Structural, vibrational, optical, magnetic and dielectric properties of Bi1−xBaxFeO3 nanoparticles

Layered PVB/Ba3Co2Fe24O41/Ti3C2 Mxene composite: Enhanced electromagnetic wave absorption properties with high impedance match in a wide frequency range

Effect of lattice strain on structural and magnetic properties of Ca substituted barium hexaferrite

Effect of Ba–Nb co-doping on the structural, dielectric, magnetic and ferroelectric properties of BiFeO3 nanoparticles

Polycrystalline M-type hexagonal Barium ferrite (BaFe12O19) was prepared by the solid state reaction method. The single phase and well grain growth of micrometer range was confirmed by XRD pattern and SEM image respectively. The presence of Fe2+ and Fe3+ states were verified by XPS study. In this report, the electric transport properties of BaFe12O19 (BaM) was systematically investigated and analyzed in the frequency range of 100 Hz to 1 MHz and temperature range of 30–200 °C. The relaxation behaviors were examined by considering both impedance and modulus formalism, to differentiate intrinsic (grain) and extrinsic (grain boundary and electrode polarization) conduction process. The co-contribution effect of grain and grain boundary was verified which appeared as a single relaxation process in the chosen frequency and temperature range. However, the sample experienced the early (even at room temperature) arrival of surface conduction which dominates over grain boundary with increasing of temperature.

Electric transport properties study of bulk BaFe12O19 by complex impedance spectroscopy

Bi0.8Sr0.2Fe1−xNbxO3 (x = 0.0, 0.05, and 0.10) multiferroics were prepared by solid state reaction method. X-ray diffraction and Rietveld analysis show that crystal structure is rhombohedral for x = 0.0, 0.05 samples and triclinic for x = 0.10 sample. These samples showed dispersion in dielectric constant (έ) and dielectric loss (tan δ) values at lower frequencies. For x = 0.05 sample, both έ and tan δ are lower than for Bi0.8Sr0.2FeO3 sample indicating its high resistivity. For x = 0.10 sample, the value of έ is enhanced which may be due to formation of stronger dipoles in triclinic structure. Temperature dependence of frequency exponent “s” of power law suggests that correlated barrier hopping (CBH) model is applicable at lower temperatures and quantum mechanical tunneling model is appropriate at higher temperatures for describing the conduction mechanism in x = 0.0 and x = 0.05 samples; while in x = 0.10 sample, CBH model is appropriate in studied temperature range. Significant enhancement observed in magnetization for x = 0.10 sample is due to the structural phase transition from rhombohedral to triclinic caused by Nb substitution. For this sample, values of remnant magnetization (Mr) and coercive field (Hc) are 0.155 emu/g and 2.695 kOe, respectively.

Phase transformation, dielectric and magnetic properties of Nb doped Bi0.8Sr0.2FeO3 multiferroics

M-type hexaferrites with compositions BaFe12O19 (BFO), SrFe12O19 (SFO), Ba0.5Sr0.5Fe12O19 (BSFO), and Ba0.5Pb0.5Fe12O19 (BPFO) were synthesized by commercial solid state reaction method. The Rietveld refinement of x-ray powder diffraction revealed a single hexagonal phase with space group P63/mmc for BFO, SFO, and BSFO samples, whereas BPFO sample contains hematite (α-Fe2O3) phase with space group R3c along with the M-type main phase. All the samples show dispersion in dielectric constant (ɛ′) and dielectric loss (tan δ) values with frequency. The values of ɛ′ and tan δ increase with increase in temperature due to increase in the number of charge carriers and their mobilities, which are thermally activated. The reciprocal temperature dependence of conductivity (σac) and the most probable relaxation time (τM″) satisfies the Arrhenius relation. A perfect overlapping of the normalized plots of modulus isotherms on a single “super curve” for all the studied temperatures reveals a temperature independence of dynamic processes involved in conduction and for relaxation. Further, the complex plots of M* (M″ vs M′) indicate that dc conductivity dominates in the region below the M″max point. Above M″max, the variations follow Jonscher power law (σ = Aωs) implying that ac conductivity is dominating in this region. Among the prepared samples, SFO hexaferrite has lowest values of σac, ɛ′, and tan δ making it suitable for use in microwave devices.

Structure refinement and dielectric relaxation of M-type Ba, Sr, Ba-Sr, and Ba-Pb hexaferrites

Lithium lead silicate glasses with composition 30Li2O⋅(70‐x)PbO⋅xSiO2 (where, x = 10, 20, 30, 40, 50 mol %) (LPS glasses) were prepared by normal melt quench technique at 1373 K for half an hour in air to understand their structure. Compositional dependence of density, molar volume and glass transition temperature of these glasses indicates more compactness of the glass structure with increasing SiO2 content. Fourier transform infrared (FTIR) spectroscopic data obtained for these glasses was used to investigate the changes induced in the local structure of samples as the ratio between PbO and SiO2 content changes from 6.0 to 0.4. The observed absorption band around 450–510 cm−1 in IR spectra of these glasses indicates the presence of network forming PbO4 tetrahedral units in glass structure. The increase in intensity with increasing SiO2 content (upto x = 30 mol %) suggests superposition of Pb‐O and Si‐O bond vibrations in absorption band around 450–510 cm−1. The values of optical basicity in these glasse...

Infrared Spectroscopic Study For Structural Investigation Of Lithium Lead Silicate Glasses

Barium bismuth silicate glasses (BBS glasses) with composition were prepared by normal melt quench technique. The dispersive conductivity and dielectric losses in these glasses were investigated by impedance spectroscopy. The analyses of ac conductivity spectra show a crossover from ion hopping conductivity to nearly constant loss (NCL) contribution in all the glasses. The variations in dielectric constant e*(ω) = e′(ω)‐ie″(ω) with frequency and temperature indicate an increase in electrode polarization, which reduces the dipolar relaxation effects in these glasses. The increased concentration of BaO in the glass composition reduces the dielectric losses in the present glasses.

Monica

Papers

Phase transformation, dielectric and magnetic properties of Nb doped Bi0.8Sr0.2FeO3 multiferroics

Structure refinement and dielectric relaxation of M-type Ba, Sr, Ba-Sr, and Ba-Pb hexaferrites

Infrared Spectroscopic Study For Structural Investigation Of Lithium Lead Silicate Glasses

Investigation Of Dispersive Conductivity And Dielectric Losses In Barium Bismuth Silicate Glasses