Spectral analysis and structure of Cu²⁺-doped cadmium bismuth borate glasses

237-244with excitations wavelength at 330 nm. The FTIR profile revealed that the glass has both BO3 and BO4 units. Due to presence New series of cadmium bismuth borate (CBBC) glasses have been developed by varying bismuth content in the chemical compositions of 20CdO.xBi2O3.(79.5-x)B2O3, where x = 15, 20, 25, 30 and 35 mol % Bi2O3, containing 0.5 mol% of Cu2+ ions. These glasses have been prepared by melt-quench technique (1150°C in air) for verifying there UV filtration performance. From the measurement of UV absorption spectra, both direct and indirect band gaps have been evaluated. Also different physical properties of the prepared glasses have also been studied. The refractive index of prepared glasses has been measured by using Brewster angle method. The amorphous nature of the glasses has been confirmed by X-ray diffraction. The spectroscopic properties of the glasses have been investigated using optical absorption spectra and fluorescence spectra. Optical transmission spectra of Cu2+ ions doped CBBC glasses have shown two peaks at 450 nm (2B1g → 2Eg) and 645 nm (2B1g → 2B2g). Emission spectra of (0.5 mol %) Cu2+: CBBC have revealed two emission transitions at 412 and 523 nm of both Bi203 and CdO, these glasses are found to be good moisture-resistant optical systems

Suppression of photo-darkening effect after exposure of light on Sb doped InSe

This present work focuses on the comparative study of InSe4 and Sb doped InSe4 films to investigate the effect of exposure time on the optical constants that are extracted from the absorbance and the transmittance data in the spectral range from 200 to 2500 nm. A tungsten lamp was used for exposure to study the influence of the illumination on the optical properties of the synthesized films. The crystallinity of InSe4 pure film was increased, whereas reverse effect was analyzed in doped film. The crystallite size of illuminated InSe4 and In0.9Se4Sb0.1 films was determined using Debye–Scherrer's formula. Tauc's plot was used to calculate the band gap of lit and un-illuminated films. The photo-darkening effect was observed in InSe4 film due to the reduction in the band gap value with exposure time. Photo-darkening was decreased in InSe4 film when it was doped with antimony (Sb). Wemple–Di-Domenico (WDD) model was used for examining the refractive index of the pure and doped films. Single oscillator energy (Eo) and dispersion energy (Ed) were estimated for synthesized film samples. The static refractive index and lattice dielectric constant for both pristine InSe4 and antimony-doped InSe4 films were calculated

Crystal structure refinement and magnetic properties of Bi0.8Ba0.2FeO3 substituted Na0.5Bi0.5TiO3 ceramics

In this study, Bi0.8Ba0.2FeO3 modified Na0.5Bi0.5TiO3 ceramics having composition (1 - x)(Na0.5Bi0.5TiO3) - x(Bi0.8Ba0.2FeO3) with 0 <= x <= 0.40 are fabricated by conventional solid state reaction technique. Rietveld analysis of X-ray diffraction pattern of the prepared ceramics revealed that all the samples crystallized into single phase with rhombohedral symmetry (R3c space group). Magnetic measurements were performed at room temperature up to a field of 6 kOe. The magnetic hysteresis loops for samples x <= 0.10 show linear magnetic field dependence of magnetization with narrow hysteresis loop, indicating the typical antiferromagnetic nature (AFM) with canted spins. For samples 0.20 <= x <= 0.40, an appreciable increase in the values of remnant magnetization and coercive field are observed. Thus, the addition of BBFO content gives rise to significant increase in magnetization

Crystal structure and magnetic properties of Bi0.8A0.2FeO3 (A = La, Ca, Sr, Ba) multiferroics using neutron diffraction and Mossbauer spectroscopy

Bi0.8A0.2FeO3 (A = La, Ca, Sr, Ba) multiferroics were studied using x-ray, neutron diffraction and magnetization techniques. All the samples crystallized in rhombohedral structure with space group R3c. The compounds exhibit antiferromagnetic (AFM) ordering at 300 K and no evidence of further structural or magnetic transition was observed on lowering of temperature below it. The magnetic structure of these substituted compounds are found to be collinear G-type AFM structure as against the non collinear incommensurate magnetic structure reported in the case of parent compound. The moments on Fe at 6 K are aligned along the a-axis in the case of Ca-doped sample. With increase in the ionic radii of dopant, the moments are found to be aligned in the ac plane and the angle of tilt away from the a-axis increases. The observed change in the magnetic structure with substitution is attributed to the intrinsic structural distortion as evidenced by the change in the bond angle (Fe-O-Fe) and bond distances (Bi-O, Fe-O). It has been found that heterovalent substitution A2+ results in the formation of oxygen vacancies in the parent lattices as the possibility of Fe4+ ruled out by Mössbauer spectra recorded at room temperature. Higher value of remnant magnetization (0.4187 emu/g) and coercivity (4.7554kOe) is observed in Bi0.8Ba0.2FeO3 sample in comparison to other substituted samples revealing a strong correlation between ionic radii and magnetization

Phase transformation in crystal and magnetic structure and improved dielectric and magnetic properties of Ho substituted BiFeO3multiferroics

The changes in crystal and magnetic structure of BiFeO3 produced by partial substitution of Bi ions by Ho ions has been studied with powder X-ray diffraction, neutron powder diffraction, dielectric and magnetization techniques. The present study demonstrates that Bi1-xHoxFeO3(x = 0.05, 0.10, 0.15, & 0.2) multiferroics shows change in crystal structure at x > 0.05. The sample with x = 0.05 exhibits rhombohedral structure (space group R3c), while the other three samples (x > 0.05) exhibit mixed phase with coexisting rhombohedral (R3c) and Orthorhombic (Pnma) structure. This change in the crystal structure is attributed to the distortion of FeO6 octahedra via substitution of Ho at phase boundaries. The magnetization studies indicate that doping of Ho in pristine BiFeO3 leads to enhancement in the ferromagnetic moment. We find that doping of Ho breaks the spin cycloid phase of BiFeO3 and creates a canted G-type antiferromagnetic structure in the hexagonal phase whereas the orthorhombic phase exhibits a collinear G-type AFM structure. The canting angle increases with increase in doping with Ho, leading to an enhancement in the ferromagnetic component in magnetization. Dielectric constant (ε′) and loss factor (tanδ) are measured in frequency range 1 kHz to 7 MHz and ε′ and tanδ show dispersion behaviour at low frequencies. The significant improvement in magnetization and dielectric properties is achieved by Ho substitution which in turn enhances the potential of BiFeO3 for multiferroics applications

Study of crystal structure, dielectric, magnetic and magnetoelecrtic properties of xCoFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 composites

Multiferroic composites of spinel ferrite and ferroelectric xCoFe(2)O(4) - (1-x)Na0.5Bi0.5TiO3 (with x = 0.10,0.30,0.50) were efficiently prepared by standard solid state reaction mechanism. X-ray diffractometer was used to analyze crystal structure of the prepared composites. The observed XRD patterns of the composites comprise peaks of both the phases i.e. ferrite and ferroelectric, with no sign of secondary peaks. Rietveld refinement of XRD data further confirms the coexistence of these two phases with cubic (Fd3m) and rhombohedral (R3c) symmetry corresponding to ferrite and ferroelectric phase respectively. The 3-dimensional overview of crystal structure of pure CoFe2O4 and Na0.5Bi0.5TiO3 and of composite 0.50CoFe(2)O(4) - 0.50Na(0.5)Bi(0.5)TiO(3) is generated by using refined parameters. The dielectric constant (epsilon') and dielectric loss (tan delta) values were recorded as a function of frequency ranging from 100 Hz to 7 MHz and at different temperatures. Both epsilon' and tan delta follow dispersion pattern at lower frequencies while show frequency independent behavior at higher frequencies. The magnetic evaluation carried by analyzing M-H hysteresis loop reveals the ferrimagnetic characteristics of these composites. The highest value of magnetic moment is 1.12 mu(B) observed for composite 0.50CoFe(2)O(4) - 0.50Na(0.5)Bi(0.5)TiO(3). Magnetoelectric (ME) voltage coefficient (alpha) was also demonstrated to observe the interaction between ferrite and ferroelectric phases. The highest value of alpha (72.72 mu V/Oe cm) is obtained for low ferrite composition 0.10CoFe(2)O(4) - 0.90Na(0.5)Bi(0.5)TiO(3), which suggests the dependence of magnetoelectric response on the resistivity of the composites

Crystal structure refinement, dielectric and magnetic properties of A-site and B-site co-substituted Bi0.90Nd0.10Fe1-xTixO3 (x=0.00, 0.02, 0.05 & 0.07) ceramics

Nd and Ti co-doped Bi0.90Nd0.10Fe1-xTixO3 (x = 0.00, 0.02, 0.05 & 0.07) ceramics were prepared via conventional solid state reaction method. The crystal structure was investigated by X-ray diffraction at room temperature. The XRD data was further studied by Rietveld refinement using Full prof suite which revealed the structural transformation from rhombohedral (R3c) into triclinic (P1) phase. Low values of R factors and chi(2) showed good agreement between experimental and refined intensities. The analysis of Raman spectra is consistent with the earlier reported data. Dielectric response of all the prepared samples was analyzed in the frequency range 100 Hz to 7 MHz at different temperatures. All the samples exhibited dispersion in dielectric constant values at lower frequencies and became nearly constant at higher frequencies. With Ti substitution, the dielectric constant became stable at higher frequencies due to suppression of oxygen vacancies. The temperature variation of dielectric constant and tans displayed sharp anomalies in the vicinity of Neel temperature. Impedance spectroscopy disclosed appearance of grain contributions in the prepared samples. Magnetic characterization was performed by using Vibrating sample magnetometer upto a field of 5 kOe at room temperature. The hysteresis loop exhibited inherent antiferromagnetism with a weak ferromagnetism. The maximum remnant magnetization (M-r) is observed for Bi0.90Nd0.10Fe0.95Ti0.05O3 is 3.15 memu/g and the corresponding value of coercive field is 130.65 Oe

Crystal structure, dielectric, magnetic and improved magnetoelectric properties of xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 composites

Magnetoelectric (ME) composites of NiFe2O4-(1-x)Na0.5Bi0.5TiO3 (NBT) with composition xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 (x = 0.20, 0.40, 0.60) were prepared successfully by solid state reaction method. The crystal structure analysis was carried by using x-ray diffractometer, field emission scanning electron microscope-energy dispersive analysis of x-rays (FESEM-EDX) and Fourier transform infrared spectroscopy (FTIR). The presence of two individual phases corresponding to ferrite and ferroelectric was confirmed by XRD analysis of composites. Rietveld refinement of XRD data further confirms the existence of both cubic (Fd3m) and rhombohedral (R3c) symmetries. FESEM micrographs and EDX spectra revealed the reduction in grain sizes with increase in ferrite content. FTIR spectra depict two prominent absorption bands around 413 cm(-1) and 618 cm(-1). Dielectric response of these samples was recorded at frequency range 100 Hz-7 MHz for different temperature. Dielectric constant (epsilon') and dielectric loss (tan delta) values found higher at low frequencies, decrease with increase in frequencies and become independent at higher frequencies. epsilon' and tan delta both enhance with rising temperature and become more stable at higher frequencies. Complex impedance spectroscopy (CIS) investigation was used to understand dielectric relaxation and conduction mechanism in composites. Cole-Cole plots for all samples depict two semicircles and the centre of semicircles is depressed below real axis with temperature. Activation energy rises with increase in ferrite content in composites. Magnetic evaluation of the samples discloses the soft magnetic nature of these composites. The maximum value of saturation magnetization (M-s = 22.82 emu g(-1)) and magnetic moment per formula unit (eta = 0.92 mu(B)) is observed for composition having higher NFO content. The highest ME response, alpha similar to 1122 mu V/cmOe is observed for the composite 0.60NiFe(2)O(4)-0.40Na(0.5)Bi(0.5)TiO(3)

Crystal structure, dielectric, magnetic and magnetoelectric properties of xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 composites

Magnetoelectric (ME) composites xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 (x = 0.10,0.30,0.50) were synthesized by conventional solid state reaction method. Crystal structure and microstructural characteristics of these composites were investigated by XRD and SEM respectively. Rietveld analysis of XRD pattern confirms the coexistence of cubic (Fd3m) and rhombohedral (R3c) symmetry simultaneously in these composites. The microstructural evaluation discloses the effect of constituent phases on the average grain size of a composite. The dielectric constant (epsilon') and dielectric loss (tan delta) were examined as a function of frequency within range (100 Hz to 7 MHz) and at different temperatures. The magnetic behavior of composites was determined by MH hysteresis loop which reveals their soft magnetic behavior. ME voltage coefficient was determined to study the coupling between ferrite and ferroelectric phases. The maximum value of ME coefficient alpha approximate to 223 mu V/cmOe was observed for 0.10NFO-0.90NBT sample