Peng Song; Zhipeng Pei; Heng Wu; Yao Lu; Weiren Xia; Xinhua Zhu
Abstract
Double-perovskite structured multiferroic Bi2FeMnO6 (BFMO) ceramics synthesized via solid-state reaction route at 880 o C for 3 h, crystallized in a distorted rhombohedral structure with R3c space group. Their lattice parameters in the hexagonal system were determined to be a = 5.571 Å and c = ...
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Double-perovskite structured multiferroic Bi2FeMnO6 (BFMO) ceramics synthesized via solid-state reaction route at 880 o C for 3 h, crystallized in a distorted rhombohedral structure with R3c space group. Their lattice parameters in the hexagonal system were determined to be a = 5.571 Å and c = 13.191 Å. SEM images show that the BFMO ceramic grains exhibit spherical morphology with an average size of 6.70 mm. Their atomic ratio of Bi:Fe:Mn was determined to be 2.07:1.02:1.00, close to the nominal value of 2:1:1. Raman spectra have verified the vibrational frequencies in the BFMO ceramics, and only 11 Raman active modes are observed. The less observed Raman modes in the BFMO ceramics compared with the theoretical group analyses, can be ascribed to the small correlation field splitting of the ceramic samples due to their polycrystalline nature. BFMO ceramics exhibit almost frequency-independent dielectric behavior in a frequency range of 500 - 10 6 Hz at room temperature. Their dielectric constant and dielectric loss were measured to be 700 and 0.03 at 10 6 Hz, respectively. The piezoelectric moduli d33 of the poled BFMO ceramics was measured to be 56 pC/N, which is two times larger than that reported for BiFeO3 thin film (d33 ≅ 25 pC/N). Copyright © VBRI Press.
Pravin M. Tirmali; Sagar M. Mane; Snehal L. Kadam; Shrinivas B. Kulkarni
Abstract
The double perovskite materials show the magnetic semiconductor, magneto-optic and magneto-capacitance like interesting properties. It is predicted that the B-site substitution in this system may results in interesting properties. La2Ni1-xFexMnO6 thin films are deposited on Pt/Ti/ Si(100) substrate ...
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The double perovskite materials show the magnetic semiconductor, magneto-optic and magneto-capacitance like interesting properties. It is predicted that the B-site substitution in this system may results in interesting properties. La2Ni1-xFexMnO6 thin films are deposited on Pt/Ti/ Si(100) substrate by Pulse Laser Deposition (PLD) technique. The films were uniform, fine grain and stoichiometric deposited at very low O2 pressure. The XRD of La2Ni1-xFexMnO6 thin films exhibits rhombohedral (R-3) phase. The peak broadening appears in Raman spectra at antistretching (518 cm -1 ) and stretching (656 cm -1 ) modes with presence of overtone modes at 1308 cm -1 in La2Ni1-xFexMnO6 thin film samples. XPS analysis reveals the presence of La 3+ , NiO, Ni 3+ , Fe 3+ , Mn 3+ and oxygen vacancies in samples. The Ni 3+ and Mn 3+ antiferromagnetic coupling is responsible for decrease in saturation magnetization Ms from 4.78 to 2.74 µB/f.u as Fe substitution increases from 0.1 to 0.3 at 5K. The increase in grain size, peak broadening and decrease in magnetization of La2Ni1-xFexMnO6thin film samples suggest presence of antisite defects and antisite phase boundary. The present work will helpful to study the effect of B site substitution on La2NiMnO6 thin films structural, electronic and magnetic properties in order to make it suitable candidate for potential applications.
Preetam Singh; K. M. K. Srivatsa; Sourav Das
Abstract
Polycrystalline Si (Poly-Si) film with highly crystalline nature, and having most of the grains in the range of 50-100 µm has been grown over biaxially textured Ni-W substrate by Hot-wire chemical vapor deposition technique, using a single buffer layer of CeO2 thin film. This result has been achieved ...
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Polycrystalline Si (Poly-Si) film with highly crystalline nature, and having most of the grains in the range of 50-100 µm has been grown over biaxially textured Ni-W substrate by Hot-wire chemical vapor deposition technique, using a single buffer layer of CeO2 thin film. This result has been achieved for the SiH4 source gas diluted to 95% with added H2 gas, and for the substrate temperature of 840±10oC and a deposition pressure of 40 mTorr. XRD analysis shows that the Poly-Si films have grown with (111) and (200) orientations. Raman studies reveal that a crystalline volume fraction of 95.3% has been achieved. The imaginary part of pseudo dielectric function, <ε2>, as extracted from ellipsometric data, shows two prominent shoulders at energy positions 3.4 eV and 4.2 eV corresponding to the optical absorption of crystalline Si, indicating a high crystallinity of the Poly-Si film. SEM micrograph shows that the grown Poly-Si film is following the morphology and grain size as that of biaxially textured Ni-W substrate. SIMS analysis of the total multilayer structure shows a formation of very sharp interfaces, with no diffusion between Si and Ni, indicating that a single buffer layer of CeO2 is sufficient to avoid the formation of nickel silicide while growing Si over Ni substrate. Thus, these results are very encouraging for the fabrication of Poly-Si film based solar cells with increased efficiency by minimizing the undesired recombination of charge carriers at grain boundaries.
Nikita H. Patel; M.P. Deshpande; Sandip V. Bhatt; Kamakshi R. Patel; S. H. Chaki
Abstract
Undoped and Mn doped CdS nanoparticles with varying Mn concentration of 10,15 and 20 mol % have been prepared by chemical co-precipitation method with polyvinylpyrrolidone (PVP) as capping agent at room temperature. EDAX has shown that no foreign impurities are present in the synthesized nanoparticles ...
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Undoped and Mn doped CdS nanoparticles with varying Mn concentration of 10,15 and 20 mol % have been prepared by chemical co-precipitation method with polyvinylpyrrolidone (PVP) as capping agent at room temperature. EDAX has shown that no foreign impurities are present in the synthesized nanoparticles and X-ray diffraction (XRD) revealed that undoped and Mn doped CdS nanoparticles possess cubic phase with crystallite size ranging from 4-6 nm. Transmission electron microscopy (TEM) images indicated that nanoparticle sizes are between 2-6 nm and exhibits polycrystalline nature as seen from selected area electron diffraction (SAED) pattern. Raman spectra of undoped and Mn-doped CdS nanoparticles have shown 1LO and 2LO phonon modes and their intensity ratio decreases as Mn concentration increases. Magnetic susceptibility clearly pointed out that undoped CdS behaves as diamagnetic whereas Mn doped CdS as paramagnetic and varies nonlinearly with Mn concentration in CdS. Rapid increase in magnetization below 50 K temperature is observed in M-T curves which can be assigned to Mn ions isolated in CdS crystal field or extrinsic defects. The M-H curve at 5 K and 300 K for 20% Mn doped CdS nanoparticles at different magnetic fields showed no hystersis. In near future Mn doped CdS nanoparticles can be used for application in dilute magnetic semiconductor and fabrication of solar cells. The result and discussion drawn from this work are elaborated in detail in the paper.
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