D. Paul Joseph

Room temperature dual ferroic behaviour of ball mill synthesized NdFeO3 orthoferrite

Phase pure NdFeO3 has been achieved using high energy ball milling of oxide precursors with subsequent sintering. It is established that structural arrangement of NdFeO3 regulates the multifunctional feature of the material. Rietveld refinement of the room temperature X-ray diffraction pattern shows that the Fe-O-Fe bond angle significantly favors the super exchange interaction, which is predominantly antiferromagnetic in nature. Magnetization measurement illustrates antiferromagnetic behaviour with a weak ferromagnetic component caused by the canted nature of the Fe3+ spins at room temperature. Absorption bands in the visible ambit, apparent from the UV-Vis diffuse reflectance studies, is found due to the crystal ligand field of octahedral oxygen environment of Fe3+ ions. The direct band gap is estimated to be 2.39u2009eV from the diffuse reflectance spectrum. The lossy natured ferroelectric loop having a maximum polarization of 0.23u2009μC/cm2 at room temperature is found to be driven by the non-collinear magne...

Intense violet–blue emission and paramagnetism of nanocrystallineGd 3+ doped ZnO ceramics

Nanocrystalline Zn1-xGdxO (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were synthesized by ball milling and subsequent solid-state reaction. The transmission electron microscopy (TEM) micrograph of as synthesized samples revealed the formation of crystallites with an average diameter of 60 nm, and the selected area electron diffraction (SAED) pattern confirmed the formation of wurtzite structure. A red shift in the band gap was observed with increasing Gd3+ concentration. The photoluminescence of nanocrystalline Gd3+ doped ZnO exhibited a strong violet–blue emission. Concentration dependence of the emission intensity of Gd3+ in ZnO was studied, and the critical concentration was found to be 4 mol% of Gd3+. The Gd3+ doped ZnO exhibited paramagnetic behavior at room temperature, and the magnetic moment increased with Gd3+ concentration.

Investigation of the Less Oxygen Deficient SrFeO3‐δ

Perovskite type SrFeO3 is a suitable candidate for gas sensors and catalytic applications. It is very difficult to stabilize the stoichiometric SrFeO3, which is highly unstable because of the presence of Fe4+ ions that leads to the oxygen vacancies (δ) in order to maintain charge equilibrium. For δu2009=u20090, 0.13, 0.27 and 0.5, it takes SrFeO3, SrFeO2.87, SrFeO2.73 and SrFeO2.5 phases respectively. The oxygen vacancy plays an important role in determining its structural and electronic properties. Nanocrystalline SrFeO3 has been prepared by thermal decomposition method and its structural, morphological, magnetic and electrical properties are analyzed.

Synthesis and Characterization of BiMn2O5 Ceramics

BiMn 2 O 5 , prepared by high energy ball milling of precursor oxides followed by sintering at 900° C for 24 h, has been investigated for its magnetic and electrical properties. The XRD pattern reveals orthorhombic phase with Pbam space‐group. Magnetization measurements show a paramagnetic behaviour at room temperature with a Neel transition at 40 K. Electrical conductivity studies show room temperature resistivity value around 9×10 5 Ω cm .

Fabrication and stability investigation of ultra-thin transparent and flexible Cu-Ag-Au tri-layer film on PET

The need for transparent conducting electrodes with high transmittance, low sheet resistance and flexibility to replace Indium Tin Oxide is ever growing. We have deposited and studied the performance of ultra-thin Cu-Ag-Au tri-layer films over a flexible poly-ethylene terephthalate substrate. Scotch tape test showed good adhesion of the metallic film. Transmittance of the tri-layer was around 40 % in visible region. Optical profiler measurements were done to study the surface features. The XRD pattern revealed that film was amorphous. Sheet resistance measured by four probe technique was around 7.7 Ohm/Δ and was stable up to 423u2005K. The transport parameters by Hall effect showed high conductivity and carrier concentration with a mobility of 5.58u2005cm2/Vs. Tests performed in an indigenously designed bending unit indicated the films to be stable both mechanically and electrically even after 50,000 bending cycles.The need for transparent conducting electrodes with high transmittance, low sheet resistance and flexibility to replace Indium Tin Oxide is ever growing. We have deposited and studied the performance of ultra-thin Cu-Ag-Au tri-layer films over a flexible poly-ethylene terephthalate substrate. Scotch tape test showed good adhesion of the metallic film. Transmittance of the tri-layer was around 40 % in visible region. Optical profiler measurements were done to study the surface features. The XRD pattern revealed that film was amorphous. Sheet resistance measured by four probe technique was around 7.7 Ohm/Δ and was stable up to 423u2005K. The transport parameters by Hall effect showed high conductivity and carrier concentration with a mobility of 5.58u2005cm2/Vs. Tests performed in an indigenously designed bending unit indicated the films to be stable both mechanically and electrically even after 50,000 bending cycles.

Electrical transport properties of spray deposited transparent conducting ortho-Zn2SnO4 thin films

Ortho Zinc Stannate (Zn2SnO4) exhibits excellent electrical and optical properties to serve as alternate transparent electrode in optoelectronic devices. Here we have optimized ortho-Zn2SnO4 thin film by spray pyrolysis method. Deposition was done onto a pre-heated glass substrate at a temperature of 400 °C. The XRD pattern indicated films to be polycrystalline with cubic structure. The surface of films had globular and twisted metal sheet like morphologies. Films were transparent in the visible region with band gap around 3.6 eV. Transport properties were studied by Hall measurements at 300u2005K. Activation energies were calculated from Arrhenius’s plot from temperature dependent electrical measurements and the conduction mechanism is discussed.Ortho Zinc Stannate (Zn2SnO4) exhibits excellent electrical and optical properties to serve as alternate transparent electrode in optoelectronic devices. Here we have optimized ortho-Zn2SnO4 thin film by spray pyrolysis method. Deposition was done onto a pre-heated glass substrate at a temperature of 400 °C. The XRD pattern indicated films to be polycrystalline with cubic structure. The surface of films had globular and twisted metal sheet like morphologies. Films were transparent in the visible region with band gap around 3.6 eV. Transport properties were studied by Hall measurements at 300u2005K. Activation energies were calculated from Arrhenius’s plot from temperature dependent electrical measurements and the conduction mechanism is discussed.

100 MeV O7+ irradiation induced red shift in the band gaps of 3 wt% 'Li' doped Nb2O5 thin film

Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass substrate at 350 °C is irradiated with 100 MeV O7+ ion at a fluence of 5×1012 ions/cm2. X-ray diffraction shows that the pristine and irradiated films are polycrystalline with a tetragonal phase. Raman peaks suppressed upon irradiation imply large surface degradation which is also seen as a decrement in transparency in visible region to one half of the pristine film. Large red shift is observed in direct and indirect band gaps upon irradiation. Hall effect reveals slight increase in carrier concentration due to irradiation induced defects.Nb2O5:Li (3 wt%) thin film of thickness 353 nm spray deposited onto ITO coated glass substrate at 350 °C is irradiated with 100 MeV O7+ ion at a fluence of 5×1012 ions/cm2. X-ray diffraction shows that the pristine and irradiated films are polycrystalline with a tetragonal phase. Raman peaks suppressed upon irradiation imply large surface degradation which is also seen as a decrement in transparency in visible region to one half of the pristine film. Large red shift is observed in direct and indirect band gaps upon irradiation. Hall effect reveals slight increase in carrier concentration due to irradiation induced defects.

Comparison of Properties of Pristine and 200 MeV Ag15+ Ions Irradiated ‘Li’ 3 wt% Doped V2O5 Thin Films

Lithium (3 wt%) doped V2O5 thin film of thickness 97xa0nm was spray deposited over an ITO coated glass substrate at 450xa0°C. The deposited film was irradiated with 200xa0MeV Ag15+ swift heavy ions (SHI) at a fluence of 5xa0×xa01012 ions/cm2. X-ray diffraction reveals the pristine and irradiated films to have an orthorhombic phase. The SHI irradiation induced thermal spike lead to texturing along the (400) direction along with partial amorphization. The 394xa0cm−1 O–V–O Raman bending deformation is suppressed due to SHI irradiation induced oxygen vacancies. Optical transparency decreased from 80 to 50xa0% and the direct and indirect band gaps showed red shift upon SHI irradiation. Hall effect study revealed marginal variation in transport parameters upon SHI irradiation. The results are discussed.

Synthesis and Characterization of BiMn2O5Ceramics

BiMn 2 O 5 , prepared by high energy ball milling of precursor oxides followed by sintering at 900° C for 24 h, has been investigated for its magnetic and electrical properties. The XRD pattern reveals orthorhombic phase with Pbam space‐group. Magnetization measurements show a paramagnetic behaviour at room temperature with a Neel transition at 40 K. Electrical conductivity studies show room temperature resistivity value around 9×10 5 Ω cm .

Synthesis and Characterization of BiMn[sub 2]O[sub 5] Ceramics

BiMn 2 O 5 , prepared by high energy ball milling of precursor oxides followed by sintering at 900° C for 24 h, has been investigated for its magnetic and electrical properties. The XRD pattern reveals orthorhombic phase with Pbam space‐group. Magnetization measurements show a paramagnetic behaviour at room temperature with a Neel transition at 40 K. Electrical conductivity studies show room temperature resistivity value around 9×10 5 Ω cm .