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Papers by Mohammad Nazmul Hossain

Bull. Mater. Sci., 2019

The bandgap energy range of multiferroic bismuth ferrite is 2.2-2.7 eV, making it a promising can... more The bandgap energy range of multiferroic bismuth ferrite is 2.2-2.7 eV, making it a promising candidate for photovoltaic (PV) applications. But its efficiency is still very low (<2%). This report thus focusses on the application of bismuth ferrite (BFO) engineered with cobalt (Co) doping and on the tuning of its bandgap energy (E g). BiFeO 3 is a unique multiferroic material that simultaneously displays both ferromagnetic and ferroelectric properties at room temperature. Co doped with pure BiFeO 3 (BiFe (1−x) Co x O 3 ; x = 0, 0.05, 0.1 and 0.15) was synthesized by the sol-gel method and annealed at 600 • C. X-ray diffraction shows the well-arranged crystalline structure and peaks of pure and doped-BiFeO 3 nanoparticles. A suitable reduction of E g has been observed for Co-doped BiFeO 3 , which may be appropriate for the effective use in PV solar cells. Thermogravimetric analysis and differential scanning calorimetry were used to investigate the thermal decomposition character of the xerogel powder and the pattern of pure and doped BiFeO 3 phases. Field emission scanning electron microscopy images show the surface crystallography of pure and Co-doped BiFeO 3. Co-doped BiFeO 3 has considerably reduced the crystallite and particle size of the samples. We have calculated the E g of pure and doped BiFeO 3 using a UV-Vis-NIR spectrophotometer and the results show the important reduction of E g (1.60 eV) of the Co-doped samples, which may have potential applications in PV solar cells.

Journal of Electronic Materials, 2018

Multiferroic BiFeO 3 (BFO) with bandgap energy (E g ) between 2.2 eV to 2.7 eV is a potential can... more Multiferroic BiFeO 3 (BFO) with bandgap energy (E g ) between 2.2 eV to 2.7 eV is a potential candidate for photovoltaic (PV) application. However, the efficiency of BFO based PV solar cells is reportedly still too low (less than 2%) to be used for practical applications. Reducing E g of BFO without compromising the ferroelectric properties is a big challenge to the scientific community to obtain power conversion efficiencies beyond the maximum value of 26.6% reported in general for silicon based hetero-structure PV solar cells. In this context, samarium (Sm) and cobalt (Co) co-doped BFO (Bi 0:9 Sm 0:1 Fe 0:9 Co 0:1 O 3 ) nanoparticles were synthesized using the sol-gel method. X-ray diffractometry was employed to determine the structure of synthesized nanoparticles. A welldefined crystalline structure of co-doped BFO nanoparticles was confirmed. Field emission scanning electron microscopy was carried out to study grain morphology of synthesized nanoparticles. Sm and Co dopants have been shown to reduce grain size significantly from 68.3 nm to 18.5 nm. An UV-Vis-NIR spectrophotometer was used to measure diffuse reflectance to calculate E g . A significant reduction of E g down to 1.50 eV of co-doped BFO compared to undoped and or single doped counterpart has been manifested.

Transaction on electrical and electronic materials, 2019

Sol-gel as a chemical solution deposition technique is compatible with functional device fabricat... more Sol-gel as a chemical solution deposition technique is compatible with functional device fabrication technology. Single-phase bismuth ferrite (BiFeO 3) mutiferroic with its multi-functionality has extensively been studied for a variety of prospective novel device applications. However, the synthesis of BiFeO 3 is confronted with a challenge to produce pure state without any secondary phase. Scarcity of unified process parameters impede justification of best synthesis techniques. In this work, sol-gel methods with and without auto-combustion reactions were used to synthesize bismuth ferrite (BiFeO 3) nanoparticles. Different techniques UV-Vis-NIR spectroscopy, XRD, EDS, and SEM were used to investigate the effect of preparation routes on the crystal purity and properties of prepared samples. Synthesized nanoparticles were calcined at temperature between 400 and 800 • C and an optimal calcination temperature was found to be 600 • C. Band-gap was determined by UV-Vis-NIR spectroscopy and found to vary from 1.93 to 2.07 eV. X-ray diffraction (XRD) has confirmed single phase rhombohedral crystal structure with R3c symmetry. Avg crystallite size was found to be higher (40-68 nm) in auto-combustion reaction compared to that of 23-42 nm obtained in sol-gel method without auto-combustion reaction. The band-gap energy was found to reduce with decreasing crystallite size (above the critical size of 10 nm) following Brus's effective mass model. Induced strain was found to exhibit an inverse relation with crystallite size and displayed substantial reduction in auto-combustion reaction route. The microstructural features were investigated by field emission scanning electronic microscopy and avg particle size was shown to vary from 107 to 197 nm depending on adopted synthesis route. A low reaction temperature (70 • C-80 • C) without auto-combustion and calcination temperature at 600 • C were found to be optimal conditions for the preparation of low impurity un-doped bismuth ferrite nanaoparticles.

Materials Research Express, 2019

In this work, Gd and Cr co-doped Bi 0.95 Gd 0.05 Fe 1−x Cr x O 3 (x = 0-0.08) functional ceramics... more In this work, Gd and Cr co-doped Bi 0.95 Gd 0.05 Fe 1−x Cr x O 3 (x = 0-0.08) functional ceramics were synthesized by chemical solution deposition technique (CDS). The synthesized samples were annealed at different temperatures between 400-700 • C. The X-ray diffrac-tion (XRD) study revealed a partial phase evolution from R3c (rhombohedral) crystal structure to pna2 1 crystal structure (orthorhombic) with Gd doping which further enhanced with increasing Cr co-doping. XRD analysis has shown a significant reduction in crystallite size to 25 nm from 68 nm of un-doped BiFeO 3. Field Emission Scanning Electron Microscopy (FESEM) exhibited more uniform nanoparticles due to doping effects and the average size of particle was found to be higher compared to that obtained from XRD results. The magnetic measurement showed a significant improvement in ferromagnetic properties of the synthesized samples, in particular, an enhanced magnetization was obtained for 5 at.% Gd + 6 at.% Cr co-doped multiferroics compared to un-doped one. In addition, a prominent exchange anisotropy effect was observed from unsymmetrical M-H loops in all the samples at room temperature signifying promising practical applications.

SN Applied Sciences, 2019

Un-doped and Ni-doped lanthanum ferrite nanoparticles were synthesized by solid-state method. Ni ... more Un-doped and Ni-doped lanthanum ferrite nanoparticles were synthesized by solid-state method. Ni concentration-dependent structural, dielectric and optical properties of synthesized nanoparticles were investigated. X-ray diffraction patterns confirmed predominant single-phase orthorhombic crystal structure with space group Pbnm in all samples. Average crystallite size was found to vary from 19 to 21 nm with Ni concentration. The field emission scanning electron microscopy revealed nanocrystalline structure with homogenous distribution of particles. UV-Vis-NIR diffuse spectra captured at room temperature indicate that La 1−x Ni x FeO 3 is an indirect band gap material. The band gap varies from 1.70 to 1.85 eV with changing Ni concentration. Frequency-dependent dielectric constant, dielectric loss and ac conductivity were studied at room temperature. The dielectric constant was found to increase with increasing Ni content at high frequency. The loss factor resulted from domain wall resonance exhibited an identical dispersion behavior of dielectric constant. At high frequencies, the dielectric losses of orthoferrites were found to be low. This is attributed to the restricted motion of domain wall pointing its plausible practical applications in magnetically tunable filters and oscillators.

Results in Physics, 2019

Scientific endeavor for tailoring properties of functional materials offers a significant urge to... more Scientific endeavor for tailoring properties of functional materials offers a significant urge to material scientists. The driving force is to facilitate the current understanding that may create new pathway to alternative materials. BiFeO 3 is inherently multiferroic and its exploitation for applications in diversified fields are still required extensive investigations in different perspectives. In this context, we synthesized new Bi 0.85 Gd 0.15 Fe 1−x Cr x O 3 multiferroics prepared by wet chemical method using high purity metal salts. We mainly focused on the investigation of dielectric properties, ac electrical conductivity and complex electrical modulus of the synthesized materials. Crystallographic measurements confirmed its rhombohedral structure which gradually transforms towards orthorhombic structure with increasing Cr dopants. The grain size of the synthesized samples was found to vary from 68 to 22 nm depending on doping concentration. Dielectric properties of sintered samples were studied in the frequency range of 100 Hz-1 MHz. Frequency dependent dielectric constant has shown to display dielectric dispersion behavior. At higher frequencies (⩾10 5 Hz), due only to electronic and ionic polarizations the dielectric constant has shown to be independent of frequency. Complex impedance showed a semicircular arc due to the dominant grain boundary resistance and the electric modulus confirms the existence of electrical relaxation. The AC conductivity (σ AC) has shown to obey a power law. Obtained improved properties suggested that the synthesized Bi 0.85 Gd 0.15 Fe 1−x Cr x O 3 ceramic by partial substitution of A and B sites by + Gd 3 and + Cr 3 shows added advantage in application over the pure BiFeO 3 counterpart.

Conference Presentations by Mohammad Nazmul Hossain

IEEE 19th Electronics Packaging Technology Conference (EPTC), 2017

In this research, we synthesize and characterize gadolinium (Gd) and chromium (Cr) co-doped multi... more In this research, we synthesize and characterize gadolinium (Gd) and chromium (Cr) co-doped multiferroic bismuth ferrite (BiFeO3). Un-doped and doped BiFeO3 nanostructures were fabricated by chemical solution deposition (CSD) technique using precursor solutions of Bi, Fe, Gd and Cr based salts. X-ray diffraction (XRD) analysis confirmed crystalline BiFeO3 with a tendency towards phase transition from rhombohedral to orthorhombic structure due to co-doping. Crystallite size was found to vary from 68 to 25 nm with increasing Cr doping. Gd/Cr co-doped BiFeO3 also demonstrated a significant reduction in the optical band gap energy from 2.03 to 1.71 eV. Vibration Sample Magnetometer (VSM) results confirmed improved ferromagnetic properties of synthesized materials. A substantial enhancement of magnetization of 6 emu/gm was obtained for 5% Gd + 6% Cr doped multiferroic. Electric polarization measurements (P-E) displayed ferroelectric nature of the samples with a maximum remnant polarization of 0.23 µC/cm 2. Coexistence of improved ferromagnetic and ferroelectric orders has been shown in co-doped BFO. Magnetoelectrc measurements displayed an outstanding results with many folds increase in magnetoelectric coefficient, αME (6.5 V.cm-1 .Oe-1). The synthesized multiferroics may find potential application in memory devices.

Bull. Mater. Sci., 2019

The bandgap energy range of multiferroic bismuth ferrite is 2.2-2.7 eV, making it a promising can... more The bandgap energy range of multiferroic bismuth ferrite is 2.2-2.7 eV, making it a promising candidate for photovoltaic (PV) applications. But its efficiency is still very low (<2%). This report thus focusses on the application of bismuth ferrite (BFO) engineered with cobalt (Co) doping and on the tuning of its bandgap energy (E g). BiFeO 3 is a unique multiferroic material that simultaneously displays both ferromagnetic and ferroelectric properties at room temperature. Co doped with pure BiFeO 3 (BiFe (1−x) Co x O 3 ; x = 0, 0.05, 0.1 and 0.15) was synthesized by the sol-gel method and annealed at 600 • C. X-ray diffraction shows the well-arranged crystalline structure and peaks of pure and doped-BiFeO 3 nanoparticles. A suitable reduction of E g has been observed for Co-doped BiFeO 3 , which may be appropriate for the effective use in PV solar cells. Thermogravimetric analysis and differential scanning calorimetry were used to investigate the thermal decomposition character of the xerogel powder and the pattern of pure and doped BiFeO 3 phases. Field emission scanning electron microscopy images show the surface crystallography of pure and Co-doped BiFeO 3. Co-doped BiFeO 3 has considerably reduced the crystallite and particle size of the samples. We have calculated the E g of pure and doped BiFeO 3 using a UV-Vis-NIR spectrophotometer and the results show the important reduction of E g (1.60 eV) of the Co-doped samples, which may have potential applications in PV solar cells.

Journal of Electronic Materials, 2018

Multiferroic BiFeO 3 (BFO) with bandgap energy (E g ) between 2.2 eV to 2.7 eV is a potential can... more Multiferroic BiFeO 3 (BFO) with bandgap energy (E g ) between 2.2 eV to 2.7 eV is a potential candidate for photovoltaic (PV) application. However, the efficiency of BFO based PV solar cells is reportedly still too low (less than 2%) to be used for practical applications. Reducing E g of BFO without compromising the ferroelectric properties is a big challenge to the scientific community to obtain power conversion efficiencies beyond the maximum value of 26.6% reported in general for silicon based hetero-structure PV solar cells. In this context, samarium (Sm) and cobalt (Co) co-doped BFO (Bi 0:9 Sm 0:1 Fe 0:9 Co 0:1 O 3 ) nanoparticles were synthesized using the sol-gel method. X-ray diffractometry was employed to determine the structure of synthesized nanoparticles. A welldefined crystalline structure of co-doped BFO nanoparticles was confirmed. Field emission scanning electron microscopy was carried out to study grain morphology of synthesized nanoparticles. Sm and Co dopants have been shown to reduce grain size significantly from 68.3 nm to 18.5 nm. An UV-Vis-NIR spectrophotometer was used to measure diffuse reflectance to calculate E g . A significant reduction of E g down to 1.50 eV of co-doped BFO compared to undoped and or single doped counterpart has been manifested.

Transaction on electrical and electronic materials, 2019

Sol-gel as a chemical solution deposition technique is compatible with functional device fabricat... more Sol-gel as a chemical solution deposition technique is compatible with functional device fabrication technology. Single-phase bismuth ferrite (BiFeO 3) mutiferroic with its multi-functionality has extensively been studied for a variety of prospective novel device applications. However, the synthesis of BiFeO 3 is confronted with a challenge to produce pure state without any secondary phase. Scarcity of unified process parameters impede justification of best synthesis techniques. In this work, sol-gel methods with and without auto-combustion reactions were used to synthesize bismuth ferrite (BiFeO 3) nanoparticles. Different techniques UV-Vis-NIR spectroscopy, XRD, EDS, and SEM were used to investigate the effect of preparation routes on the crystal purity and properties of prepared samples. Synthesized nanoparticles were calcined at temperature between 400 and 800 • C and an optimal calcination temperature was found to be 600 • C. Band-gap was determined by UV-Vis-NIR spectroscopy and found to vary from 1.93 to 2.07 eV. X-ray diffraction (XRD) has confirmed single phase rhombohedral crystal structure with R3c symmetry. Avg crystallite size was found to be higher (40-68 nm) in auto-combustion reaction compared to that of 23-42 nm obtained in sol-gel method without auto-combustion reaction. The band-gap energy was found to reduce with decreasing crystallite size (above the critical size of 10 nm) following Brus's effective mass model. Induced strain was found to exhibit an inverse relation with crystallite size and displayed substantial reduction in auto-combustion reaction route. The microstructural features were investigated by field emission scanning electronic microscopy and avg particle size was shown to vary from 107 to 197 nm depending on adopted synthesis route. A low reaction temperature (70 • C-80 • C) without auto-combustion and calcination temperature at 600 • C were found to be optimal conditions for the preparation of low impurity un-doped bismuth ferrite nanaoparticles.

Materials Research Express, 2019

In this work, Gd and Cr co-doped Bi 0.95 Gd 0.05 Fe 1−x Cr x O 3 (x = 0-0.08) functional ceramics... more In this work, Gd and Cr co-doped Bi 0.95 Gd 0.05 Fe 1−x Cr x O 3 (x = 0-0.08) functional ceramics were synthesized by chemical solution deposition technique (CDS). The synthesized samples were annealed at different temperatures between 400-700 • C. The X-ray diffrac-tion (XRD) study revealed a partial phase evolution from R3c (rhombohedral) crystal structure to pna2 1 crystal structure (orthorhombic) with Gd doping which further enhanced with increasing Cr co-doping. XRD analysis has shown a significant reduction in crystallite size to 25 nm from 68 nm of un-doped BiFeO 3. Field Emission Scanning Electron Microscopy (FESEM) exhibited more uniform nanoparticles due to doping effects and the average size of particle was found to be higher compared to that obtained from XRD results. The magnetic measurement showed a significant improvement in ferromagnetic properties of the synthesized samples, in particular, an enhanced magnetization was obtained for 5 at.% Gd + 6 at.% Cr co-doped multiferroics compared to un-doped one. In addition, a prominent exchange anisotropy effect was observed from unsymmetrical M-H loops in all the samples at room temperature signifying promising practical applications.

SN Applied Sciences, 2019

Un-doped and Ni-doped lanthanum ferrite nanoparticles were synthesized by solid-state method. Ni ... more Un-doped and Ni-doped lanthanum ferrite nanoparticles were synthesized by solid-state method. Ni concentration-dependent structural, dielectric and optical properties of synthesized nanoparticles were investigated. X-ray diffraction patterns confirmed predominant single-phase orthorhombic crystal structure with space group Pbnm in all samples. Average crystallite size was found to vary from 19 to 21 nm with Ni concentration. The field emission scanning electron microscopy revealed nanocrystalline structure with homogenous distribution of particles. UV-Vis-NIR diffuse spectra captured at room temperature indicate that La 1−x Ni x FeO 3 is an indirect band gap material. The band gap varies from 1.70 to 1.85 eV with changing Ni concentration. Frequency-dependent dielectric constant, dielectric loss and ac conductivity were studied at room temperature. The dielectric constant was found to increase with increasing Ni content at high frequency. The loss factor resulted from domain wall resonance exhibited an identical dispersion behavior of dielectric constant. At high frequencies, the dielectric losses of orthoferrites were found to be low. This is attributed to the restricted motion of domain wall pointing its plausible practical applications in magnetically tunable filters and oscillators.

Results in Physics, 2019

Scientific endeavor for tailoring properties of functional materials offers a significant urge to... more Scientific endeavor for tailoring properties of functional materials offers a significant urge to material scientists. The driving force is to facilitate the current understanding that may create new pathway to alternative materials. BiFeO 3 is inherently multiferroic and its exploitation for applications in diversified fields are still required extensive investigations in different perspectives. In this context, we synthesized new Bi 0.85 Gd 0.15 Fe 1−x Cr x O 3 multiferroics prepared by wet chemical method using high purity metal salts. We mainly focused on the investigation of dielectric properties, ac electrical conductivity and complex electrical modulus of the synthesized materials. Crystallographic measurements confirmed its rhombohedral structure which gradually transforms towards orthorhombic structure with increasing Cr dopants. The grain size of the synthesized samples was found to vary from 68 to 22 nm depending on doping concentration. Dielectric properties of sintered samples were studied in the frequency range of 100 Hz-1 MHz. Frequency dependent dielectric constant has shown to display dielectric dispersion behavior. At higher frequencies (⩾10 5 Hz), due only to electronic and ionic polarizations the dielectric constant has shown to be independent of frequency. Complex impedance showed a semicircular arc due to the dominant grain boundary resistance and the electric modulus confirms the existence of electrical relaxation. The AC conductivity (σ AC) has shown to obey a power law. Obtained improved properties suggested that the synthesized Bi 0.85 Gd 0.15 Fe 1−x Cr x O 3 ceramic by partial substitution of A and B sites by + Gd 3 and + Cr 3 shows added advantage in application over the pure BiFeO 3 counterpart.

IEEE 19th Electronics Packaging Technology Conference (EPTC), 2017

In this research, we synthesize and characterize gadolinium (Gd) and chromium (Cr) co-doped multi... more In this research, we synthesize and characterize gadolinium (Gd) and chromium (Cr) co-doped multiferroic bismuth ferrite (BiFeO3). Un-doped and doped BiFeO3 nanostructures were fabricated by chemical solution deposition (CSD) technique using precursor solutions of Bi, Fe, Gd and Cr based salts. X-ray diffraction (XRD) analysis confirmed crystalline BiFeO3 with a tendency towards phase transition from rhombohedral to orthorhombic structure due to co-doping. Crystallite size was found to vary from 68 to 25 nm with increasing Cr doping. Gd/Cr co-doped BiFeO3 also demonstrated a significant reduction in the optical band gap energy from 2.03 to 1.71 eV. Vibration Sample Magnetometer (VSM) results confirmed improved ferromagnetic properties of synthesized materials. A substantial enhancement of magnetization of 6 emu/gm was obtained for 5% Gd + 6% Cr doped multiferroic. Electric polarization measurements (P-E) displayed ferroelectric nature of the samples with a maximum remnant polarization of 0.23 µC/cm 2. Coexistence of improved ferromagnetic and ferroelectric orders has been shown in co-doped BFO. Magnetoelectrc measurements displayed an outstanding results with many folds increase in magnetoelectric coefficient, αME (6.5 V.cm-1 .Oe-1). The synthesized multiferroics may find potential application in memory devices.