Md. Fakhrul Islam

Characterization of Ni–Cu mixed spinel ferrite

Abstract Crystal structure, X-ray density, porosity, compressive strength of Ni 1− x Cu x Fe 2 O 4 have been investigated along with scanning electron microscopy (SEM) to study the effect of composition and microstructure on the magnetic and electrical properties. The formation of single-phase ferrite is confirmed by the X-ray diffraction. Tetragonal deformation is observed for the sample of composition x =1, i.e. for pure CuFe 2 O 4 Crystal structure for samples of other compositions are face centered cubic (FCC). SEM micrographs exhibit increase in grain size with the increase of copper content. Compressive strength decreases with the increase of Cu. Initial magnetic permeability and saturation magnetization is maximum for the composition of x =0.2, i.e. for Ni 0.8 Cu 0.2 Fe 2 O 4 , which can be attributed to the maximum sintered density obtained for this composition. Resistivity decreases with the increase of Cu content.

Size dependent magnetic and electrical properties of Ba-doped nanocrystalline BiFeO3

Improvement in magnetic and electrical properties of multiferroic BiFeO3 in conjunction with their dependence on particle size is crucial due to its potential applications in multifunctional miniaturized devices. In this investigation, we report a study on particle size dependent structural, magnetic and electrical properties of sol-gel derived Bi0.9Ba0.1FeO3 nanoparticles of different sizes ranging from ∼ 12 to 49 nm. The substitution of Bi by Ba significantly suppresses oxygen vacancies, reduces leakage current density and Fe2+ state. An improvement in both magnetic and electrical properties is observed for 10 % Ba-doped BiFeO3 nanoparticles compared to its undoped counterpart. The saturation magnetization of Bi0.9Ba0.1FeO3 nanoparticles increase with reducing particle size in contrast with a decreasing trend of ferroelectric polarization. Moreover, a first order metamagnetic transition is noticed for ∼ 49 nm Bi0.9Ba0.1FeO3 nanoparticles which disappeared with decreasing particle size. The observed stro...

Dy doped BiFeO3: A bulk ceramic with improved multiferroic properties compared to nano counterparts

Abstract The synthesis as well as structural, multiferroic and optical characterization of Dy doped BiFeO3 multiferroic ceramic are presented. Bulk polycrystalline Bi 0.9 Dy 0.1 FeO 3 sample is synthesized by solid state reaction, while their nano counterparts are prepared using ultrasonic probe sonication technique. Significant improvement of phase purity in the as synthesized samples is observed after the doping of Dy both in bulk Bi 0.9 Dy 0.1 FeO 3 sample and corresponding nanoparticles as evidenced from Rietveld refinement. Magnetization measurements using SQUID magnetometer exhibit enhanced magnetic properties for Dy doped bulk Bi 0.9 Dy 0.1 FeO 3 ceramic compared to their nanostructured counterparts as well as undoped BiFeO3. Within the applied field range, saturation polarization is observed for Bi 0.9 Dy 0.1 FeO 3 bulk ceramic only. As a result, intrinsic ferroelectric behavior is obtained just for this sample. Optical bandgap measurements reveal lower bandgap for Dy doped bulk Bi 0.9 Dy 0.1 FeO 3 ceramic compared to that of corresponding nanoparticles and undoped BiFeO3. The outcome of this investigation demonstrates the potential of Dy as a doping element in BiFeO3 that provides a bulk ceramic material with improved multiferroic and optical properties compared to those of corresponding nanoparticles which involve rigorous synthesis procedure.

Effect of Sintering Parameters and Ta2O5 Doping on the Microstructure and Dielectric Properties of BaTiO3 Based Ceramics

The main focus of the research was to correlate the composition and sintering parameters with the microstructure and dielectric properties of Ta2O5 (Tantalum Oxide) doped BaTiO3 (Barium Titanate) ceramics. Ta2O5 was doped at three different percentages viz. 0.5, 1.0 and 1.5 mole%. The doped samples were then sintered using both single and double stage sintering techniques. Thereafter field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) techniques were used to examine the structure of the samples with particular focus on the incorporation of Ta5+ions into the BaTiO3 crystal lattice. Finally, the dielectric properties were analyzed using impedence analyzer and the relationship between the properties and structure of doped BaTiO3 was established. From the research, it can be stated that double stage sintering yielded best dielectric properties. The best stable value of room temperature dielectric constant (k) of 19000 was obtained for 1.5mole % Ta2O5 doped BaTiO3 sample, sintered at 1320°C for 0 hour and 1280°C for 6 hours due to the combination of high percent theoretical density (%TD) and optimum grain size. At a temperature range of 30°C to 60°C, this combination of composition and sintering parameters yielded dielectric constant in the range of 18000-19000.

Development of Ceramic Candle Filters by Slip Casting Process

A well-defined porous ceramic having effective pore size less than 1 µm was fabricated by slip casting technique which provides a low-cost and single-stage filtration process. This single-stage filtration process removed suspended solids and pathogenic organism. In this study, diatomaceous earth was used as pore forming agent in clay based ceramic body. Varied amount of diatomaceous earth was used with fixed proportion of china clay, ball clay and lime stone. X-ray fluorescence spectroscopy (XRF) was used to determine the composition of raw materials and final sintered filter body. In terms of porosity and flow rate, 25% diatomaceous earth shows better filtration property. It was found that total porosity increased with decreasing milling time. As the firing temperature increased, porosity decreased rapidly after 1100 °C. However, the change of porosity in firing range of 1000 °C–1100 °C was found very small. Mercury intrusion porosimetry was used to measure the pore size and its distribution. An effective intra-particle pores in a range of 0.2-0.5 μm was identified. Inter- and intra-particle pores were observed using scanning electron microscope (SEM). Microbial removalefficiency of 99.99% was measured, while water flow rate was found in a range of 200-700 ml/hour.

Bandgap Tuning of Sm and Co Co-doped BFO Nanoparticles for Photovoltaic Application

Multiferroic

Structure-property relationship in high-tension ceramic insulator fired at high temperature

BiFeO_3

Saturation magnetization and band gap tuning in BiFeO3 nanoparticles via co-substitution of Gd and Mn

BiFeO3 (BFO) with bandgap energy (