M. Esthaku Peter; Getahun Leliso; Seblewongel Getachew; Betelhem Alemu; Tirngo Abay; Eleni Binalfeus
Abstract
A single crystal of D-Tartaric acid, a stereoisomer of tartaric acid, has been grown by a slow solvent evaporation technique. Good crystals to be used for optical testing were harvested after multiple recrystallizations, whose maximum size is 30x20x4mm 3 . In view of finding second harmonic generation ...
Read More
A single crystal of D-Tartaric acid, a stereoisomer of tartaric acid, has been grown by a slow solvent evaporation technique. Good crystals to be used for optical testing were harvested after multiple recrystallizations, whose maximum size is 30x20x4mm 3 . In view of finding second harmonic generation efficiency and properties supporting for a nonlinear optical device, the grown crystals were subjected to various characterizations. Firstly, the compound was confirmed by single crystal and powder X-ray diffraction analysis and thereafter further studies were undertaken. Various possible functional groups available in the grown crystalline compound were identified using Fourier transform infrared analysis and reported. The second harmonic generation, a nonlinear optical property of a crystal, was studied and compared with standard KDP crystal. The percentage of linear optical transmittance in the ultraviolet, visible and infrared radiation of wavelength ranging from 200 to 1100 nm was studied and explained in detail. Thermal studies such as Thermogravimetric and Differential thermal analysis were carried out to find the thermal stability of the crystalline material. Vicker’s microhardness testing was made on the as-grown crystalline surface to find the surface hardness, yield strength and other related mechanical properties of the crystal. Copyright © VBRI Press.
Kumara Raja Kandula; Sai Santosh Kumar Raavi; Saket Asthana
Abstract
Nd 3+ -substituted lead free 0.94(Na0.5Bi0.5-XNdXTiO3)-0.06BaTiO3 (x=0, 0.01) ceramics were synthesized by using conventional solid state route. The XRD studies revealed the phase purity and existence of the monoclinic (Cc), cubic (Pm3m) along with the minor tetragonal phases confirmed with help of structural ...
Read More
Nd 3+ -substituted lead free 0.94(Na0.5Bi0.5-XNdXTiO3)-0.06BaTiO3 (x=0, 0.01) ceramics were synthesized by using conventional solid state route. The XRD studies revealed the phase purity and existence of the monoclinic (Cc), cubic (Pm3m) along with the minor tetragonal phases confirmed with help of structural refinement. The electrical poling field induces the structural modification to rhombhohedral (R3c), cubic (Pm3m) along with the minor tetragonal phase (P4mm). The dielectric measurements revealed the relaxor behavior. The coercive field drops remarkable and there is slight improvement in the polarization with the substitution of Nd as compared to the pure 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3. The luminescence occurred from the optically active element Nd 3+ under the influence of the average crystal symmetry of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3. The luminescence quenching observed without any shift in position upon the poling supports the observation of higher symmetric structure.
Akhilesh Pandey; Shankar Dutta; Anand Kumar; R. Raman; Ashok K. Kapoor; R Muralidhran
Abstract
Molybdenum-di-sulfide (MoS2) is being considered as an alternative 2-D material to graphene. Deposition of ultrathin MoS2 layer from bulk MoS2 sample is an important criterion in determining the viability of its application. This paper discusses about growth and characterization of bulk MoS2 pellet ...
Read More
Molybdenum-di-sulfide (MoS2) is being considered as an alternative 2-D material to graphene. Deposition of ultrathin MoS2 layer from bulk MoS2 sample is an important criterion in determining the viability of its application. This paper discusses about growth and characterization of bulk MoS2 pellet from MoS2 powder and exfoliation of MoS2 layer from it. The MoS2 pellets were sintered at different temperatures (500 - 850 ° in nitrogen atmosphere. The sintered samples were found to be polycrystalline in nature with hexagonal flakes of 100 nm – 1.0 µm sizes. In addition to MoS2 phase, surface of the bulk samples also has also some MoO3 phase content, which was found to decrease with the increase in sintering temperature, confirmed by XRD. The optical absorption study showed MoS2 absorptions around 1.82 eV, 2.01 eV due to spin orbit and direct band to band absorption from ?k-k valley. The sintered MoS2 samples were found to have characteristic Raman peaks of A1g and E2g with a separation of 26.5 cm -1 . Ultrathin MoS2 layers, exfoliated from the sintered sample, showed the reduced separation between Raman peaks A1g and E2g of 24.5 cm -1 few layer MoS2.
Sudip. K. Sinha
Abstract
We report the thermal annealing effect of ZnO-SnO2 composite thin films deposited by pulsed laser deposition on its structural, electrical, and optical properties. The results present a consistent portrayal of the evolution of ZnO-SnO2 composite oxide films phase formation in post-annealed condition ...
Read More
We report the thermal annealing effect of ZnO-SnO2 composite thin films deposited by pulsed laser deposition on its structural, electrical, and optical properties. The results present a consistent portrayal of the evolution of ZnO-SnO2 composite oxide films phase formation in post-annealed condition and its subsequent effect on various physical properties. X-ray diffraction confirms that the films transform from nearly amorphous to fully crystalline state on thermal annealing at 600 °C. X-ray photoelectron spectroscopy reveals a small shift in Sn-3d peak towards lower energy and O-1s and Zn-2p < /em> peaks towards higher binding energy with increasing ZnO concentration and confirms the formation of combined oxides of ZnO and SnO2. The average optical transmission is greater than 80 % in the visible region of the annealed ZnO-SnO2 composite films. The lowest electrical resistivity of 9.8 × 10 -4 Ωcm has been obtained in the film containing 25 wt % ZnO. Our results suggest that annealed ZnO-SnO2 composite films with improved electrical and optical properties could find potential use in thin film solar cells or touch pad control panels.
Shweta Thakur; Seema Sharma;Ashutosh Tiwari; Radheshyam Rai
Abstract
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have ...
Read More
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have pure pervoskite phase with tetragonal structure at room temperature and have maximum value of dielectric constant at x = 0.9. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz–1MHz) and temperatures (30 – 500 o C) showed that properties are strongly temperature and frequency dependent. The plots of Zʹʹ and Mʹʹ versus frequency at various temperatures show peaks in the higher temperature range (>300 o C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.
M. Esthaku Peter; P. Ramasamy
Abstract
Single crystals of triglycinium calcium nitrate, a semiorganic nonlinear optical (NLO) material, have been grown by slow solvent evaporation technique at room temperature. The size of the grown crystal is up to the dimension of 29×19×5 mm 3 . The structure of the crystal was analyzed by single ...
Read More
Single crystals of triglycinium calcium nitrate, a semiorganic nonlinear optical (NLO) material, have been grown by slow solvent evaporation technique at room temperature. The size of the grown crystal is up to the dimension of 29×19×5 mm 3 . The structure of the crystal was analyzed by single crystal X-ray diffraction and the functional groups present in the sample were identified by FTIR spectral analysis in the range 4000-450 cm -1 . The UV-vis-NIR studies was undertaken to find the transmittance in the ultraviolet and visible region. The efficiency of second harmonic generation was analyzed by Kurtz-Perry powder technique and compared with standard KDP crystal. Thermogravimetric and differential thermal analysis have been performed to determine the thermal stability of the crystal. Dielectric properties such as dielectric constant and dielectric loss were studied at various temperatures and frequencies. Vickers microhardness testing was carried out on the as-grown crystal surface to reveal the mechanical properties of the crystal. Etching studies were made on the as grown crystal to analyze the structural imperfection of the crystal.
Nilaya K. Mohanty; Ajay K. Behera; Santosh K. Satpathy; Banarji Behera; Pratibindhya Nayak
Abstract
The Gd-modified BiFeO3-PbTiO3 composites i.e. 0.5BiGdxFe1-xO3-0.5PbTiO3 (BGxF1-x-PT) with x=0.00, 0.05, 0.10, 0.15, 0.20, were prepared by mixed oxide method at high temperature. The structural study reveals that the composites showed tetragonal crystal structure at room temperature and tetragonality ...
Read More
The Gd-modified BiFeO3-PbTiO3 composites i.e. 0.5BiGdxFe1-xO3-0.5PbTiO3 (BGxF1-x-PT) with x=0.00, 0.05, 0.10, 0.15, 0.20, were prepared by mixed oxide method at high temperature. The structural study reveals that the composites showed tetragonal crystal structure at room temperature and tetragonality (c/a ratio) of composites decrease with increase in Gd concentration. The average crystallite size of the composites was found to be in the range of 30-89 nm. Surface morphology of the composites was studied by scanning electron microscopy (SEM). The Goldschmidt tolerance factors of the composites were found to be in the range of 0.989-0.976. The nature of Nyquist plot confirmed the presence of both bulk and grain boundary effects, and non-Debye type of relaxation process occur in the composites. The activation energy of the composites was found to be in the range 0.13-1.38eV. The analyses of ac conductivity data obey the universal agreement with Jonscher’s power law. Further, the explanation of conduction mechanism through correlated barrier hopping (CBH) model was discussed.
S. Amudha; S. Austin Suthanthiraraj
Abstract
The matrix embracing a combination of polyethylene oxide [PEO] as the host polymer component and silver trifluoromethane sulfonate [AgCF3SO3] (also known as silver triflate) as the dopant salt yielding a composite polymer electrolyte [CPE] with varying compositions based on rich contents of Oxygen/Metal ...
Read More
The matrix embracing a combination of polyethylene oxide [PEO] as the host polymer component and silver trifluoromethane sulfonate [AgCF3SO3] (also known as silver triflate) as the dopant salt yielding a composite polymer electrolyte [CPE] with varying compositions based on rich contents of Oxygen/Metal [O/M] ratio has been prepared in the form of thin film specimens using solution casting technique and examined for its application in a solid state battery configuration as a test cell. Such composite polymeric films optimized using electrical conductivity studies have provided realization of a maximum electrical conductivity value of 2.9 ×10 -5 Scm -1 at room temperature (298 K) whereas their temperature-dependent electrical conductivity is found to obey the Arrhenius behavior. Silver ionic transference number (tAg + ) data for these polymeric composites were indomitable using ac/dc polarization technique whereas the occurrence of a transition of phase in accordance with structural and thermal parameters could be investigated by means of X-ray diffraction (XRD) and differential scanning calorimetric (DSC) analyses. The morphological and compositional analyses were carried out by employing scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX) as analytical tools. Electrochemical cells have been fabricated with the common cell configuration Ag|CPE|(I2+G+CPE) and relevant cell parameters evaluated in terms of their discharge characteristics under a constant load of 1 M at room temperature.
M. Chowdhury; S.K. Sharma; R.J. Chaudhary
Abstract
SnO2/Fe2O3 composite thin films were deposited on quartz substrates at various oxygen partial pressures with a substrate temperature of 750 °C by pulsed laser deposition. The structural and optical properties of the deposited films were studied by X-ray diffraction (XRD), Atomic force microscopy ...
Read More
SnO2/Fe2O3 composite thin films were deposited on quartz substrates at various oxygen partial pressures with a substrate temperature of 750 °C by pulsed laser deposition. The structural and optical properties of the deposited films were studied by X-ray diffraction (XRD), Atomic force microscopy (AFM), UV–visible spectroscopy and Photoluminescence. X-ray diffraction analysis revealed the formation of mixed phases (tetragonal SnO2 and hexagonal α-Fe2O3) at lower oxygen partial pressure (0.1 mTorr) and only tetragonal phase at higher oxygen partial pressures (50-250 mTorr). Atomic force microscopy studies show the dense and uniform distribution of composite films. The average RMS roughness of the films increases with increasing oxygen partial pressure. The bandgap was found varying between 3.55 and 3.85 eV for different oxygen pressures. A strong broad blue emission band was observed for all the oxygen partial pressures. The origin of the blue emission in the composite film is discussed with the help of vacancy creation. A correlation between oxygen partial pressure and the properties of SnO2/Fe2O3 .
Vineet Kumar Singh; Jampana Nagaraju
Abstract
This paper presents the effect of emitter thickness and post-annealing process on the conversion efficiency of crystalline silicon (c-Si) solar cells. Diffusion parameters like pre-deposition temperature, drive-in temperature, and process duration assist to control the emitter thickness and inturn improves ...
Read More
This paper presents the effect of emitter thickness and post-annealing process on the conversion efficiency of crystalline silicon (c-Si) solar cells. Diffusion parameters like pre-deposition temperature, drive-in temperature, and process duration assist to control the emitter thickness and inturn improves the conversion efficiency of the solar cells. It is observed that shallower emitter cells have higher conversion efficiency of 10.81% than deeper emitter cells of 7.62%. Post-annealing process at 700 °C for 60 minutes boosts the efficiency of shallower emitter cell from 10.81% to 12.06%. Dark current-voltage characteristics authenticate the formation of p-n junction and also elucidate the presence of recombination saturation current along with diffusion saturation current. Illuminated and dark current-voltage characteristics further provide the evidence that post-annealing process during phosphorus diffusion reduces the trap density and thus the recombination saturation current, which helps to improve the efficiency. The combination of a shallower emitter with post-annealing process provides an excellent approach to enhance the solar cell efficiency.
Vikash Kumar; Swati Kumari; Pawan Kumar; Manoranjan Kar; Lawrence Kumar
Abstract
The correlation between structural and optical properties of nanocrystalline ZnO synthesized by the citrate precursor method has been investigated. The Rietveld refinement of X-ray diffraction pattern confirms the P63mc space group and formation of single phase hexagonal wurtzite structure with presence ...
Read More
The correlation between structural and optical properties of nanocrystalline ZnO synthesized by the citrate precursor method has been investigated. The Rietveld refinement of X-ray diffraction pattern confirms the P63mc space group and formation of single phase hexagonal wurtzite structure with presence of tensile strain at the lattice site. The presence of Raman active optical phonon mode at 436 cm -1 which is a significant character of ZnO with hexagonal wurtzite structure supports the XRD result. FE-SEM result shows that the size of the particle is about 20 nm with nearly spherical shapes. The optical band gap energy at room temperature has been calculated as 3.28 eV using the Tauc plot technique. The UV-Vis sub-gap absorption curve supports the presence of strain inside the crystal. The photoluminescence spectrum indicates the dominancy of the defect related deep level or trap state emissions over the near band edge UV emissions using an excitation wavelength of 320 nm.
Ankur Jain; Pragya Jain; Shivani Agarwal; Paola Gislon; Pier Paolo Prosini; I.P. Jain
Abstract
Magnesium hydride is a promising material for hydrogen storage due to its high storage capacity i.e.7.6wt%. But its high stability i.e. high desorption temperature (~350? o C) limits its practical application towards hydrogen economy. Moreover the kinetics is also too slow even at high temperatures. ...
Read More
Magnesium hydride is a promising material for hydrogen storage due to its high storage capacity i.e.7.6wt%. But its high stability i.e. high desorption temperature (~350? o C) limits its practical application towards hydrogen economy. Moreover the kinetics is also too slow even at high temperatures. Composite formation with Zr based laves phase alloys, especially ZrCr2 family, is an effective method to improve the hydriding properties of MgH2. This work presents the synthesis, structural, morphological, and hydrogenation properties of Mg-x wt% ZrCrMn composites. Both phases i.e. Mg & ZrCrMn remain their presence after milling and several hydriding cycles as well. SEM results suggest the homogeneous distribution of alloy particles on Mg matrix. Pressure composition temperature (PCT) analysis shows a reduction in desorption temperature down to 250 o C for these composites. TG experiments suggest a total hydrogen capacity of 5.9% and 4.35% for x =25, 50 in Mg-x wt% ZrCrMn composites respectively. The enthalpy of hydride formation is also calculated using Van’t Hoff plots, which is found similar to the parent material i.e. MgH2. A remarkable enhancement in the kinetics of hydrogen absorption / desorption is reported here by forming these composites.
Arvind Kumar; S. K. Mishra
Abstract
In the present work, detailed investigation of dielectric, piezoelectric and ferroelectric properties of Nb and Fe co-doped PZT ceramic near the MPB composition has been carried out. Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 (PFZTN) ceramics for x = 1- 6 mol% and y = 5.50 mol% have been prepared by a semi-wet ...
Read More
In the present work, detailed investigation of dielectric, piezoelectric and ferroelectric properties of Nb and Fe co-doped PZT ceramic near the MPB composition has been carried out. Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 (PFZTN) ceramics for x = 1- 6 mol% and y = 5.50 mol% have been prepared by a semi-wet route. X-ray diffraction studies confirm the formation of single phase perovskite structure. It is shown that Fe doping in PZNT improves the dielectric, ferroelectric and piezoelectric properties of ceramics. It has been found that at room temperature, dielectric constant and d33 start to increase up to the composition x = 0.05 and thereafter decrease. The maximum value of dielectric constant and d33 has been found for the composition x = 0.05. It has been shown that doping of Fe does not affect over the transition temperature uptown x = 0.04. The value of remnant polarization is of the order of 11.62 µC/cm 2 at x= 0.04. The investigated material seems to be promising candidate for multilayer capacitor applications.
M. Roy; S. Sahu; S. K. Barbar; S. Jangid
Abstract
Polycrystalline ceramic samples of pure and Cu +2 doped Bi4V2-xCuxO11(x=0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The dielectric constant and dielectric loss and hence ac conductivity as a function of frequency and temperature have been measured. ...
Read More
Polycrystalline ceramic samples of pure and Cu +2 doped Bi4V2-xCuxO11(x=0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The dielectric constant and dielectric loss and hence ac conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy and hence its ac conductivity increases with the increase of temperature. The dc conductivity of material has been measured as a function of temperature from room temperature to 653 K and its activation energy was calculated using the relation σ = σo exp (- Ea/kT). The dc conductivity increases with the substitution of Cu on the vanadium site. The Modulated Differential Scanning Calorimetry (MDSC) has been used to investigate the effect of substitution on the phase transition of the compounds. The results are discussed in detail.
B. C. Sutar; Piyush R. Das; R. N. P. Choudhary
Abstract
Lead-free polycrystalline material Sr(Bi0.5V0.5)O3 was prepared using a high- temperature solid state reaction technique (calcinations and sintering temperature =850 and 950 o C, respectively) using high-purity ingredients. The formation of the material in the monoclinic crystal structure was confirmed ...
Read More
Lead-free polycrystalline material Sr(Bi0.5V0.5)O3 was prepared using a high- temperature solid state reaction technique (calcinations and sintering temperature =850 and 950 o C, respectively) using high-purity ingredients. The formation of the material in the monoclinic crystal structure was confirmed by preliminary X-ray structural analysis with room temperature data.The nature of microstructure obtained by scanning electron microscopy (SEM) shows that the compound has well defined grains which are uniformly distributed throughout the surface of the sample. Detailed studies of dielectric and impedance properties of the material carried out in the frequency range of 1 kHz –1MHz at different temperatures (30 0 C to 455 0 C) have provided many interesting properties. Detailed studies of dielectric properties of the compound showed an existence of diffus e phase transition around 258 0 C. The temperature dependence of electrical parameters (impedance, modulus etc.) of the material exhibits a strong correlation of its microstructure with the electrical parameters. The negative temperature coefficient of resistance (NTCR) behavior also was observed in the material. The complex electric modulus analysis indicates the presence of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The nature of variation of dc conductivity with temperature confirms the Arrhenius behavior of the material. The ac conductivity spectra show a typical signature of an ionic conducting system, and are found to obey Jonscher’s universal power law.
S. Behera; Piyush R. Das; B. N. Parida; P. Nayak; R. N. P Choudhary
Abstract
The polycrystalline sample of complex tungsten-bronze compound Li2Pb2Sm2W2Ti4Ta4O30 was prepared by a high-temperature solid-state reaction technique. Room temperature X-ray diffraction (XRD) study suggests the formation of a single-phase compound. Microstructure of the pellet sample was studied by scanning ...
Read More
The polycrystalline sample of complex tungsten-bronze compound Li2Pb2Sm2W2Ti4Ta4O30 was prepared by a high-temperature solid-state reaction technique. Room temperature X-ray diffraction (XRD) study suggests the formation of a single-phase compound. Microstructure of the pellet sample was studied by scanning electron microscope. The temperature variation of dielectric constant shows dielectric anomaly in the sample. Study of electrical properties (impedance, conductivity, etc.,) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc) and electrical parameters. A typical Arrhenius behavior was observed in the temperature dependence of dc conductivity.
Poorva Sharma; Dinesh Varshney
Abstract
La/Pb co-doped BiFeO3 compounds were prepared by a solid-state reaction. X-ray diffraction of BiFeO3 (BFO), Bi0.725La0.1Pb0.175FeO3 [BLPFO] showed single phase in nature. BFO crystallize in the rhombohedral distorted perovskite structure (space group-R3c) while to that BLPFO crystallize in distorted ...
Read More
La/Pb co-doped BiFeO3 compounds were prepared by a solid-state reaction. X-ray diffraction of BiFeO3 (BFO), Bi0.725La0.1Pb0.175FeO3 [BLPFO] showed single phase in nature. BFO crystallize in the rhombohedral distorted perovskite structure (space group-R3c) while to that BLPFO crystallize in distorted pseudocubic (Pm-3m) symmetry which has been confirmed by the Rietveld refinement of the room temperature X-ray powder diffraction data. The effect of La/Pb substitution on dielectric constant, and loss tangent, of the samples was studied at room temperature in a wide range of frequency 10 Hz – 1 MHz. The room temperature dielectric constant of BFO (BLPFO) was 120 (200). Ferroelectric measurement reveals remnants polarization of BLPFO is about 0.24 μC/cm 2 at an applied field of 15 kV/cm. Weak ferroelectric effect is observed for co-doped BiFeO3 compound.
K. K. Bamzai; Rashmi Gupta; Shivani Suri; Vishal Singh
Abstract
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, ...
Read More
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, mechanical and electrical investigations using various chemical and physical methods. X - ray diffraction analysis (XRD) establishes magnesium hydrogen phosphate and cadmium magnesium hydrogen phosphate belonging to orthorhombic crystal system with space group Pbca. The mechanical behaviour of these crystals was studied by calculating Vicker’s hardness number. The behaviour of microhardness with applied load was observed to be complex. The electrical behaviour was carried out by calculating dielectric constant at different temperatures and for different frequencies. The dielectric constant (ε/) was found to be strongly dependent on temperature and frequency. The transition metal doping of cadmium in magnesium hydrogen phosphate remarkably decrease the value of dielectric constant from 68 to 23. The transition temperature also decreases from 330ËšC in case of magnesium hydrogen phosphate to 310ËšC in case of cadmium magnesium hydrogen phosphate.
P. S. Sahoo; B. B. Mohanty; R. N. P. Choudhary
Abstract
The advent of nanoscience & technology have completely changed the orientation/direction of studies of eco-friendly (lead-free) materials bringing them at the forefront of scientific developments with considerably enhanced physical properties suitable for a wide variety of challenging applications. ...
Read More
The advent of nanoscience & technology have completely changed the orientation/direction of studies of eco-friendly (lead-free) materials bringing them at the forefront of scientific developments with considerably enhanced physical properties suitable for a wide variety of challenging applications. Barium based ferroelectric materials have gained much importance due to their vast applications as they possess high dielectric constant, non-linear spontaneous polarization, negative temperature coefficient of resistance behavior etc.. All these characteristics stimulated the researchers to replace toxic and hazardous lead based materials by barium based TB materials from industry. Our present research work deals with the synthesis of polycrystalline samples of Ba2Sr3RTi3V7O30 (R = Gd, Sm) by a high temperature solid state reaction technique and a comparative study of the electrical properties of the samples. Preliminary structural (XRD) analyses of these compounds show the formation of single-phase orthorhombic structures at room temperature having average crystallite size of the order of some nanometer for both the compounds. The electrical properties for both the samples are studied in a wide range of temperature (30–500 o C) and frequency (100Hz-1MHz). The dielectric properties suggest that both the compounds have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 230 and 313 0 C for R= Sm and Gd respectively at frequency 100 kHz).The bulk resistance of the materials exhibits negative temperature coefficient of resistance behavior as observed in semiconductors.
M. Raghasudha; D. Ravinder; P. Veerasomaiah
Abstract
Nano-ferrites of the composition Mg Crx Fe2-xO4 (where x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized at a very low temperature (180°C) by Citrate-gel auto combustion method. The as synthesized powders were sintered at 500 0 C for four hours in an air and were characterized by X-ray diffraction ...
Read More
Nano-ferrites of the composition Mg Crx Fe2-xO4 (where x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) were synthesized at a very low temperature (180°C) by Citrate-gel auto combustion method. The as synthesized powders were sintered at 500 0 C for four hours in an air and were characterized by X-ray diffraction (XRD) which confirmed the formation of cubic spinel structure of ferrites. The crystallite size was in the range of 7 to 23nm for different compositions with the significant decrease of ~16nm in response to the increase in Cr substitution. Such low nano sized ferrites are desirable for variety of applications like, in magnetic data storage and in targeted drug delivery, etc. Morphological studies by Scanning Electron Microscopy (SEM) revealed formation of largely agglomerated, well defined nano particles of the sample. Elemental composition characterizations of the prepared samples were performed by Energy Dispersive Spectroscopy (EDS) which shows the presence of Mg, Cr, Fe and O without precipitating cations. The FTIR spectral studies at room temperature in the range of 400 to 800cm-1 showed two strong absorption bands. The high frequency band (ν1) around 600 cm -1 is attributed to the intrinsic vibrations of tetrahedral complexes and the low frequency band (ν2) around 400 cm -1 is due to octahedral complexes. The spectra showed the characteristic peaks of ferrite sample. The observed results can be explained on the basis of composition and crystal size.
Usha Chandra; K. Asokan; V. Ganesan
Abstract
Nanocrystalline stoichiometric La0.8Sr0.2Mn0.8Fe0.2O3 manganites synthesized by sol gel technique were irradiated by 200 MeV Ag +16 ion beam at various fluences and investigated by X-ray diffraction (XRD), magnetization and high resolution Mössbauer spectroscopic techniques. The analysis of Mössbauer ...
Read More
Nanocrystalline stoichiometric La0.8Sr0.2Mn0.8Fe0.2O3 manganites synthesized by sol gel technique were irradiated by 200 MeV Ag +16 ion beam at various fluences and investigated by X-ray diffraction (XRD), magnetization and high resolution Mössbauer spectroscopic techniques. The analysis of Mössbauer patterns were done using Kopcewicz et al. (2004) proposition considering Double exchange mechanism. Both XRD and Mössbauer spectroscopic analysis indicated isostructural vacancy formation at Mn site at the fluence 5x10 12 ions/cm 2 . The system showed amorphous phase at the higher fluence of 1x10 13 ions/cm 2 . The local electronic environments seen through high resolution Mössbauer spectroscopic technique on the irradiated systems were understood in terms of ferromagnetic coupling between different Mn environment surrounding Fe ions. This proposition is supported by enhanced magnetization observed in the irradiated samples (Kopcewicz et al., 2004). The similarity to the hydrostatic applied pressure (at low value) is seen through the transformation from Fe 4+ to Fe 3+ at low fluence.
Gagan Kumar; Ritu Rani; Vijayender Singh; Sucheta Sharma; Khalid M. Batoo; M. Singh
Abstract
Co 2+ substituted Mg-Mn nanoferrites having formulae Mg0.9Mn0.1CoxFe2-xO4, where x = 0.0, 0.1, 0.2 & 0.3, have been prepared for the first time by solution combustion technique. The magnetic properties of nanoferrites such as M-H, initial permeability (μi) and magnetic loss tangent (tan δ) ...
Read More
Co 2+ substituted Mg-Mn nanoferrites having formulae Mg0.9Mn0.1CoxFe2-xO4, where x = 0.0, 0.1, 0.2 & 0.3, have been prepared for the first time by solution combustion technique. The magnetic properties of nanoferrites such as M-H, initial permeability (μi) and magnetic loss tangent (tan δ) have been investigated as a function of frequency in the range 700 Hz to 30 MHz. X-ray diffraction patterns confirmed the formation of single phase spinel structure of all the nanoferrites. The surface morphology of the samples is studied by using scanning electron microscopy (SEM), while elemental compositions of samples are studied by energy dispersive X-ray analysis (EDAX). Saturation magnetization (Ms) and magneto-crystalline anisotropy constant (K1) are found to be increasing with an increase in cobalt content while initial permeability and magnetic loss tangent are found to be decreasing with an increase in frequency as well as with the increasing concentration of Co 2+ ions. The very low values of magnetic loss tangent even at high frequencies are the prime achievements of the present work.
Pradip Z. Zambare; K. V. R. Murthy;O. H. Mahajan; K. D. Girase
Abstract
In this paper we report Strontium Cerium Oxide (Sr2CeO4) blue phosphor was synthesized via solid state reaction method using strontium carbonate SrCO3 and cerium oxide CeO2 as raw materials. The samples were characterized by Thermo analytical techniques (TG, DTA, DTG and DSC) in nitrogen atmosphere, ...
Read More
In this paper we report Strontium Cerium Oxide (Sr2CeO4) blue phosphor was synthesized via solid state reaction method using strontium carbonate SrCO3 and cerium oxide CeO2 as raw materials. The samples were characterized by Thermo analytical techniques (TG, DTA, DTG and DSC) in nitrogen atmosphere, Fourier transformation infrared (FTIR) spectroscopy, and Photoluminescence at room temperature. Thermal analysis indicates that Sr2CeO4 phosphor can be prepared at temperature higher than 1100 °C. In excitation spectra two excitation peaks were located at 262 and 399 nm respectively. The emission spectrum was a broad band peaking at 470 nm, which was suitable for the doping of rare earth ions. The color co-ordinates for the pure Sr2CeO4 were x = 0.1918 and y = 0.2483. This material has potential for applications in the field of emission devices.
K. Kaviyarasu; Prem Anand Devarajan
Abstract
In this work we report the successful formation of hexagonal pillar shaped ZnO nanoneedles with high yield and by using simple cheap method with CTAB as the surfactant. SEM and TEM microscopic observation revealed that the ZnO nanorods were smooth and uniform throughout their length and the functional ...
Read More
In this work we report the successful formation of hexagonal pillar shaped ZnO nanoneedles with high yield and by using simple cheap method with CTAB as the surfactant. SEM and TEM microscopic observation revealed that the ZnO nanorods were smooth and uniform throughout their length and the functional groups in the molecule were identified by FTIR analysis. PL properties of ZnO nannorods were found to be dependent on the growth condition and the resultant morphology revealed that ZnO nanorods were highly transparent in the visible region.
Ch. Atchyutha Rao; Poornachandra Rao V. Nannapaneni; K. V. R. Murthy
Abstract
In this paper we report the synthesis and luminescence of strontium cerium oxide (Sr2CeO4:Eu 3+ (0.5mol%),La 3+ (0.5mol%) prepared by solid state reaction method in air at 12000C.These samples were characterized by X-ray diffraction, scanning electron microscope (SEM) and photoluminescence (PL) techniques, ...
Read More
In this paper we report the synthesis and luminescence of strontium cerium oxide (Sr2CeO4:Eu 3+ (0.5mol%),La 3+ (0.5mol%) prepared by solid state reaction method in air at 12000C.These samples were characterized by X-ray diffraction, scanning electron microscope (SEM) and photoluminescence (PL) techniques, particle size analysis. The photo luminescence (PL) spectra of pure and Eu 3+ , La 3+ codoped Sr2CeO4 were recorded at room temperature. Sr2CeO4 phosphor was effectively excited around 250 nm and observed a broad emission band peak around 467 nm. XRD data revealed that the structure of Sr2CeO4 is orthorhombic, and the mean crystallite size of Sr 2CeO4 and Sr2CeO4: Eu 3+ , La 3+ were 9 nm and 11nm respectively. The colour co-ordinates of Sr2CeO4 were x = 0.16 and y = 0.18 and CIE co-ordinates revealed that the present phosphors may be used in white light applications.