconductance (g m) and have observed that transconductance is inversely proportional of the doping concentration.

2015 IEEE Magnetics Conference (INTERMAG), 2015

Magnetic nanoparticles have attracted broad attention due to their potential biomedical applicati... more Magnetic nanoparticles have attracted broad attention due to their potential biomedical applications, such as contrast agents for magnetic resonance imaging (MRI), heating mediators for cancer therapy (hyperthermia), and magnetic labels for biosensing. For nanoparticles to be utilized for biomedical applications these nanoparticles must acquire superparamagnetic behavior with relatively high value of saturation magnetization [1-3]. However, the main challenge in the use of these nanoparticles is the functionalization of particle surface [4-5]. Magnetite (Fe3O4) nanoparticles, with diameter of ~20nm, are synthesized using sol-gel method. Uncoated Fe3O4 nanoparticles show superparamagnetic behavior as shown in Fig. 1. For making these nanoparticles useful in MRI contrast agent, nanoparticles were coated with citric acid. Citric acid (C6H8O7) is a short chained molecule containing three carboxylate groups [6-8]. Citric acid gets adsorbed on the surface of superparamagnetic iron oxide n...

JOURNAL OF FACULTY OF ENGINEERING & TECHNOLOGY, 2015

Wear and friction behaviour of yttria stabilised zirconia coatings are very sensitive to the stru... more Wear and friction behaviour of yttria stabilised zirconia coatings are very sensitive to the structure of the material and test parameters such as temperature, applied load, sliding speed, and environment. The present study describes the friction, and sliding wear behaviours of plasma sprayed yttria stabilized zirconia coating (ZrO 2 -8wt.%Y 2 O 3 (YSZ) deposited on a stainless steel substrate with NiAl bond coat. Tribological properties of the coating were assessed under lubrication condition at loads of 4N and 8N. The frictional behaviour of coating was assessed at a constant temperature of 50°C, while wear characteristics of the coating were investigated at 50°C and 100°C. The experimental results of this study showed a slight decrease in frictional coefficient with increasing load. However, the coating wear rate was slightly increased with increasing load and temperature. The coating wear mainly involved materials transferred from the counter body and pulling-out from the coatin...

In-Plane Semiconductor Lasers V, 2001

Journal of Sol-Gel Science and Technology, 2009

Journal of Alloys and Compounds, 2016

IEEE Transactions on Magnetics, 2014

Applied Physics A, 2008

IEEE Transactions on Magnetics, 2014

2015 IEEE Magnetics Conference (INTERMAG), 2015

JOURNAL OF FACULTY OF ENGINEERING & TECHNOLOGY, 2015

A Sol-gel dip coating route has been employed to synthesize cobalt oxide thin films on glass subs... more A Sol-gel dip coating route has been employed to synthesize cobalt oxide thin films on glass substrates. The obtained films are characterized by X-ray diffraction (XRD), UV-VIS spectrophotometer, vibrating sample magnetometer (VSM), Scanning Electron Microscope and Fourier Transform Infra Red (FTIR) spectroscopy. The films are identified as Co 3 O 4 by FTIR. XRD further confirmed Co 3 O 4 phase. Upon increasing withdrawal speed of substrate, the transmission and band gap decreases due to increase in film thickness. Thin films show room temperature ferromagnetism and magnetic properties enhance by increasing thickness of thin films. SEM shows porous surface of films.

The mesoporous SiO 2-TiO 2 nano-composite was obtained via the sol – gel method. The presence of ... more The mesoporous SiO 2-TiO 2 nano-composite was obtained via the sol – gel method. The presence of surfactant additive CTAB as structure-directing agent leads to the textural modification of composite network after heat treatment at 150°C for 2 hrs. The both samples before and after heat treatment were characterized by BET method, nitrogen adsorption–desorption methods and UV-Vis Spectroscopy. N2 adsorption isotherms of the annealed sample explaining the high surface area value of silica-titania nano-composite is 401m 2 /g with a pore size of 3.3 nm and pore volume of 0.33 cm 3 /g. The influence of surfactant CTAB on the pore structure and surface area of sol-gel based silica-titania nano-composite for pH sensing applications were also investigated. Furthermore, the EDX analysis substantiated the stiociomatric formation of encapsulated silica-titania nano-composites.

In the present work, TiO 2 nanoparticles have been prepared by a sol-gel auto-combustion method u... more In the present work, TiO 2 nanoparticles have been prepared by a sol-gel auto-combustion method using titanium tetrachloride as a precursor material, with an aim to get the anatase phase for the photocatalytic applications. Six samples were prepared using three different fuel materials i.e., citric acid, urea and glycine, respectively. First three samples were obtained without thermal treatment and last three samples were obtained by sintering the first three samples at 350 °C, using the same three fuel materials. X-ray diffraction revealed that thermally sintered samples were consisting of pure anatase phase. The dielectric parameters were found to decrease with increase in frequency depicting characteristic oxide behaviour. It has been observed that the sample prepared using urea as a fuel material and subsequently sintered at 350 °C revealed better structural and electrical behaviour characteristic of pure anatase phase of TiO 2. The morphology was examined by scanning electron microscope and growth of particles was found to be much uniform for the sample obtained by using glycine as fuel material.

Multiferroic materials like Bismuth Iron Oxide (BiFeO 3), YMnO 3 , BiMnO 3 , TbMnO 3 has attracte... more Multiferroic materials like Bismuth Iron Oxide (BiFeO 3), YMnO 3 , BiMnO 3 , TbMnO 3 has attracted worldwide attraction due their applications in data storage devices, spintronic devices, sensors and multiple stage memories. Among these materials BiFeO 3 is a promising candidate as it exhibits room temperature antiferromagnetic and ferroelectric properties. However, BiFeO 3 suffers from some drawbacks including weak magnetic behavior, inhomogeneity in spin structure and large leakage current. In order to overcome these problems we here report Lanthanum (La) doped Bi 1-x La x FeO 3 (where, x=0.0-0.5) thin films prepared by sol-gel method. The effect of La substitution on structural and dielectric properties has been investigated. The films show pure phase rhombohedrally distorted perovskite structure of BiFeO 3. XRD peak shifts to high angles due to slight difference in ionic radii of La 3+ (1.16Å) and Bi 3+ (1.17Å). The dielectric constant and tangent loss decreases as frequency increases and becomes constant at high frequencies showing normal dispersion behavior for all concentrations (i.e. x=0.0-0.5). The dispersion in dielectric constant occurs due to the time required by the carriers to get align in the direction of field. At high frequencies the field reversal is so high that the carriers do not get enough time to get aligned in the direction of field thus resulting in low dielectric constant at high frequency. The dielectric constant is strongly affected by changes in grain size. Decrease in grain size leads to increase in number of grain boundaries hindering the hopping process between the different states and grains thus resulting in accumulation of cations at the grain boundaries thus affecting the dielectric constant.

During the past few years, multiferroic materials i.e. materials exhibiting ferroelectricity and ... more During the past few years, multiferroic materials i.e. materials exhibiting ferroelectricity and ferromagnetism have acquired worldwide attraction due to its wide range of applications in devices as small as sensors to devices as large as transformers. Among various multiferroic materials, bismuth iron oxide is a promising candidate. However, there are some drawbacks associated with phase pure BiFeO 3 including volatility of Bi 2 O 3 , large leakage current and antiferromagnetic/ weak ferromagnetic behavior. In this work bismuth iron oxide nanoparticles (NPs) are synthesized using sol-gel technique. NPs are calcined at 100˚C, 200˚C and 300˚C. Bismuth iron oxide NPs are characterized using x-ray diffractometer, vibrating sample magnetometer and impedance analyzer. NPs show amorphous behavior under as-prepared conditions. Dielectric constant increases from 49 to 74 (at frequency = 1MHz) and tangent loss decreases from 0.2 to 0.012 with increase in calcination temperature from 100-300˚C. Ferromagnetic behavior instead of antiferromagnetic nature of bulk bismuth iron oxide arises due to suppression of helical spin structure. The suppression of spin structure leads to ferromagnetic behavior with saturation magnetization of 7.125×10-4 emu, 1.28×10-3 emu and 1.59×10-3 emu at 100˚C, 200˚C and 300˚C.

In order to obtain a bioactive material; with high mechanical strength, high fracture toughness a... more In order to obtain a bioactive material; with high mechanical strength, high fracture toughness and aesthetic properties needs to be fabricated. Such properties can be obtained in ceramics. Zirconia ceramics have gained favor as restorative materials because of their excellent mechanical properties; they have high strength and toughness, good biocompatibility, and relatively good aesthetic properties. But the problem with zirconia is inertness with the body fluid and it resists the formation of bonds with bones and tissues. This problem can be minimized by some biocompatible additives. This explorative study was performed to examine a possible impact of polymer on ZrO 2 nanoparticles (NPs). Along with effect of reaction temperature (50, 100 and 150°C) has been investigated on structural and mechanical properties of polymer additive zirconia. XRD results illustrate the partially stabilized zirconia (PSZ) however, monoclinic content decreases with increase in reaction temperature. A decrease in crystallite size has observed due to structural changes. A decrease in particle size has found at higher reaction temperatures. The mechanical properties of the samples were characterized by Micro Vickers Hardness tester and hardness of the samples is in the range of 590HV to 1000HV.

In the present study sol–gel method has been employed using polymers additives to deposit zirconi... more In the present study sol–gel method has been employed using polymers additives to deposit zirconia thin films. Effect of reaction temperature (50, 100 and 150°C) have been investigated on structural and mechanical properties of zirconia thin films. Addition of polymers has prominent effect on structural and mechanical properties of zirconia. Phase analysis was executed by X-Ray diffractrometer (XRD). Formation of tetragonal zirconia (t-ZrO 2) along with monoclinic content has been observed at relatively higher reaction temperatures (100 and 150°C). A sharp decrease in crystallite has observed at reaction temperature 100°C. Higher reaction temperatures cause volume shrinkage due to removal of hydroxyl (OH) ions since OH ions are responsible for monoclinic content. Removal of OH ions at relatively higher reaction temperatures leads to presence of tetragonal zirconia at room temperature. Hardness of the polymer additive zirconia has obtained up to 850HV confirmed by Micro Vickers hardness indenter. These as deposited thin films with presence of tetragonal content can be successfully employed for teeth coatings.

We here report the preparation and characterization of cobalt doped iron oxide nanoparticles usin... more We here report the preparation and characterization of cobalt doped iron oxide nanoparticles using sol-gel method. The dopant concentration is varied as 2%, 4%, 6%, 8% and 10%. The position of diffraction peaks shifts to slightly higher angles due to smaller ionic radii of cobalt as compared to that of iron. No peaks corresponding to cobalt or cobalt oxide are observed indicating that dopant has been successfully incorporated in the host lattice. Cobalt with electronic configuration of [Ar]3d 7 4s 2 has one more electron than iron. Cobalt atom donates one d and two s electrons to oxygen that results in remaining six electrons on cobalt. When Co is substituted for Fe with spin down electron the spin down d band gets completely filled with remaining one d-electron residing in spin up band. This results in increase in net magnetization in cobalt doped iron oxide nanoparticles as compared to undoped iron oxide nanoparticles.

Amongst various phases of iron oxide, hematite (α-Fe 2 O 3) has attracted world attraction due wi... more Amongst various phases of iron oxide, hematite (α-Fe 2 O 3) has attracted world attraction due wide range of technological and industrial applications including spintronic and data storage devices. However hematite exhibits weak ferromagnetic behavior at room temperature. For enhancing the magnetic properties of hematite nanoparticles we here report structural and magnetic properties of Cr doped Fe 2 O 3 nanoparticles prepared using sol-gel method. The dopant concentration is varied as 2%, 4%, 6%, 8% and 10%. The nanoparticles are characterized using Bruker D8 Advance X-ray Diffractometer (XRD) and Lakeshore's 7407 Vibrating Sample Magnetometer (VSM). Presence of (012), (104), (110), (113), (024), (116), (214) and (300) planes in XRD indicate the formation of Fe 2 O 3 phase. XRD results indicate that incorporation of chromium causes contraction in unit cell that shifts the peak positions to higher diffraction angles. Undoped iron oxide nanoparticles show weak ferromagnetic behavior because of the presence of uncompensated magnetic moments between two sublattice that give rise to canting of spin structure. Incorporation of chromium in the host hematite lattice leads to appearance of localized magnetic moments in hematite nanoparticles thus leading to increase in magnetic properties. At high dopant concentration, Cr atoms can go to the interstitial positions thus, possibility of having free Cr atoms at high dopant concentration lead to the distortion of magnetic behavior.

The un-doped and Fe-doped ZnS nanocrystalline thin films were deposited on glass substrates by ch... more The un-doped and Fe-doped ZnS nanocrystalline thin films were deposited on glass substrates by chemical bath deposition (CBD). Iron chloride, zinc chloride and thioacetamide were used as precursors and de-ionized water was used as solvent. The synthesis and deposition of thin films was carried out without using any surfactant/capping agent. The powder X-ray diffraction patterns reveal the formation of cubic zinc blende phase of ZnS in all cases. The incorporation of iron in ZnS lattice was confirmed by the change in lattice parameters accordingly with doping concentration and absence of traces of secondary phases or Fe clusters. The M-H curves indicate that doped ZnS thin films exhibit room temperature ferromagnetism. The magnetization properties as a function of field angle and doping concentration were studied in detail. The density functional calculations were performed using Full Potential Linearized Augmented Plane Wave (FPLAPW) as is employed in elk-code. The strong p-d hybridization observed between sulphur and iron result in ferromagnetic stable state and half metallicity in these materials. The half metallic iron doped ZnS thin films can have applications in future spintronic devices. 1. INTRODUCTION The research interest is focused during the last decade on the experimental and theoretical study of DMSs offering T c above room temperature. The T c of II-VI semiconductors (ZnS and CdS) based DMS is found to be very close to room temperature and can be adjusted by the different synthesis parameters especially the dopant concentration. The Mn doped InAs was reported as DMS with T c above room temperature (Holub 2004). The ZnS being an important II–VI compound semiconductor with direct wide band gap may be expected to be ferromagnetic at room temperature. The transition metal doped ZnS are found to be half metallic when doped with Cr, Fe, and Ni while maintain its semiconducting nature when doped with Mn and Co (Stern 2004 and McNorton 2008). Tablero (2006) found that ZnS doped with Cr has a partially filled intermediate band for both FM and AFM spin alignments.

Maghemite (γ-Fe 2 O 3) is one of the promising candidates for its use in biomedical and in optoel... more Maghemite (γ-Fe 2 O 3) is one of the promising candidates for its use in biomedical and in optoelectronics. Density functional theory (DFT) with generalized gradient approximation (GGA:PBE) is used in order to study structural and optical properties of iron oxide. By using BAND tool with basis set of TZ2P, geometry optimization is achieved. Cubic spinel structure is confirmed after geometry optimization with bond length of 3.55 Å between iron and oxygen in γ-Fe 2 O 3. Amount of Hirshfeld charge is observed to be 18.02, 28.39 for Fe(1) and Fe(2), respectively instead of 26.00. While for all three oxygen atoms its value increases from 8.00 to 9.85. Indirect band gap of γ-Fe 2 O 3 is observed with value of 0.68 eV without applying Hubbard potential U. After applying Hubbard potential U=3 band gap of 2.1eV is achieved which is in agreement to the experimental value of 2.0 eV (Zhu et al. 2013). Total density of states along with partial density of states for iron and oxygen is also studied. It is important to mansion it here that it is the first time to use Amsterdam Density Functional software to investigate properties of maghemite and all these calculations were carried out at 0K.

Cubic FeO has been studied by using density functional theory. Generalized gradient approximation... more Cubic FeO has been studied by using density functional theory. Generalized gradient approximation (GGA:PBE) and local density approximation (LDA) is used in order to study optical and structural properties of iron oxide. By using BAND tool with basis set of TZ2P geometry optimization is achieved and fcc structure is observed. It is important to mention it here that all the calculations were taken at 0K by using Amsterdam density functional software for the first time to investigate structural and electronic properties of FeO (wüstite). Band gap of 0.615 eV and 0.75 eV is observed by GGA and LDA. While, 2.2 eV and 1.89 eV is obtained by GGA+U and LDA+U respectively. Constant value of Hubbard potential (U) is used for both approximations i.e. 6.4 eV. Total DOS and partial density of states for iron and oxygen is also studied for both approximations. Analysis of the density of states confirms the strong hybridization between Fe 3d and O 2p states in FeO. The bond length between iron and oxygen is examined and found to be 3.74Å with total bonding energy of 15.99 eV.

The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of ... more The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. Nanoparticles (NPs) have attracted considerable attention owing to their unique properties and ease of production from variety of materials. Zirconia with enhanced properties can be achieved by doping with biocompatible material. The present study devised sol gel method for preparation of Fe 3 O 4 doped ZrO 2 nanoparticles (NPs). Zirconia sol is doped with pre-synthesized Fe 3 O 4 NPs. Structural characterizations have shown a mixture of monoclinic and tetragonal zirconia. An increase in crystallite size has observed with dopant concentration. Lattice contraction was observed for the Fe 3 O 4-doped zirconia samples. This lattice contraction results in volumetric change which leads to formation of tetragonal phase. Relative higher density (~6g/cm 3) has been observed which is perquisite for implantations and coatings. Magnetic properties reveal the mix paramagnetic and ferromagnetic behavior with low value of coercivity and magnetization.

Multiferroic materials are of particular interest due to the coexistence of ferromagnetic and fer... more Multiferroic materials are of particular interest due to the coexistence of ferromagnetic and ferroelectric properties. Among various multiferroics, bismuth iron oxide (BiFeO 3 , BFO) is the only material that shows both ferroelectric and antiferromagnetic properties at room temperature. However, synthesis of phase pure BFO is difficult due to volatile nature of Bi 2 O 3. In this work, bismuth iron oxide nanoparticles are synthesized using sol-gel technique. With change in synthesis conditions a transition from amorphous nature to crystalline behavior is observed. The crystalline nature of nanoparticles strongly affects the dielectric and magnetic properties. High dielectric constant of ~300 (frequency =1kHz) is obtained due to presence of less conducting grain boundaries. Ferromagnetic behavior, instead of antiferromagnetic bismuth iron oxide, arises due to suppression of spiral spin structure of bismuth iron oxide.

Iron oxides are material of interest because of their use in spintronic devices including Magneti... more Iron oxides are material of interest because of their use in spintronic devices including Magnetic Tunnel Junctions (MTJ) and Random Access Memories (RAM). Among the various phases of iron oxide, Fe 2 O 3 is the most stable form which shows antiferromagnetic or weak ferromagnetic behavior at room temperature. In order to enhance magnetic properties of Fe 2 O 3 , we here report the structural and magnetic properties of aluminum (Al) doped Fe 2 O 3 thin films prepared using sol-gel method. Effect of aluminum doping on Fe 2 O 3 thin films have been given very little consideration in the past particularly the reports on magnetic properties are limited. The presence of (012), (110), (006), (202), (024), (214) and (217) planes indicate the formation of pure hematite phase. No peaks corresponding to aluminum or aluminum oxide are observed. The undoped hematite thin films show ferromagnetic behavior as opposed to antiferromagnetic nature of bulk hematite. In case of hematite, spins in the adjacent planes are ferromagnetically coupled whereas, antiferromagnetic coupling arises with the spins of the adjacent planes. Spin orbit coupling between the two adjacent planes give rise to uncompensated spins of Fe 3+ cations. Remarkable increase in magnetic moment is observed with the increase in dopant concentration.

Conducting nanocomposites of polyaniline/maghemite (PANI/ᵞ-Fe 2 O 3) have successfully prepared w... more Conducting nanocomposites of polyaniline/maghemite (PANI/ᵞ-Fe 2 O 3) have successfully prepared with different weight percentages of ᵞ-Fe 2 O 3 (0-0.5 wt. %) by adopting chemical oxidation route at 5ºC. These nanocomposites were characterized for their structure, morphology and dc electrical conductivity by fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and standard two point probe method respectively. It can be clearly seen that dispersion of ᵞ-Fe 2 O 3 has imparted good structural and conducting properties in PANI matrix. The percolation threshold for dc electrical conductivity was found at 0.3% filling of maghemite contents in PANI chains.