Search

Nano-composites of MWCNTs and Ni0.5Zn0.5Fe2O4 were synthesized by two different methods i.e. co-precipitation (CM) and physical-mixing (PM). Properties of synthesized materials were studied by various analytical equipments/techniques viz. X-ray diffraction (XRD), Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM), UV–visible spectroscopy and N5230C vector network analyzer (VNA). The XRD and Raman Spectroscopy confirmed the crystalline phase formation of NZF nano-particles and hybrid NZF/MWCNT nano-composites. The FESEM and TEM images revealed hexagonal flake-like structure of NZF deposited on MWCNTs. The energy band gap of NZF, PM and CM was obtained to be 1.9 eV, 1.3 eV and 1.1 eV respectively. The Electromagnetic interference performance of Ni0.5Zn0.5Fe2O4/MWCNTs nano-composite are reported in the manuscript. The dielectric parameters and EMI shielding effectiveness of nano-materials were carried out by Vector Network Analyzer in the X-band frequency region. The reflection loss value (RL) was calculated and it is observed maximum with a value of −51.2 dB for PM sample at 11.2 GHz. Total shielding effectiveness of 40.1 dB was observed for CM nano-composite in X-band in frequency range 8.2 GHz–12.4 GHz and thus, these composite materials are good for wider applications in electromagnetic absorption devices.

Composites are a class of materials which provide a scope of tailoring properties that are not possible amongst its constituents. Magnetoelectric composite materials exhibit product property arising because of mutually connected electric and magnetic phases. The systematic and comprehensive study on structural, tunable dielectric and flexible energy storage study of NdMnO3 (ND) manganite-based composites has been reported. The phase purity is estimated X-ray diffraction studies and confirm composite formation. The dielectric studies display a step-like decrease and reveal Maxwell-Wagner polarization with relaxation processes. The effect of magnetic field on dielectric constant reveals strong variation due to modification of spatial charge distribution. The qualitative evidence of tunable energy storage studies in ND based composites is observed by measuring the ferroelectric P-E hysteresis loop in variable magnetic field and is strain originated from coupling amongst individual component phases.

Magnetoelectric bulk composites of Co0.5Ni0.5Fe2O4–BaTiO3 (CNFO–BT) were synthesized employing solid-state reaction method. The structural properties of CNFO–BT composites as discussed by X-ray diffraction method confirm lattice distortion and enlarged strain owing to BT substitution in CNFO. The dielectric and impedance measurements exhibit conventional Maxwell–Wagner polarization and confirm the existence of grain dominated non-Debye relaxation phenomena in CNFO–BT composites. The magnetic hysteresis curves reveal strong ferromagnetic behavior in all composites. The maximum energy storage density and an efficiency achieved for 0.8CNFO–0.2BT composite are 4.25 mJ/cm3 and 31.6%, respectively. The variation of polarization with magnetic field confirmed the highest magnetoelectric coefficient of 5 mV/cm/Oe for 0.8CNFO–0.2BT composite. The variation of dielectric permittivity and ferroelectric polarization with magnetic field reveals lattice distortion, interfacial charge polarization and restricted ferromagnetic domain wall rotation arising from substitution of BT in CNFO. These structure-dependent results suggest potential application of CNFO–BT composites in magnetoelectric sensors and energy storage devices.

Multiferroic materials are fascinating to explore due to presence of more than two ferroic orderings in same phase. Ternary materials consisting of more than two constituents are outstanding due to different origin of ferroic orderings. These materials are expected to exhibit strong electric properties due to improved structural stability. The systematic study on structural and impedance properties BiFeO3–BiCoO3–BaTiO3 ternary system has been reported. Structural studies have been investigated using FT-IR spectroscopy and confirms ternary systems formation. The impedance investigations confirm the role of grains and grain boundary in ternary system. The thermal dependent relaxation phenomenon is observed in BiFeO3–BiCoO3–BaTiO3 ternary system. The ternary system also exhibited non-Debye type behaviour.

In this paper, effects of various shapes of filler particles on interfaces formed in the composite have been studied. Detailed mathematical analysis has been carried out for various filler particle sizes, concentrations and interfacial thicknesses considering three shapes of filler particles (spherical, ellipsoidal and disc). It is observed that with the reduction in size of the filler particle, interfacial volume fraction (Vf) increases and this increase is substantial when particle size is below 2 nm to 3 nm.

The choice of electrode’s material, it’s topography like shape, size, and position play a very important role in determination of sensitivity of an electrostrictive capacitive sensor. The electrode material is required to be in mechanical and electrical compliance with the dielectric material for getting optimum performance of the sensor. A mathematical analysis for the estimation of contribution from edge effect has also been carried out for different sizes of electrodes and separation between the electrodes. It has been observed that in capacitive sensors, with gap between electrodes in nanoscale and area of electrodes in millimetres, deviation of capacitance is of the order of 10-3 considering edge leakage as compared to capacitance, measured without considering edge leakage. But in nano range sensors, where both area and gap between electrodes are in nano scale, this deviation is more than 5%, which should not be neglected.

In the present study, the inclusion of 6H foreign polytype was seen during the initial growth of 4H polytype silicon carbide single crystal by PVT technique. The foreign polytype inclusion was gradually diminished with growth time; the mechanism is described in the present paper. In order to study the defects, the SiC specimen was wet etched using KOH solution at higher temperature and it was found that the foreign polytype inclusions i.e. 6H polytype introduced high density of defects at the polytype boundary. The defect distribution in different regions viz. 6H polytype foreign inclusion, 4H polytype region and polytype boundary were found to be different. It is interesting to note that the threading screw dislocation was not seen in 6H-polytype inclusion region.

Material series with compositional formula K0.5Na0.5AxNb1−xO3 (x is ranging from 0.00 to 0.06) were prepared where A is transition metal Mn. Pure perovskite phase with orthorhombic structure of K0.5Na0.5MnxNb1−xO3 compositions was confirmed from XRD. The lattice parameters (c, a) were found to increase with Mn content. The dielectric constant (e) was observed to increase with substitution of Mn at room temperature. The dielectric constant increased with temperature for K0.5Na0.5MnxNb1−xO3 with x ≤ 0.04 compositions and decreased for x > 0.04. The maximum dielectric constant emax = 4517 at Tc = 421 °C at 100 kHz frequency was achieved for x = 0.02 composition. The piezoelectric constant (d33) was found 178pC/N for 2% Mn substitution.

The development of electronic technology is flexibly related to the progresses made in material science. Functional materials out of the broad class of materials available today offer unique chance for developing novel components and devices. In this framework, provides a new class of functional materials, the multiferroics (MFs), combine two or more different ferroic orders (viz. ferroelectric, ferromagnetic and ferroelastic) in a single phase and are utilized in a broad range of systems. In connection with multiferroism, a broad category of materials namely magnetoelectrics allow the electric control on magnetization or vice-versa are explored extensively. Even though, the research in the field of MFs and magnetoelectric (ME) materials can be traced back to revolutionary research in the early 1950s. There has been a contemporary resurgence of concern motivation by long-term technological aspirations. The center of attention of this review is on elementary understanding of the MFs and ME materials using a multidisciplinary approach to address the underlying mechanism responsible for the coupling, their applications in some novel devices, new opportunities and future challenges.

Thin films of polycrystalline single phase α-Fe2O3 have been deposited on single crystal silicon and amorphous silica (silica) substrates by spray pyrolysis technique in a single step using a mixture of water and ferrocene dissolved in xylene. The films have been characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy techniques. The uniformity of the grown films was evident from the electron microscopic images on both the substrates. The crystallinity and band gap were investigated using X-ray diffraction and absorption spectroscopy respectively. Raman measurements of the prepared films have been carried out using two excitation wavelengths of 633 nm and 785 nm to investigate the depth of homogeneity of the films. The wavelength dependent Raman measurements reveal that the film is uniform across the thickness of the film on both the substrates.

Generally, it is very difficult to grow large diameter 4H-SiC single crystal with single polytype by Physical Vapor Transport (PVT) growth method and mostly it ends up with the presence of some other polytypes (viz. 6H, 15R). This paper presents the various comprehensive polytype identification techniques in SiC wafer grown by PVT method. Characterization techniques, viz. X-Ray diffraction, Scanning electron microscopy, Cathodoluminescence (CL) and Raman spectroscopy, are used in the present study in order to identify the presence of 4H, 6H and 15R polytype region in SiC wafer. Raman mapping (using phonon frequencies at 150, 171, 203 cm−1 for 6H, 15R and 4H, respectively) and X-Ray Topography [using grazing incidence asymmetric plane (11–2 8) for 4H-SiC, (11–2 12) for 6H-SiC and (11–2 30) for 15H-SiC] and CL spectra (defect state peak positions at ~ 500 nm and 580 nm for 4H and 6H, respectively) are proposed to distinguish the switching of polytypes in a large area SiC wafer. The polytype switching in SiC ingot may occur because of temperature fluctuations during the sublimation growth process.

A comprehensive study was conducted to analyze the structural, dielectric, impedance spectroscopy and conductivity of Bi0.95Gd0.05FeO3–BaTiO3 (BGF-BT) solid solutions, synthesized via. solid state reaction route. BGF-BT solid solutions show pseudo-cubic structure corroborated by X-ray diffraction patterns and Rietveld analysis. Scanning electron microscopy morphology confirmed that the average grain size decreases with an increase in BT content into BGF. A further insight into the valence chemical states was provided by the core and survey scan of binding energy using the X-ray photoelectron spectroscopy (XPS). The spin-orbit interaction energy in BGF-0.3BT for Fe2p and Bi4f was estimated at 13.3 eV and 5.3 eV respectively. The decrease in oxygen vacancies on incorporation of BT into BGF is also verified after analyzing O 1s core spectra. Raman Spectroscopy also confirmed the chemical bonding and structure of BGF-BT solid solution samples. Maximum magnetization of 1.4047 emu/g was observed for BGF-0.1BT as validated from magnetization hysteresis loops and ferroelectric P vs. E loop measurement confirms the ferroelectric nature of the BGF-BT samples. Analysis of dielectric properties at fixed frequencies confirmed the evidence of magnetoelectric coupling through the broad dielectric anomaly near the reported magnetic transition temperature in BGF-BT samples. The dielectric and impedance spectroscopy studies also confirmed the non-Debye type relaxation phenomenon in the BGF-BT samples. Conductivity measurements followed Jonscher's power law whose experimental fitting determined the pre-factor (A) i.e., polarizability strength and frequency exponent (n). Low activation energy values, 0.187 eV, 0.108 eV and 0.131 eV for BGF-0.1BT, BGF-0.2BT and BGF-0.3BT solid solutions, respectively were observed, show the indication of mobility of defects present in lattice and associated with the hopping conduction mechanism.

Multiferroic magnetoelectric composites are beneficial in device fabrication because of their tunable ferroelectricity and magnetism. The partial substitution in bismuth ferrite (BiFeO3) is one of the best possible ways for synthesizing pure phase BiFeO3-based materials. A comprehensive study of (1 − x)Bi0.85La0.15FeO3–xBaTiO3 (x = 0–0.3) was done by coalescing ferroelectric, dielectric, magnetic, and magnetoelectric properties with structural and microstructural characterizations to explore the effect of BaTiO3 (BT) into Bi0.85La0.15FeO3 (BLFO) and forming composite ceramics. The X-ray diffraction study reveals the phase purity in BLFO and a structural transformation from rhombohedral to cubic phase with increasing content of BT. The Raman spectroscopy and scanning electron micrographs confirm the co-existence of composite formation in BLFO–xBT. The Raman modes shift towards lower wavenumber with increasing BT concentration suggests lattice compression. The room temperature M–H hysteresis curve shows the existence of weak ferromagnetism in BLFO–BT composites and superparamagnetism in BLFO–10BT ceramic. The curve fitting of M–H curve for BLFO–10BT showed the existence of superparamagnetic particles. The ferroelectric hysteresis P–E loop measurements produced unsaturated oval-shaped loops with high leakage and displayed a lossy dielectric nature. The effect of magnetic field on polarization versus electric field curve reveals the interfacial interaction due to the origin of magnetoelectric interaction in BLFO–BT composite ceramics. All the samples display peak broadening in temperature–permittivity plot and confirm relaxor behavior. The superparamagnetic behavior and magnetic field-dependent energy storage capacity of BLFO–10BT composite ceramic make this material a potential candidate for magnetoelectric devices.

In the present work, crystal structure and field-induced bipolar strain response of Pb-free (Bi1−xGdx)0.5Na0.5TiO3 (BNT:Gd) ceramics with x ≤ 0.04 were investigated systematically. Pure perovskite phase exhibited without any notable change in the crystal structure within the range of specimen studied. Structural analysis of BNT: Gd ceramics was performed through Rietveld refinement by Fullprof software. Rhombohedral structure with space group R3c had been confirmed for x ≤ 0.04. Electric field-induced strain showed a butterfly characteristic of bipolar strain hysteresis curve for the composition x ≤ 0.04 in BNT: Gd ceramics at RT. The maximum normalized piezoelectric strain coefficient d*33 of 148 pm/V was obtained in BNT: Gd systems which is approximately 4.9 times greater than static piezoelectric constant d33 (30pC/N) for the specimen x = 0.04.

The present paper deals with the new record of fungal remains from the Subathu Formation exposed along Dogadda-Kotdwar road section in Dogadda, Uttarakhand. The assemblage is composed of 13 species assignable to 10 genera. The important genera are Callimothallus senii, Haplopeltis mucoris, Haplopeltis sp., Parmathyrites sp., Phragmothyrites eocaenicus, Plochmopeltinites sp., Spinosporonites saxenae, Spinosporonites angularis and Trichothyrites padappakkarensis. The presence of microthyriaceous fungi in dominance suggests that the region experienced a warm and humid climate during the course of sediment deposition with thick vegetation providing suitable substrates for the growth and proliferation of fungi. Their presence depicts the prevalence of moist tropical type of vegetation during deposition in the area. The present fungal assemblage is assigned Late Palaeocene-Middle Eocene age.

(1-x)BiFe0.75Mn0.25O3-(x)BaTiO3 (x = 0.1, 0.2, 0.3) solid solutions have been prepared utilizing conventional solid state reaction route. Powder XRD study confirmed the structural evolution from rh...

Magnetoelectric composites combining ferromagnetic cobalt ferrite (CFO) and ferroelectric barium titanate (BT) are prepared using conventional solid-state reaction. Dielectric measurements reveal that CFO and CFO-BT composites exhibit Maxwell–Wagner polarization and temperature-dependent relaxation originating due to the presence of ions/defects vacancies. Prominently, CFO-30%BT composite showed an unexpected low dielectric loss ≈ 0.5 above 1 kHz and has potential for device application. Impedance spectroscopy confirms the thermally activated relaxation mechanism and high impedance behavior in the samples. Modulus analysis affirms the statistically distributed non-Debye-type behavior existing in CFO-BT composites. The electric conductivity takes place via correlated barrier hopping in CFO and CFO-10BT composite and overlapping large polaron tunneling in CFO-30BT composite. The addition of BT in CFO initiates the structural modification and results in conductivity cross-over with improved conductivity. These results are useful for exploring devices based on CFO-BT composites.

Two phase magneto-dielectric composite of Barium titanate and Cobalt ferrite (BT-CFO) has been prepared via solid state reaction technique. The structure has been investigated by Raman spectroscopy and confirms the presence of composite phase. Electrical properties of BT-CFO composites were studied thoroughly in 100 Hz to 1 MHz frequency range and in 50 °C–450 °C temperature range. The dielectric measurements reveal Maxwell-Wagner polarization and thermal activated relaxation process arising from movement of defects and ions in BT and BT-CFO composites. Particularly BT-5CFO composite exhibited a surprising low dielectric loss ≈0.3 over the frequency range of 100 Hz-1MHz and promises industrial application. The thermal variation of Impedance parameters reveals the resistive nature of the composites and the presence of two thermally activated relaxation mechanism present in BT and BT-CFO composites. The modulus studies confirm the non-Debye type relaxation processes prevalent in BT-CFO composites. The electrical conduction mechanism occurs through over-lapping large polaron tunneling (OLPT) in BT and through non-overlapping small polaron tunneling (NSPT) at low temperatures to correlated barrier hopping (CBH) at high temperatures in BT-CFO composites. The addition of CFO in BT localizes the polarons and enhances the conductivity. The magneto-dielectric coupling effect (% MD) is found to have a maximum value of 1.2 in magnitude at 7 kOe for BT-5CFO composite and increases with the amount of CFO in BT-CFO composite. These results could be beneficial in enhancing the properties of BT-CFO based systems.

Enhanced magneto-electric coupling and energy storage density analysis of solid-state route derived (BiFeO3–BaTiO3)/CoFe2O4 composites were investigated for memory application under the variation of the magnetic phase of CoFe2O4. The powder X-ray diffraction data, SEM–EDX, Raman spectroscopy, and FTIR measurements were carried out to investigate the crystalline structure, composite formation and phase purity of all the samples. Magnetic measurements showed very high magnetization values obtained from 0.063 emu/g for 0.7BF–0.3BT to 18.14 emu/g for (0.7BF–0.3BT)/30CF composite near room temperature. The weak but countable maximum ferroelectric polarization (Pmax) was achieved due to the change in the area of the loops with the variation of frequencies from 50 to 200 Hz. The highest value of energy storage density (Ju) and efficiency (η) for (BF–BT)/30CF (Ju = 37.08 mJ/cm3 and η = 89.40%) composite was achieved. The dielectric anomaly near the magnetic transition temperature (Tc ~ 425 °C) and the variation in the maximum polarization values from 4.63 to 6.6 µC/cm2 with respect to the applied magnetic field confirmed the strong evidence of magneto-electric coupling in (BF–BT)/CF composite samples. The highest values of magneto-electric coefficients (α) were achieved 9.039 mV/cm Oe at 600 Oe, 9.039 mV/cm Oe at 1100 Oe and 22.59 mV/cm Oe at 1600 Oe for (BF–BT)/10CF, (BF–BT)/20CF and (BF–BT)/30CF composites respectively.

The present work is focused on the structural, microstructural, dielectric, multiferroic properties, including magnetoelectric coupling and energy storage density analysis of Mn modified multiferroic BiFeO3 (BFO) samples. The samples were prepared via solid state reaction method. The structural and microstructural properties were investigated using powder x-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The single phase of Mn modified multiferroic BFO was confirmed from XRD patterns which exhibited predominantly a majority phase of BFO. SEM micrographs indicated decrease in grain size and more homogeneous grain structure with the increase of Mn content into the BFO. A nonzero value of coercivity was obtained in the 5% Mn BFO (BFMO5) sample, which confirmed the antiferromagnetic to weak ferromagnetic change. Composition dependent P versus E ferroelectric hysteresis loop measurements confirmed the enhanced ferroelectric nature of the samples. An enhanced value of energy storage density (13.71 mJ/cm3 and 34.86 mJ/cm3) was achieved for BFMO3 and BFMO5 samples. The frequency dependent and magnetic field dependent measurements of P versus E hysteresis and dielectric anomaly near the magnetic transition temperature confirmed qualitative, as well as quantitative, magnetoelectric (ME) coupling, including the maximum value of ME coupling coefficient (α ≈ 3.36584 mVcm−1 Oe−1 at a field of 2696 Oe) obtained for the BFMO5 sample. Enhanced values of dielectric and impedance parameters were observed in the Mn modified BFO samples.

This paper presents an investigation on micropipe evolution from hexagonal voids in physical vapor transport-grown 4H-SiC single crystals using the cathodoluminescence (CL) imaging technique. Complementary techniques optical microscopy, scanning electron microscopy, and energy-dispersive spectroscopy (EDS) are also used to understand the formation mechanism of hexagonal voids along with the origin of pipes from these voids. The ability of CL to image variations along the depth of the sample provides new insights on how micropipes are attached to hexagonal voids that lie deep within the bulk single crystals. CL imaging confirms that multiple micropipes can originate from a single hexagonal void. EDS mapping shows that the inside of the micropipe walls exhibits higher levels of carbon. Investigation of the seed region by optical imaging shows that improper fixing of the seed to the crucible lid is the root cause for the formation of hexagonal voids that subsequently lead to micropipe formation.

Multiferroics are the materials possessing two or more ferroic orderings viz. ferroelectric, ferroelastic, ferromagnetic or ferrotoroidic. Magnetoelectric coupling requires manipulation of electrical ordering via magnetic field or vice versa. In this work, the magnetoelectric composites of (1-x)Co0.5Ni0.5Fe2O4-xBaTiO3 (CNFO-BT) (x=0.3 and 0.5) were prepared employing solid state reaction method. The structural measurement of CNFO-BT composites employing X-ray diffraction technique confirm single phased nature of cubic and tetragonal phase with space group Fd3m and P4mm for CNFO and BT phases respectively. The magnetodielectric change exhibit robust non-zero coupling even at magnetic field of 6 kOe. The ferroelectric measurements show improvement in CNFO-BT composites with increasing amount of BT due to enhanced electrical properties. The magnetic hysteresis curves reveal strong ferromagnetic behavior in all composites. These measurements establish the multiferroic and magnetoelectric nature of CNFO-BT composites.

Ferroelectric–magnetic composites of SrBi2Nb2O9–CoFe2O4 (SBN–CFO) were synthesized via conventional solid state reaction route. The powder X-ray diffraction, Raman spectroscopy and scanning electron microscopy measurements confirm the existence of two chemically separated phases and phase purity in the SBN–CFO composites. Magnetization measurements confirm the enhanced values of the magnetic parameters. The change in the area of the ferroelectric P vs. E loops with frequency confirms the enhanced ferroelectric nature of the SBN–CFO composites. The quantified maximum values of magnetoelectric coefficient (α) are observed from the P vs. E loop measurements in the influence of applied magnetic field and found to be 4.475 mV cm−1 Oe−1 at 688 Oe for SBN–0.1CFO and 3.389 mV cm−1 Oe−1 at 1000 Oe for SBN–0.2CFO composites, respectively. The shifting in the peaks of temperature-dependent dielectric maxima towards the higher temperature side confirms the relaxor behaviour in the SBN–CFO composite samples.

The ternary compound BiFeO3–BiCoO3–BaTiO3 (BFO–BCO–BT) was prepared using the solid-state reaction method. The dielectric studies display strong frequency-dependent anomaly in the vicinity of Curie temperature (TC) ≈ 350 °K and exhibit strong diffusive relaxor behavior with (γ ≈ 1.61). The dielectric measurements confirm stabilization in BFO–BT solid solution due to BCO addition. The P–E loops display strong ferroelectric behavior and frequency variation indicating major dominant domain wall movement on high dielectric constant in the BFO–BCO–BT ternary compound. The magnetic field variation in the P–E loop displays strong magnetoelectric coupling originating from interfacial polarization with maximum coupling coefficient of 115 mV/cm-Oe at field of 500 Oe. The temperature variation of P–E shows enhanced configurational entropy due to increase in activation energy, with the highest isothermal energy (ΔS) = 0.15 J/kg/K obtained for E = 15 kV/cm and T = 125 °C. These studies provide tunable ferroelectric properties of BFO–BCO–BT for exploration of promising applications such as refrigeration and magnetoelectricity.

A unique averaging mechanism is established for estimation of magnetoelectric coupling coefficient (α) by studying the effect of magnetic field on ferroelectric hysteresis loop measurements. The highest value of α obtained using this mechanism is 22 mV/cm/Oe at a field of 5000 Gauss for CoFe2O4-10%BaTiO3 (CFO-10BT) composite and is in agreement with the recent reported studies. The composites of CFO-BT exhibit interplay of magnetism, ferroelectricity and display strong magnetoelectric behaviour arising out of charge disordering. The structural studies from the combination of XRD, Raman and FTIR measurements of CFO-BT composites establishco-existence of cubic and tetragonal phase with space group. The ferroelectric studies display a low leakage charge density of 0.0031 μC/cm2 and prevalent asymmetry arising due to spatial disordering of charge distribution. Furthermore, the magnetic measurements reveal an enormous increase in the coercivity of CFO-30BT composite which is identified in terms of movement of ferromagnetic domains arising due to inclusion of trapping centres of BT in CFO.

BiFeO3–CoFe2O4 composites were successfully prepared via conventional solid state method. Powder X-ray diffraction confirmed the presence of both perovskite BiFeO3 (BFO) and spinel CoFe2O4 (CFO) phases and rhombohedral structure due to splitting in major peaks in the composites. Further insight into the microstructural and morphological properties of the composites was provided by Raman spectra, Fourier Transform Infrared Spectroscopy and Field Emission Scanning Electron Microscopy along with EDX analysis. Magnetic and electrical response of the composites has been studied exhaustively to comprehend their multiferroic properties. Magnetization study (magnetization vs. magnetic field) confirmed the high saturation magnetization in composites with a low value of coercivity at room temperature. The maximum saturation magnetization (0.3902 emu/g) was achieved in BFO–30%CFO. Ferroelectric polarization (polarization vs. electric field) loop measurements confirmed the low electrical leakage current in the composites. The temperature dependent dielectric response of the composites suggested existence of magnetoelectric coupling between the ferroelectric and ferromagnetic orders in the vicinity of antiferromagnetic–paramagnetic transition temperature of BFO. The decrease in dielectric loss with an increase in CFO content in the composites also validated the similar results as observed in polarization versus electric field measurements. The Impedance Spectroscopy at room temperature revealed the non-Debye behavior and high resistivity of the composites.

Ferroelectric–ferrite composites of BaTiO3–CoFe2O4 (BT–CFO) is synthesized via solid state reaction method. Powder XRD confirms the phase purity as well as composite formation with tetragonal phase of the BaTiO3. The FTIR and SEM–EDS studies also confirm the formation of BT–CFO composites. The P–E loop measurement confirmed the ferroelectric nature of the sample. The maximum energy storage density and efficiency achieved for BT–5CFO (5% CoFe2O4) composite was 8.33 mJ/cm3 and an efficiency of 59.7% respectively. The coupling between the ferroelectric and ferromagnetic phases was observed in the variation of P–E loop with magnetic field. A decrease in the maximum polarization was found with increase magnetic field. The P versus M analysis confirmed the highest magneto-electric (ME) coefficient of 13.33 mV/cm/Oe for BT–5CFO composite. These results are related to the volumetric and piezoelectric strain, suppression of ferroelectric ordering reveal the magnetoelectric nature in BaTiO3–CoFe2O4 composites.

In this paper, we reported the results of structural and electrical properties of Pr1–xEuxMnO3 (PEMO; x = 0.10, 0.30 and 0.50) manganites, synthesized by conventional solid-state reaction method. Structural studies revealed a mixed-phase nature (with some impurity phase) in all PEMO samples, having a rhombohedral and orthorhombic structure. The unit cell volume decreased slightly with Eu content in PEMO ceramics. The dielectric and impedance measurements were conducted in the temperature range of 25–450 °C and frequency range of 50 Hz to 4 MHz. The low values of activation energy (0.278, 0.138 and 0.017 eV for x = 0.10, 0.30 and 0.50, respectively) showed the presence of oxygen vacancies. Cole–Cole plot demonstrated that the grain boundary effect diminished with increasing temperature. This was due to the development of oxygen vacancies during sintering at higher temperatures. These defects influenced the impedance at the barrier of the grain and grain boundary interface.

In the present study, lead-free piezoelectric (1-x)[(Bi 0.96 La 0.04 ) 0.5 Na 0.5 TiO 3 ]-(x)[Ba 0.90 Ca 0.10 TiO 3 ] ceramics with x ≤ 0.20 have been prepared at optimum temperature (950°C–1050 °C) by employing semi-wet technique. The effect of Ba 0.90 Ca 0.10 TiO 3 (BCT) content on the phase formation, surface morphology, dielectric and piezoelectric properties is systematically investigated and characterized by X-ray diffraction (XRD), Raman Spectroscopy, Field emission Scanning electron micrographs (FE-SEM), Impedance analyzer. XRD analysis shows phase transformation from rhombhohedral to tetragonal with the addition of BCT and the average grain size decreases with BCT content, x. Temperature dependent dielectric behavior exhibits two phase transitions, i.e. depolarization temperature; T d and phase transition temperature; T m . The phase transitions; T m tends to diffuse with increasing x and exhibited a broad frequency dependent maximum upto x ≤ 12. Optimum piezoelectric and dielectric properties (i.e., d 33 = 165 pC/N, k p = 39%, k t = 47% and k 33 = 57%, e r = 1585, tan δ = 0.07) in the studied system have been obtained.

Mn0.5Zn0.5X0.2Fe1.8O4 (X = Fe, Gd, La, Sm) nano-ferrite were synthesized by chemical co-precipitation method. Magnetic measurements for the synthesized Mn0.5Zn0.5X0.2Fe1.8O4 (X = Fe, Gd, La, Sm) nano-particles were recorded at temperatures 10 and 300 K. Magnetic moment per unit formula in terms of Bohr magnetron (μ B) was calculated from magnetization data of hysteresis loops. Particle size was calculated from the magnetization data for all compositions of Mn0.5Zn0.5X0.2Fe1.8O4 (X = Fe, Gd, La, Sm) ferrite particles.

History has always been a perennial source of man's keen curiosity and great interest. An ever-growing significance of Geosites, museums, monuments and sites of archaeological importance, the world over, is evidence to it. The tremendously growing tourism industry, in fact, has its origin in this very fact. Of late, alongside the concept of theme parks, the innovative idea of exploring the important sites revealing specific events (climatic, tectonic, thermal, magmatic, geomorphic, extra-telluric etc.) through geological history or associated with the evolution of mankind and the present day biodiversity as well, through the earth history of 4.6 billion years and also using them as a potential tourist resource is steadily getting ground. If exploration of prehistoric geosites and development of important sites for information, education and awareness of people could be judiciously integrated with tourism promotion, it may have synergistic implications as the sites would act as a unique touristic appeal and the tourism itself will support the former concept financially and otherwise, as well. India, on account of its unique geological history vis-a-vis physiographic, biotic and geoheritage manifestations of varied geo-events and consequently meteorological differences prevailing in, is one of the richest repository of varied geo-heritage sites including bio-sites studded with record and documentation of evolutionary lineages essentially needed to unravel the history of earth and understanding the palaeo-prevailed environmental scenario through earth's history and intensity of natural processes operating upon ever since the earth's origin. The present paper aims at comprehensively examining the prehistoric geosites in India, in an attempt to identify some of the areas with richer heritage in this regard. Some of the geologically more important sites with rich geoheritage and also prominent areas of tourism promotion are discussed in this paper, so as to conserve this invaluable treasure of earth history in the today's era of squeezing space on the face of rapid Industrialization and infra-structural developmental activities.

Multiferroic composites are advantageous from technological perspective because of their flexible electrical and magnetic properties. The multiferroic composites of (1-x)NdMnO3 – (x)BaTiO3 (x = 0, 0.1 and 0.2) were synthesized via solid state reaction method. The structural analysis from XRD studies of (1-x)NdMnO3-(x)BaTiO3 exhibits distinct peaks of orthorhombic NdMnO3 (NMO) and tetragonal BaTiO3 (BT) phases with absence of any other impurity phases in the composites. The frequency variation of dielectric measurements reveals step-like decrease and confirm Maxwell-Wagner Polarization associated with improved conducting nature in NMO-BT composites. The NMO-20BT composite exhibited giant dielectric behavior owing from lattice stability and hopping mechanism. The impedance measurements confirm improved resistivity in NMO-BT composites and confirm thermally activated non-Debye type conduction behavior in NMO-BT in them. The occurrence of saturated ferroelectric polarization composites along with enhanced remnant magnetization and improved magnetoelectric coupling in NMO-20BT composite due to lattice stability establishes multiferroism in NMO-BT composites.

We have synthesized lead-free BZT-xBCT (x = 0.45, 0.50 and 0.55) compositions near morphotropic phase boundary (MPB) using sol-gel technique. Here, we have reported the compositional effect of BCT concentration on structure, surface morphology, dielectric properties and energy storage capacity of BZT-xBCT ceramics. Scanning electron microscopy analysis suggests that the smallest grain size is found for the x = 0.55 composition. The dielectric constant vs temperature measurement indicates that the addition of BCT causes lowering of ordering temperature. In addition, we have performed modified Curie-Weiss fitting to reveal the microscopic behaviour of the synthesized compositions and found Curie constant ‘C’ as 1.3 × 10 6 , 2.1 × 10 7 and 1.7 × 10 7 for x = 0.45, 0.50 and 0.55 compositions, respectively, and diffusion coefficient 1.4 ≤ γ ≤ 1.99 . Polarization (P) vs electric field (E) curves collected at series of temperature, insights that compositions x = 0.50 and 0.55 exhibit slimmer P-E profiles, which causes lowering of remnant polarization (Pr) and hysteresis loss of dielectric system and ensures their suitability in area of pyroelectric based energy harvesting. We also estimated the energy storage density W~189 mJ/cm3 and high discharge efficiency η~75.6% for BZT-0.55BCT ceramic composition. Further, we have employed Arrott plot approach to reveal the involved mechanism of Landau Free Energy flattening in BZT-BCT composition at MPB. It is considered that Landau Free Energy flattening plays key role in exhibiting high electro-mechanical response at MPB. On the basis of findings from dielectric spectroscopy and Arrott plot scheme, we argue that energy flattening phenomenon and high electromechanical response in BZT-xBCT system is achieved via active “polarization rotation mechanism”, instead of “polarization extension”. Our study emphasizes that BCT rich BZT-0.55BCT ceramics are suitable for high energy storage density application.

The present study reports the structural, magnetic, dielectric, transport, and electronic properties of Nb substitution in the multiferroic (0.7-x)BiFeO3-0.3BaTiO3-xNb2O5 solid solution. Rietveld refined x-ray diffraction results confirm the perovskite phase formation along with a transformation in the structural symmetry, which exhibit a monotonous enhancement in the unit cell parameter with Nb substitution and a monotonous increase in the lattice parameters is observed with increased Nb concentration. Subsequently, scanning electron micrographs and Raman spectroscopy substantiates these structural changes. Interestingly, magnetic ordering temperature and net magnetization enhanced remarkably for the Nb substituted samples and a maximum value of saturation magnetization (1.95 emu/g) is accomplished for x = 0.10, which is significantly higher as compared with 0.11 emu/g for the parent compound (x = 0). A large value of remanence magnetization (0.8 emu/g) for the highest Nb-dopant (x = 0.10) is obtained as compared to other transition metal-doped BF-BT systems, which make it very useful in memory device applications. Two dielectric anomalies within the temperature ranges of 200 ≤ T ≤ 400 °C and 400 ≤ T ≤ 500 °C appear due to Nb substitution in the BF-BT phase. The phenomenon of dielectric relaxation with a larger dielectric constant was observed near the Curie temperature. Temperature-dependent dielectric and magnetic study confirm the coupling between electric and magnetic dipoles in all Nb substituted samples. Impedance spectroscopy results within the frequency (100 Hz ≤ υ ≤ 1 MHz) confirm Debye-type behavior and maximum bulk resistance of ~110 kΩ for x = 0.10. Conductivity data follow Jonscher's power law and confirms that the conduction phenomenon is dominated by the mechanism of charge carriers hopping. Arrhenius model estimate the values of activation energies for x = 0, 0.03, 0.05, and 0.10 samples to be 0.61, 1.12, 1.08, and 1.22 eV, respectively. Room temperature x-ray photoemission spectroscopy measurements for the constituent Bi, Ba, Ti, and Nb elements exhibit that they exist in their 3+, 2+, 4+, and 5+ valence states, respectively, which do not alter with the increased Nb substitution. The core-level spectra of Fe 2p manifest a complex multiplet structure and confirms its trivalent state in the samples.

Multiferroic BiFeO 3 (BFO), La/Co modified BiFeO 3 (BLFO/BLCFO) ceramics prepared by solid state reaction route were characterised and their magneto-dielectric properties were investigated. The phase purity of La/Co modified BFO ceramics was confirmed from powder X-ray diffraction studies and distortion observed in the lattice due to compression was found to be associated with polarization switching on La/Co co-substitution into BFO. An enhancement and stability in saturation magnetization with low coercive field (H c ≈ 400 Oe) has been achieved at room temperature in La/Co modified BFO samples. Dielectric and impedance measurements reveal the enhanced values of dielectric constant, real and imaginary part of impedance and modulus on account of modification by La/Co in BFO. The modulus studies confirm the presence of ionic polarization due to the co-substitution of La 2+ /Co 3+ ions and dominant grain effects in BLFO and BLCFO samples. The magneto-dielectric effect (% MDE) is found to be maximum value of 1.8 in magnitude at 8 kOe for BLFO-10%Co, and increases with increase in Co content in to BLFO. The substitution of Co into BLFO generates polarization at La and Fe layer, which provides the enhanced value of %MDE and stability in purity of BFO ceramic.

Cadmium doped barium zirconate titanate (Ba 1−x Cd x )(Zr 0.13 Ti 0.87 )O 3 (BCDZT) ferroelectric ceramic compositions with x =0, 0.02, 0.04 and 0.06 have been prepared by solid state reaction method. X-ray diffraction studies reveal a pseudocubic structure. For increasing Cd content, the bulk ceramic micro-structure reveals an increasing grain size and density. Variations in the dielectric, piezoelectric and unipolar electric field induced strain characteristics are discussed. Increasing Cd content reduces the coercive field, increases the remnant polarization and does not affect the ferroelectric-paraelectric phase transition temperature (~60 °C). An optimum Cd content x =0.06 produces highly resistive ceramics with low dielectric loss (tan δ =0.019), and a maximum value of piezoelectric charge constant d 33 =114 pC/N and unipolar electro-strain of ~0.07%.

Effects of Zn2+/La3+ co-doping on multiferroic and impedance properties of co-precipitation derived Co1−xZnxFe2−xLaxO4 (x = 0.0, 0.1 and 0.3) nanoparticles have been investigated. The powder X-ray diffraction study confirms the pure phase, cubic spinal structure and particle size varies between 20 and 22 nm. The particle size decreases with increase in co-substitution indicating the short range ordering in CoFe2O4. The relaxations in dielectric constant follow Maxwell–Wagner polarization and arise out of charge transfer of Co and Fe ions in multi-oxidation states. The co-substitution of Zn2+/La3+ in CoFe2O4 at A and B sites respectively results in improvement of Nquist plot and impedance of the nanoparticle which confirms space charge polarization caused by piling of charges at the interface of grain and grain boundries. An unusual relaxation behavior is also observed in co-substituted CoFe2O4 which may be useful in enhancing the multiferroic properties at room temperature. It could be noted the GBs are more resistive as compared to the grains, resulting in high impedance value and non-Debye type behavior in the Co1−xZnxFe2−xLaxO4 nano particles. Low and stable coercivity (Hc) of 393.13 Oe have been observed and a stable saturation magnetization has been achieved at room temperature. P–E loops have rounded corners which may be the due to the aggregation of CoFe2O4 nanoparticles with each other resulting out of their strong magnetization. Simultaneous occurrence of saturation magnetization and weak ferroelectricity (P–E loop) with high values of impedance and dielectric constant confirm the signature of multiferroicity in Co1−xZnxFe2−xLaxO4 nanoparticles.

Modified ceramic compositions of Bi3.79Er0.03Yb0.18Ti3−xWxO12 with fixed Er and Yb content, and a varying W content (x=0.0, 0.01, 0.03, 0.06 and 0.10) are prepared. The site selectivity of Er3+, Yb3+, and W6+ cations is analyzed, and their influence on the electrical and light up conversion properties is studied. Formation of single phase orthorhombic structure is confirmed with enhanced grain growth up to x=0.03, and for (x≥0.04–0.10) the grain growth is inhibited, and the orthorhombic distortion is relaxed. Raman spectroscopy reveals W6+ cation substitutes preferentially at the B-site replacing Ti4+ ions in the Bi4Ti3O12 lattice structure. Increasing W6+ donor concentration reduces the conductivity effects by lowering the oxygen vacancies. Reduced dielectric losses (tan δ=0.003) and dispersion with frequency in the range (10−2–10 Hz) are observed, and improvements in the remnant polarization (2Pr=28.86 μC/cm2) are seen up to an optimum content of x=0.03. At higher W content (x>0.03), the properties tend to degrade due to structural relaxation and microstructural changes. Up conversion photoluminescence (UC-PL) under 980 nm excitation shows strong emission in the green and red bands due to enhanced crystal field around the Er3+ ions for an optimum W content of x=0.06. A weak blue emission band around (~492 nm) is observed by cooperative emission (CE) due to radiative relaxation of an excited Yb–Yb pair from a virtual level. Variation of UC emission intensity with pump-power confirms a two-photon mechanism for the up conversion process.

Nanocomposites of La0.7Sr0.3MnO3–PbZr0.52Ti0.48O3 (LSMO–PZT) were synthesized by sol–gel route. The powder X-ray diffraction study confirmed the phase purity and the particle size (≈30–34 nm) of the nanocomposites. Magnetic, dielectric and magneto-dielectric studies of LSMO–PZT nanocomposites reflected a coupling between dielectric and magnetic parameters near the magnetic transition temperature (Tc ≈ 360 K). The quantitative magneto-dielectric coupling was found to be maximum value of 1.34 in magnitude at 1.5 T and decrease with increase in frequency. This provides the signature of magneto-dielectric coupling qualitatively as well as quantitatively in LSMO–PZT nanocomposites.

Ferroelectric PZT-PVDF composites (0–3 connectivity) of specific dimensions were made utilizing a hot press technique. Linear variation in the experimental density of the pellets made from 0.1 to 0.8 PZT volume fraction was observed. The surface morphology of the composite has been micro-graphed using SEM. The variation of the dielectric properties of the composites on PZT volume fractions is reported and analyzed. It is observed that there was an increment in dielectric constant (ϵr) with an increase in temperature and volume fractions. The piezoelectric strain coefficient (d33) increases with an increase in the volume fraction and voltage coefficient (g33) were calculated. Comparisons were made with the Furukawa model to ϵr and d33. The remnant polarization and coercive field were analyzed from the hysteresis plots.