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In the present attempt, order-to-disorder transition of oxygen vacancies and their correlation with ion transport mechanism in moderately (at.15%) and heavily (at. 30%) doped (Gd and Sm) ceria systems are explored by using a high-temperature X-ray diffraction (HT-XRD) and Raman and dielectrics spectroscopy techniques. Oxygen vacancies disordering is integrated with polarization phenomenon. The density of disordered oxygen vacancies and conducting ions is revealed by the imaginary part of electric modulus (M”). Relaxations of conducting ions are confirmed by M” as a function of frequency at various temperatures, and peak height M” curve is used to quantify the density of disorder states. HT-XRD study exhibits detectable mismatch in lattice parameter during expansion and contraction at particular temperature. The mismatch parameter is correlated to kinetic process induced in the samples caused by long-range disordering of oxygen vacancies. HT-Raman spectra confirm temperature-dependent disordering of oxygen vacancies. The energy of disordering of oxygen vacancies at grain and grain boundaries region is calculated from the slope of the log (fmax) versus 1000/T plots, where fmax is the frequency associated with M”max. Disordering energy at the grain boundary is more than grain in almost all systems. The temperature correspond to the order–disorder transition of oxygen vacancies is closely associated with oxy-ion conductivity. Arrhenius plot of conductivity depicts the kink in the slope of the conductivity curves for all ceria systems for the temperature ranges from 400 to 500 °C. The activation energy of conductivity in the temperature region of ordered oxygen vacancies is more than disordered oxygen vacancies. Conductivity maxima are associated with the density of disordered oxygen vacancies.

Understanding the concept of light–matter interaction in organic–inorganic nanostructures such as graphene and metal-halide perovskites has been explored to realize photonic and optoelectronic devi...

The double perovskite nanostructures were prepared by using hydrothermal route to obtain single-phase rhombohedral structure. The flexible magneto-dielectric nanocomposite films with double perovskite La2NiMnO6 (LNMO) nanostructures and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer were fabricated by solution casting method. The structural, thermal, and dielectric properties of the developed double perovskite nanostructures and their combination with (PVDF-HFP) as nanocomposite films were investigated. The fabricated nanocomposite films demonstrated an improvement in the crystalline phase with the increase in the loading of La2NiMnO6 (0–40 wt%). The nanocomposite film with 30 wt% of LNMO exhibited higher dielectric permittivity (> 40) alongside with a dielectric loss of as low as 0.6 at room temperature and thereafter it reached percolation threshold. The dielectric studies also revealed an efficient charge separation and a strong interfacial polarization at the interfaces by facilitating the charge accumulation in the nanocomposites than that of the pure polymer film. The thermally activated relaxation behavior in the films followed the Arrhenius law and the obtained activation energies were found to be ~ 1.12 eV.

In the present attempt, a Dy, W co-doped La2Mo2O9 (LMX) system is explored to understand the order–disorder phase transition, dynamical disorder state and their influence on the oxy-ion diffusion mechanism. The X-ray diffraction study confirms the co-dopant induced suppression of the order–disorder phase transition temperature of LMX. The oxygen ion diffusion in the LMX matrix is through intrinsic oxygen vacancies. Disorder oxygen vacancies enhance the degree of freedom of oxy-ion diffusion; these are related to the dynamical disorder states in LMX. These disorder states are demonstrated by high temperature Raman spectra. Dynamical disordering of oxygen vacancies in co-doped LMX systems is revealed by studying the rate of change of intensity of the Mo–O bond vibration as a function of temperature; non-uniformity in the rate of change of intensity is correlated to dynamical disorder. The dielectric relaxation studied by using dielectric loss spectra reveals a single relaxation peak for the pure-LMX system, while two dielectric relaxation peaks are revealed for doped LMX systems. Oxygen vacancy reorientation associated with dielectric relaxation is correlated to the diffusion process between O(1) → O(2) and O(1) → O(3) oxygen ion-vacancy exchange sites in doped LMX systems, while it is O(1) through orderly arranged oxygen vacancies in the pure LMX system. To ascertain the relaxation dynamics of the bulk system, electric modulus formalism is helpful, M′′ data are fit by the Bergman function represented by the Kohlrausch–Williams–Watts (KWW) formula and non-Debye type relaxation is revealed for all systems. The activation energy of oxy-ion diffusion is reduced by a co-doping effect. Ionic conductivity extracted from complex impedance spectra indicates that oxy-ion conductivity in a co-doped LMX system is improved almost one order as compared to the pure system. The study reveals that a co-doped LMX system has the potential to be used as electrolytes for intermediate temperature solid oxide fuel cells (400–700 °C, IT-SOFCs).

Efficient, host-sensitized, visible and near-infrared emitting phosphors NaY(MoO4)2, doped with Ln3+ (Ln = Er and Ho) were synthesized by a conventional solid state reaction and characterized with X-ray diffraction, photoluminescence emission and excitation spectra. Rietveld refinement was performed to investigate the phase purity of the NaY(MoO4)2 samples. Sensitization of Ln3+ (Ln = Er and Ho) from the host with different doping concentrations of Ln3+ were investigated. Under excitation at 310 nm, the phosphor gives intense and characteristic emission of Er3+ and Ho3+ in both the visible and NIR region due to sensitization by MoO42− group. In the excitation spectra there is a broad band ranging from 250 to 380 nm which is associated with the O2−-Mo6+ charge transfer transition in the MoO42− group. An efficient energy transfer from MoO42− to Er3+ and MoO42− to Ho3+ is observed. The interesting luminescence properties highlight the significance of Er3+/Ho3+ doped NaY(MoO4)2 phosphor for their use in optical and photonic devices.

In the present study, we have developed a convenient co-precipitation route using water as a solvent for stabilization of pure La2NiMnO6 (LNMO) nanoparticles. The structural stability of LNMO nanoparticles is achieved at lower temperature (∼600 °C) in relatively short time (6.5 h). X-ray diffraction data revealed a single-phase monoclinic structure with P21/n space group. Distortion in the unit cell is responsible for an overall decrease in the cell volume of LNMO nanoparticles as compared to that of its bulk counterpart. The band gap estimated for LNMO nanoparticles is 2.61 eV which is larger than that of the corresponding bulk system (1.4 eV). Transmission electron microscopy confirms that mean particle size is in the nanoscale range and has spherical morphology. A large decrease is observed in the Curie temperature for LNMO nanoparticles which is correlated with the structural distortion. Magnetic studies indicate that there is very little antiferromagnetic antisite disorder.

Lead free BaTiO3-La2NiMnO6 (BTO-LNMO) composite sample was prepared via solid-state sintering route. Structural studies based on X-ray diffraction (XRD) patterns indicate BTO and LNMO each retain their respective structure in composite form. Raman spectra of composite inferred no structural modulation after mixing of individual phases of BTO and LNMO. The change in microstructure is observed for composite due to the difference in thermal expansion coefficient as well as the different rate of grain growth of BTO and LNMO phases. BTO-LNMO composite sample is found to be ferromagnetic with non saturation of magnetic moments. Temperature-dependent zero-field cooled (ZFC) and field cooled (FC) curves show large irreversibility (94%) for composite than the pure LNMO phase. The magnetic Curie temperature (Tc) of the composite was observed near room temperature. The dielectric and ferroelectric features of BTO is well maintained in composite at room temperature. This study is an attempt to bring in the multiferroicity (magnetic and ferroelectric order simultaneously) in the proximity of room temperature by incorporating the small percentage of magnetic phase (LNMO) in the ferroelectric (BTO) matrix.

The ferromagnetic and ferroelectric laminated structure has been utilized to study the magnetoelectric (ME) effect, which holds great potential to fabricate micro-electro-mechanical devices with a high figure of merit. Designed a laminated heterostructure using ribbons of Metglas (Fe–Co–Si–B alloy) having high magnetic permeability and lead-free piezoelectric composites of 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO3 (NBT-BT) to generate the significant magnitude of direct ME voltage. The displacement-voltage measurements of NBT-BT yield a high response showing the nature of the piezoelectricity effect. The strength of ME coupling is determined from the ME voltage coefficient (αME), ME measurements have been carried out in the range of 0–6 kHz frequencies. The magnitude of the direct ME effect was found about 45–50 mV/Oe.cm over a low magnetic field of less than ±8 kOe. The real-time ME effect produced nearly 274.5 and 280.2 mV of ME voltages for the applied field of 200 and 300 Oe, respectively. It shows that the trilayer composite structure may be used as weak magnetic field sensors and energy harvesters.

Present work demonstrates our attempts of enhancement of room temperature magnetic stability and dielectric ordering of BiFeO3 via perovskite-spinel composite approach. We selected CoFe2O4 spinel phase for the study. (1-x)BiFeO3(BFO)-xCoFe2O4(CFO) composites with compositions (x = 0, 20, 30, 40 wt%) were developed. Structure of the composite are ensured by Rietveld refinement of XRD patterns; which reveal rhombohedral (space group:R3c) symmetry for BFO and inverse spinel cubic (space group: Fd 3 ¯ m) symmetry for CFO. Microstructural backscattered electron image of sintered composites shows well distribution of CFO in BFO matrix with interaction of BFO and CFO phase at the interface. Remanent magnetization observed for composites is found to be 3 times higher than estimated value by using Vegard's law. Higher magnetic stability achieved in composites. Room temperature dielectric properties of BFO-CFO composites revealed higher dielectric constant with low loss. The enhancement in magnetic stability and dielectric ordering of composites might be useful in miniaturizing antenna system and electromagnetic shielding materials.

Nanostructures of complex oxides [BiFexMn2−xO5 (x = 0, 1, 2)] have been designed to study their structural, optical and magnetic behaviour. X-ray diffraction data (XRD) revealed orthorhombic phase with Pbam space group. Noticeable expansion in unit cell parameters has been found from BiMn2O5 (x = 0) to BiFe2O4.5 (x = 2). The observed structural changes via tuning of B-site (x = 0–2) played an important role in overall magnetic properties. Transmission electron microscopic images confirm that the average particle size of all the materials are in nano domain range with different morphologies. From optical studies, it has been found that the observed energy band gap values are strongly related to 3d electron numbers. These values appear to be larger than that reported for bulk. Isothermal magnetization plots (at 5 K) show increase in coercivity (Hc) from x = 0 to x = 2. Temperature dependent magnetization studies implied anti-ferromagnetic interactions for BiMn2O5, frustrated magnet for BiFeMnO5 and ferromagnetic behaviour for BiFe2O4.5. Ferromagnetic state of nanostructured BiFe2O4.5 is in contrast with its bulk counterparts.

In the present attempt, we report modified features of structural, dielectric, magnetic and ferroelectric behaviour of BiFeO 3 (BFO) by perovskite-spinel composite approach. ZnFe 2 O 4 (ZFO) is used as spinel phase. The structural measurement of composite show anisotropically compression in the BiFeO 3 lattice with ZFO compositions and stimulates the variation in bond length, bond angle, tilting angle, electron density and resultant polarization. This affects on magnetic and dielectric behaviour of BFO. Room temperature magnetic measurement revealed enhancement of magnetization of BFO in composite, attributed to spin restructuring due to change in magnetic anisotropy, exchange energy and stress energy at interface with ZFO composition. There is around 7 times enhancement in magnetization as compared to pure BFO phase. Dielectric profile of composites shows decrease in dielectric constant as well as dielectric loss as compared to single phase BFO. P-E loop exhibits leaky ferroelectric behaviour of composite system with drop down in leakage current by 2 order of magnitude than pure BFO phase. Magnetic contributions of individual phases in composite are determined by Vegard Law while dielectric contributions are modelled by Maxwell-Garnett (MG) equation. The present work demonstrates that BFO-ZFO: perovskite-spinel composite approach to modify magnetic, dielectric and ferroelectric behaviour and to facilitate BFO as room temperature multiferroic system.

Polycrystalline Sm3(Fe1−xAlx)5O12 (x =0, 0.1, 0.2, 0.3, 0.4) samples were prepared in single phase form. Rietveld analysis of X-ray diffraction patterns shows that samples crystallize in cubic structure (space group: $$Ia\overline{3} d$$ ) with a systematic decrease in lattice constant with Al doping. Magnetization measurements show that all these samples exhibit ferrimagnetic transition whose transition temperature (Tc) decreases from 562 K for x =0 to 350 K for x =0.4 due to the dilution of Fe3+–O–Fe3+ networks. In addition to that they undergo spin reorientation transition at TSR~ 70 K with considerable magnetic irreversibility below TSR. Interestingly the x =0.4 sample undergoes magnetic compensation at 26 K. Improvement of frequency response of dielectric constant ( $$\varepsilon^{\prime}$$ ) and loss tangent (tan $$\delta$$ ) is observed upon Al doping in a wide frequency range of 102–109 Hz.

In the present work, low pressure synthesis of BiMnO3 (BMO) nanoparticles (NPs) by hydrothermal method is reported. Temperature-driven structural transitions of BMO are studied by X-ray diffraction (XRD) and exhibited that as-synthesized BMO is stabilized in monoclinic phase with C2 symmetry. However at 473 K, XRD pattern reveals abrupt changes in the intensity of peaks and lattice parameters. The origin of temperature-dependent symmetry transition is understood by sphenoid to prismatic transition by curtail of crystalline growth along (110) direction. The monoclinic structure with C2/c symmetry is found till 723 K. However, at 773 K and above XRD patterns are matched with Bi2Mn4O10 and Bi2O3 phases. The temperature profile of magnetic study exhibits antiferromagnetic behaviour. M–H curve provides evidence of weak ferromagnetism. The present results suggest that NPs of BMO exhibit coexistence of antiferromagnetism–ferromagnetism, however bulk BMO is ferromagnetic. X-ray photoelectron spectroscopy study reveals the presence of Mn in both +3 and +4 states in BMO NPs. Superexchange interaction between Mn4+–O–Mn3+ induces AFM along with weak FM in BMO. This study signifies the low pressure synthesis of BMO and its anomalous structural and magnetic behaviour.

Luminescence down-conversion is an excellent spectral conversion process to minimize the spectral mismatch between the incident solar radiation and the spectral response of a semiconductor (crystalline silicon (c-Si)) solar cells. For this purpose, we are proposing a novel near-infrared emitting Sr5(PO4)3Cl:Eu2+, Nd3+ phosphor prepared by solid state reaction. The prepared material has been characterized by using XRD, photoluminescence excitation (PLE), photoluminescence (PL) and fluorescence decay spectral measurements. The material shows a strong broadband excitation of Eu2+ in the wavelength range of 200–450 nm along with an intense Nd3+ NIR emission around 1000 nm which is favorable for solar spectrum modification. The PLE and PL spectra suggest that sensitization of Nd3+ NIR emission is possible via a strong 4f→5d transition of Eu2+ in Sr5(PO4)3Cl phosphor. We have also investigated the energy-transfer (ET) phenomenon occurring between the sensitizer (Eu2+) and activator (Nd3+) using fluorescence decay measurements. The results suggest that Eu2+-Nd3+ co-doped Sr5(PO4)3Cl phosphor with broad excitation band in the UV-blue region and intense NIR emission around 1 μm is aptly suitable as luminescent down converter useful crystalline silicon (c-Si) solar cells.

In the present study, we have developed a process to stabilize La2NiMnO6 (LNMO) nanorods via hydrothermal process using cetyl trimethylammonium bromide as a capping agent. One dimensional morphology (nanorods) of LNMO leads to MnO6 octahedral expansion that contributed to the overall expansion in LNMO unit cell. Large shape anisotropy of nanorods carries structural (unit cell) modification in the form of horizontal and vertical tilt of NiO6 and MnO6 octahedra along the c axis. Large saturation magnetization Ms is observed for LNMO nanorods as compared to that of their bulk and nanoparticles. X-ray photoelectron spectroscopy (XPS) analysis confirmed the large Ms values observed for nanorods could be attributed to mixed valence states of magnetic ions at B-site (Mn3+, Mn4+, Ni2+, Ni3+). The optical studies of LNMO nanorods shows that the observed band gap (Eg: 1.9 eV) is considerably larger than band gap reported for bulk LMNO (Eg: 1.2–1.4 eV). The enhanced saturation magnetization of nanorods is consistent with a structurally ordered single phase material with very few antisite defects.

Highlights: • Hydrothermal synthesis of TbMnO{sub 3} nanoplate. • Morphology induced defects detected by Raman spectroscopy. • Magnetic and dielectric anomalies confirmed multiferroic behavior is retained in TbMnO{sub 3} nanoplates. - Abstract: In the present study, hydrothermally prepared TbMnO{sub 3} in plates-like morphology at nanoscale are investigated in multiferroic view point. X-ray diffraction study confirms the orthorhombic phase of as-synthesized TbMnO{sub 3}. Microstructural features studied by Scanning Electron Microscopy and Transmission Electron Microscopy show the plates-like morphology of as-synthesized TbMnO{sub 3} at nanoscale. Local distortions investigated by FT-Raman exhibits redshift in T mode by about 20 cm{sup −1} as compared to that of the single crystal. The redshift in T mode is mainly due to defect by tilting of octahedra and respective changes in bond angle of Mn–O(1)–Mn. This is assigned to the size-morphology induced defects. The temperature dependent zero-field-cooled and field-cooled magnetization are measured at H = 50 Oe and in the temperature range 2–300 K. The anomalies in magnetization are obtained at 8 and 42 K. Bifurcation of the ZFC and FC curves are observed very close to magnetic transition temperature 42 K. The 42 K anomaly is related to the sine wave ordering of Mn{sup 3+} moment;more » and 8 K anomaly is associated with magnetic ordering of the Tb{sup 3+}-sublattice propagation vector. The anomalies in the electric properties, ϵ′ (T), tan δ (T), which are noticed within the 28 K range, coincide with the temperature of incommensurate–commensurate (or lock-in) magnetic transition of TbMnO{sub 3.} This study confirms that multiferroic behavior is retained in TbMnO{sub 3} nanoplates.« less

LaFeO3 (LFO) nanoparticles were prepared by microwave-assisted sol–gel combustion method with an aid of glycine as fuel. The calcined LFO sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), EDAX and UV–Vis absorption spectroscopy. Single-phase orthorhombic structure is confirmed by XRD, and data is well fitted using Rietveld refinement by Full-Prof suite. FTIR study displays vibrational modes related to orthoferrites perovskite LaFeO3. SEM images depict fine particles size, and stoichiometry of La, Fe and O in LFO is verified by EDAX. The photodegradation behavior of LFO was evaluated by the photocatalytic decolorization of the methylene blue under natural light as well as by UV irradiation for different time. To check the potential of LaFeO3 as dielectric, dielectric constant as a function of frequency and temperature was studied. Dielectric constant is found to decrease with increase in frequency indicates dispersive behavior in low-frequency region. Temperature versus dielectric constant plots for LFO at 100 kHz give dielectric anomaly around 450 °C. This anomaly may be due to antiferromagnetic transition (T N) temperature of LFO. The present study depicts the potential of LFO to use as efficient photocatalyst and applicable dielectric materials. Very good quality and single-phase LaFeO3 (LFO) nanoparticles were prepared first time by microwave-assisted sol–gel combustion method with an aid of glycine as fuel. The photodegradation behavior of LFO was evaluated by the photocatalytic decolorization of the methylene blue (MB) under UV–visible light irradiation. Qualitative understating of correlation between photodegradation ability and dielectric behavior of LFO was established. The potential of LaFeO3 as efficient photocatalyst and dielectric materials is investigated in the present study.

In the present work, the perovkite–spinel interface effect on the bulk magnetic behavior of lanthanum ferrite (LaFeO3) based composite systems is under investigation in view of the enhancement of the magnetization of LaFeO3. By using LaFeO3 as the perovskite phase and NiFe2O4 as the spinel phase with the compositions x = 0, 20, 30, 40 and 100 wt%, a composite system is developed by mechanical mixing. The structures are confirmed using X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Physical interaction at the interface of the LaFeO3 and NiFe2O4 phases is realized by XRD peak broadening and shifting. The M–T and M–H curves are closely monitored to investigate the perovskite–spinel interface effect on the bulk magnetic behavior of the composites. Significant enhancement in the magnetization of the perovskite–spinel composite phase with a 60% LaFeO3–40% NiFe2O4 composition over individual phases is detected. The composition effect up to 60 : 40 of LaFeO3–NiFe2O4 is considered to preserve the dominance of the LaFeO3 phase. The spin coupling mechanism across the interface is speculated for the enhancement of the magnetization in the composite. Mossbauer spectroscopic investigation confirms the co-existence of magnetization in the composites.

In the present work, microwave-assisted coprecipitation route was used for synthesis of nanocrystalline zinc ferrite and results were compared with conventionally prepared zinc ferrite. Synthesis conditions were kept uniform in both cases, except that the mode of heating was changed. The effects of mode of heating on the material properties were studied systematically. Microstructures of both samples were studied by scanning electron microscopy and transmission electron microscopy and the particle size was found to be in the range of 3–4 nm. Particle size distribution in microwave-processed MS-ZnFe2O4 is found to be highly uniform compared to conventionally processed samples (CS-ZnFe2O4). XRD data confirmed the presence of single-phase face-centered cubic structure for both the samples. The XRD data fitted well with Reitveld refinement. The functional groups were analyzed by FT-IR. Local distortions in the structures were studied by FT-Raman spectra of zinc ferrites at room temperature. This study concludes that the microwave-assisted synthesis route reduced the time of reaction by around 23 h and developed uniformly distributed fine-scaled particles. This method has high potential to synthesize other ferrite materials also.

Gd/Sm-modified oxidation state and defect in nano-ceria are studied by X-ray photoelectron (XPS) and Raman spectroscopy technique to investigate their influence on oxy-ionic conductivity of the system. Nanosize Sm and Gd doped ceria (SDC and GDC) are synthesized in different compositions, Ce(1 − x) (Sm / Gd)xO3 − δ (x = 0.05 to 0.30) under identical conditions. XPS study of doped ceria system indicates enrichment of Ce3+ ions in GDC as compared to that in SDC. The quantitative analysis of Raman spectra also predicted the same trend of oxidation state of cerium. The ionic conductivity measurement by electrochemical impedance spectroscopy is demonstrated to verify the results for all compositions of dopant (x = 0.05 – 0.30).

Field cooled (FC) and zero field cooled (ZFC) magnetization measurements of Bismuth Ferrite (BiFeO3) multiferroic obtained by microwave-assisted gel combustion method are reported. The structural investigation of sythesized and calcined sample is done by XRD and the obtained data is well fitted with Rietveld refinement using full-pro software suite. M-H hysterisis shows that BFO nanoparticles exhibit ferromagnetic properties at room temperature, which is unusally observed in BFO. The M-T plot at H = 1 and 2 kOe shows that the FC and ZFC magnetization curve start to differ at below 331K and 236 K respectively with sharp cusp around 124 K revealing spin glass behaviour of BiFeO3. Both ferromagnetic properties and spin-glass-like behavior are observed in BFO nanoparticles. Ferromagnetic behavior is attributed to a partial destruction in nanoparticles of the long-wavelength cycloid spin structure expected in bulk BFO. Spin-glass-like behavior is assigned to diffusion of domain walls, with possible contributions from pinning of the cycloid spin structure at the nanoparticle surface. Copyright © 2014 VBRI press.

Single phase perovskite oxide Pr2FeCrO6 (PFCO) in nanoparticles form was synthesized by low-temperature co-precipitation technique. Structural studies based on the analysis of X-ray diffraction patterns using Pbnm space group show that these nanoparticles exhibit larger structural distortion as compared to their bulk counterpart. Local structural modification due to structural distortion is confirmed through electron density mapping of PFCO nanoparticles. The energy band gap (Eg) obtained from the optical absorption study is 2.13 eV and it is found to be slightly larger than the corresponding bulk system (1.4–2.0 eV). Temperature variation of magnetization shows that these nanoparticles undergo a ferrimagnetic transition at Tc ∼245 K followed by a large irreversibility (87%) under field (1 kOe) cooled condition. The M − H loops recorded at 10 and 50K show the presence of significant remanent magnetization and considerable coercive field due to surface spin canting of nanoparticles.

In the present work, microwave-assisted co-precipitation route was used for synthesis of nano crystalline zinc ferrite for LPG sensing and results were compared with the zinc ferrites prepared by conventional co-precipitation route. For both the synthesis strict uniformity was maintained, while using precursors and conditions of reaction, except mode of heating was changed. Particles size of both samples were confirmed by TEM and found to be in the range of 2–4 nm. The SEM images of microwave proceed ZnFe2O4 (MS-ZnFe2O4) was found to be highly uniform as compared to conventionally proceed sample (CS-ZnFe2O4). XRD data confirmed the presence of single phase face centered cubic structure for both the samples. Functional group was analyzed by FT-IR. Thick films of the samples were made by screen printing and were used for LPG sensing measurement. This study concluded that microwave-assisted synthesis route has reduced the time of reaction by around 23 hr for synthesis of nanocrystalline zinc-ferrites of 2–4 ...

In present work, NiFe2O4(NFO), ZnFe2O4 (ZFO) and Ni0.5Zn0.5Fe2O4 (NZFO) are synthesized by microwave assisted co-precipitation route. Their structural properties are confirmed by X-ray diffraction and data is fitted through Reitveld refinement using Full-Prof software suite. After refinement, the systematic crystal structures of NFO, ZFO and NZFO compounds are generated using output .cif file by VESTA (Visualization for Electronic and Structural Analysis) program. Structural parameters obtained after refinement and unit cell construction, are systematically tabulated. Room temperature frequency dependence dielectric properties are studied. We found enhanced values of dielectric constant for NZFO than individual NFO and ZFO phases. For NZFO sample, greater electron exchange between Fe2+ and Fe3+ which enhances polarization and dielectric constant.

In present work, multiferroic BiFeO3 was synthesized by hydrothermal route. The rhombohedral structure was confirmed X-ray diffraction pattern and data fitted with Reitveld refinement using Full-Prof software suite. SEM micrograph shows flake like morphology. Frequency and temperature dependence of dielectric constant and dielectric loss were studied and detected enhancement in dielectric constant. The magnetic measurement indicates antiferromagnetic nature of BFO. P-E curve shows ferroelectic hysteresis loop with remanent polarization (2Pr) 0.3518 µC/cm2. The dielectric anomaly observed near TN can be assigned to magnetoelectric coupling which is useful in device application.

Magnetic phase diagram of a material could be tuned through structural modication. Here we show significant lowering of magnetic field (Hi) required from transition from cycloidal to canted antiferromagnetic state in sheet like nanostructures of BiFeO3 (BFO), in comparison to reported bulk single crystals of BFO. Structural analysis of this sheet like nanostructured BFO suggests that there is more tilting in FeO6 octahedra that reduce Fe-O-Fe distance in comparison to bulk BFO, leading to decrease in Hi through the reduction of exchange interaction strength.

A microwave-assisted citrate precursor method has been utilized for synthesis of nanocrystalline powders of CoFe2O4. The process takes only a few minutes to obtain as-synthesized CoFe2O4. Structural properties of the synthesized material were investigated by X-ray diffraction; scanning electron microscopy, Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy. The gas sensing properties of thick film of CoFe2O4 prepared by screen printing towards Liquid Petroleum Gas (LPG) revealed that CoFe2O4 thick films are sensitive and shows maximum sensitivity at 350°C for 2500 ppm of LPG.

In the present work, multifunctional behaviors of LaFeO3 (LFO) are investigated by studying its dielectric and photocatalytic properties, respectively. LFO is synthesized by microwave-assisted co-precipitation route. Orthorhombic structure is confirmed by X-ray diffraction (XRD) and data is well fitted using Rietveld refinement by Full-Prof suite. Frequency and Temperature dependence dielectric behavior are systematically studied. The dielectric constant of LFO was found to be 2500 – 3000 with dissipation factor less than 5%. Photodegradation of toxic dye (Methylene Blue) using as-prepared LFO is also investigated. UV-visible absorption spectra are used to study the photodegradation behaviour. Photodegradation of methylene blue (MB) taken from textile industries by LFO are reported. The colossal value of dielectric constant of LFO exhibits high potential to use as room temperature capacitive component for device miniaturization in microelectronics as well as photodegradation ability shows good photocatalyst.

Correlation between atomic positional shift, oxygen vacancy defects, and oxide ion conductivity in doped ceria system has been established in the gadolinium doped ceria system from X-ray diffraction (XRD) and Raman spectroscopy study at operating temperature (300–600 °C) of Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC). High temperature XRD data are used to quantify atomic positional shift from mean position with temperature. The Raman spectroscopy study shows additional vibration modes related to ordering of defect spaces (GdCe′−Vo••)* and (2GdCe′−Vo••)x generated due to association of oxygen vacancies and reduced cerium or dopant cations site (Gd3+), which disappear at 450 °C; indicating oxygen vacancies dissociation from the defect complex. The experimental evidences of cation-anion positional shifting and oxygen vacancies dissociation from defect complex in the IT-SOFC operating temperature are discussed to correlate with activation energy for ionic conductivity.

In the present work, the low temperature infrared absorption spectra of BiFeO3 (BFO) are measured to explore the spin-phonon coupling in this compound. At 303 K, 4 weak transverse optic (TO) IR-active phonon modes E(TO6), E(TO7), E(TO8), and E(TO9) are observed. First two modes are corresponded to the Fe3+ cations caused by the internal vibration of FeO6 octahedra, E(TO8) is correlated to Fe-O bending vibration and E(TO9) is assigned to Fe-O stretching vibrations, respectively. At 213 K, two new modes E(TO5) and A1(TO3) are emerging out. Both are assigned to Fe3+ cations caused by the internal vibration of FeO6 octahedra. These modes get stronger and stronger with lowering the temperature due to the lattice contraction. When the temperatures decreases to T ≤ 213 K, an additional phonon mode is start appearing at around 638 cm−1 suggesting local lattice distortion of FeO6 octahedra. The temperature is corresponding with the FC and zero field cooled bifurcation temperature, which is related to the onset of spin glass behaviour. The occurrence of this additional phonon mode at this particular temperature suggests that there is strong spin-phonon coupling in BFO. This argument is further supported by the temperature dependence of this additional phonon peak. It shows anomaly around 124 K, which is related to spin reorientation of Fe3+ ions. This result clearly indicates that spin glass state and spin reorientation of Fe3+ is accompanied with the local structure distortion of FeO6 octahedra, providing evidence for the strong spin-phonon coupling in the BFO.